ESSENTIAL
C o l o r e d
S t o n e
Reference Guide
3/2014
©
© 1999 The Gemological Institute of America
All rights reserved: Protected under the Berne Convention.
No part of this work may be copied, reproduced, transferred, or transmitted in any form or by any means whatsoever without the express
written permission of GIA.
Printed in the United States.
Reprinted 2006, 2014
Table of Contents
Introduction
Agate
Alexandrite
Almandine
Amber
Amethyst
Aquamarine
Bloodstone
Carnelian
Cat’s-Eye
Black Chalcedony
Chalcedony
Citrine
Coral
Demantoid
Emerald
Hematite
Hessonite
Iolite
Ivory
Jade (Jadeite)
Jade (Nephrite)
Kunzite
Lapis Lazuli
Malachite
Malaya Garnet
Moonstone
Morganite
Onyx and Sardonyx
1
2
4
6
8
10
12
14
16
18
20
22
26
28
32
34
38
40
42
44
46
50
54
56
58
60
62
64
66
Opal
Pearl and Cultured Pearl
Peridot
Pyrope
Rhodolite
Rose Quartz
Ruby
Sapphire
Shell
Smoky Quartz
Spessartine
Spinel
Star Ruby
Star Sapphire
Tanzanite
Tiger’s-eye
Topaz
Tortoise Shell
Tourmaline
Tsavorite
Turquoise
Zircon
68
72
76
78
80
82
84
88
92
96
98
100
102
106
110
112
114
118
120
124
126
130
Introduction
For centuries, artists and poets have used images of colored stones to express love, passion, and
power. People in every era and from all walks of life have adorned themselves with the dramatic, radiant grace of colored stone jewelry.
This volume, The Essential Colored Stone Reference Guide, is written in lively, understandable
language, with stunning illustrations and an easy, look-it-up format.
Convenient organization makes it easy to put this guide to work for you. Entries are listed
alphabetically by common name. Applicable species, variety, and group names are listed below
the heading. You can refer to the Table of Contents if you want to go directly to a specific listing.
Each entry provides clear, practical information that you can use to enrich your sales
presentations. For example, a “Care and Cleaning” chart lists common cleaning methods and
the relative safety of each method for that particular gem. Common synthetics, treatments, and
imitations are listed as appropriate, too.
Another feature of each entry is the list of alternative gems at the end of each section. This
will be useful to you when, for example, you’re talking with a customer who loves purple, but
isn’t sure she wants an amethyst.
Besides practical information, some gem entries include interesting lore. For example, did
you know that amber is sometimes called “Gold of the North,” or that emerald was one of
Cleopatra’s favorite gems? There’s also a list of the places considered sources of each gem.
These bits of information can enhance your presentation and make the gem more interesting to
your customer.
The Essential Colored Stone Reference Guide covers gems you’re likely to see in jewelry
stores, catalogs, and other retail settings. It is your key to the product knowledge you need to sell
color with style and confidence. When new colored stone jewelry appears in your inventory,
look it up in the guide. You’ll find that with its beautiful photographs and friendly format, it’s
a powerful sales tool.
©1999 by GIA. All rights reserved.
1
Agate
Agate/Chalcedony
Carved agate
Agate is a fine-grained chalcedony quartz and one of the first gem materials known. Its history goes all the way back to the ancient Egyptians, who
first used it for adornment more than 3,000 years ago. Ancient cultures used
it in amulets and talismans. They believed that it provided the wearer with
a bold heart and pleasant dreams. Roman artisans carved seals from it.
Nineteenth century Victorians used it to create beautiful cameos.
The characteristic that sets agate apart from other chalcedonies is its appearance: It boasts dramatic curved or angular stripes, or bands of color. These distinctive markings vary widely in color and translucence. The patterns in some
agates look like moss, ferns, and trees—even entire landscapes. Others have
simple striped patterns of two or more colors. Besides cameos, modern cutting
styles that make the most of agate’s unique appearance
include cabochons, beads, and carvings.
Fire agate is a relative newcomer to the agate family,
discovered in the 1940s. Its mineral layers cause light
interference and give it a shimmering iridescence
against its brown bodycolor.
Sources
Brazil
India
Madagascar
Mexico
United States
Uruguay
Hardness & Toughness
Hardness
Toughness
2
61/2 to 7 on Mohs scale
Good
Varieties
Eye agate, orbicular agate
Landscape agate
Fire agate
Dendritic agate, scenic agate
Iris agate
Banded in concentric rings
Chalcedony with colored patterns resembling a landscape
Iridescent inner layers
Colorless or white, translucent,
with markings resembling trees,
ferns, moss, or landscapes
Semitransparent to translucent,
with iridescent colors
Stability
Environmental Factor
Reaction
Heat
Color may change
Chemicals
Attacked by hydrofluoric acid;
nitric acid may attack dye
Light
Treatments
Stable
Treatment
Description
Purpose
Heating
Produces
orange or
orangy red
color in yellow
to brown agate
Improves color
Dyeing
Gray South
Improves color,
American agate is improves banddyed with inoring
ganic dye. Layers
absorb dye differently depending
on porosity.
Care and Cleaning
Type of Cleaning
Advisability
Ultrasonic cleaning
Not recommended
Steam cleaning
Warm, soapy water
Landscape agate
Not recommended
Stability
Prevalence
Permanent
Common
Generally stable
Common
under normal conditions. May fade
or be removed by
chemicals.
Iris agate
Landscape agate
Safe
3
Alexandrite
Alexandrite/Chrysoberyl
Alexandrite is a rare chrysoberyl variety with chameleon-like qualities. Its
color is a lovely green in daylight or fluorescent light, but it changes to brownish or purplish red in the incandescent light from a lamp or candle flame.
Alexandrite’s dramatic color change is sometimes described as “emerald
by day, ruby by night.” Other gems also change color in response to a
change in light source, but this gem’s transformation is so striking that the
phenomenon itself is often called “the alexandrite effect.”
Abundant alexandrite deposits were first discovered in 1830, in Russia’s
Ural Mountains. Those first alexandrites were of very fine quality, and displayed vivid hues and dramatic color changes. The gem
was named after the young Czar Alexander II, and it
caught the country’s attention because its red and green
colors mirrored the Imperial Russian flag.
The spectacular Ural Mountain deposits didn’t last
forever, and now most alexandrite comes from Sri
Lanka, East Africa, and Brazil. The newer deposits contain some fine-quality stones, but many possess less
precise color change and muddier hues than the nineteenth century Russian alexandrites. You’ll still find
some of the famed Ural Mountain alexandrites in estate
jewelry. They remain the quality standard for this phenomenal gemstone.
Because of its scarcity, especially in larger sizes,
alexandrite is a relatively expensive member of the
chrysoberyl family. It shares its designation as a June
birthstone with cultured pearl and moonstone.
Sources
Brazil
East Africa
Russia
Sri Lanka
4
Hardness & Toughness
Hardness
Toughness
Stability
81/2 on Mohs scale
Excellent
Environmental Factor
Reaction
Heat
Stable
Chemicals
None
Light
Care and Cleaning
Type of Cleaning
Stable
Advisability
Ultrasonic cleaning
Usually safe
Warm, soapy water
Safe
Steam cleaning
Imitations
Alexandrites in incandescent light
Usually safe
Alexandrites in fluorescent light
Synthetic color-change sapphire
Synthetic color-change spinel
Synthetics
Flux
Czochralski
Alternatives
Color-change garnet
Color-change sapphire
5
Almandine
Almandine/Garnet
Almandine is probably one of the most familiar of the
closely related species that make up the garnet group.
It’s a fairly common red garnet, with a color range from
orangy red through red to reddish purple.
Almandine was named for Alabanda, an ancient
Asian town and an active gemstone trading and fashioning center. Ancient Romans often fashioned almandine
garnets as thin, hollowed cabochons to bring out the
intensity of their color.
Other species in the garnet group come in a variety of
hues, from browns and oranges to vibrant greens. As far
back as 3100 BC, Egyptians along the Nile worked garnet into beads and inlays. Noah is said to have recognized garnet’s inner fire and used it as a lamp on the
bow of the ark. Garnets of all species, including almandine, are considered January birthstones.
Sources
Brazil
India
Madagascar
Pakistan
Sri Lanka
United States
6
Hardness & Toughness
Hardness
Toughness
Stability
7 to 71/2 on Mohs scale
Fair to good
Environmental Factor
Heat
Light
Chemicals
Care and Cleaning
Reaction
Abrupt temperature changes likely
to cause fracturing
Stable
None, except concentrated
hydrofluoric acid
Type of Cleaning
Advisability
Steam cleaning
Never
Ultrasonic cleaning
Warm, soapy water
Imitations
Usually safe
Safe
Garnet-and-glass doublet
Alternatives
Hessonite garnet
Malaya garnet
Pyrope garnet
Rhodolite garnet
Ruby
Spessartine garnet
Spinel
Tourmaline
7
Amber
Amber belongs to the category of organic gems—the products of living
organisms and biological processes. Amber formed millions of years ago,
when sap from ancient trees hardened and fossilized. Stone Age people discovered these golden jewels along the shores of the Baltic Sea, and they
became perhaps the earliest and most consistently popular ornamental gems.
Scientists and collectors treasure amber that contains suspended animal or
plant fragments: Fossilized bits of once-living things that were trapped in the
hardening amber millions of years ago, creating a fascinating time capsule.
Some types of amber are found in the ground. Other types have been
freed and carried by tides and end up on beaches or near-shore areas. The
Baltic coast bordering Germany, Poland, and Russia is
still a source of amber, which is sometimes called “gold
of the North.” Amber’s warm luster is featured in beads,
carvings, pendants, and cabochon rings, as well as decorative items like cups, bowls, snuff boxes, and umbrella
handles.
Amber’s colors range from whites, yellows, and
oranges to reds and browns. Clear material is preferred
in the US, cloudy in Europe and North Africa. Heating
cloudy amber in oil clarifies it. Heat treatment can also
produce disk-like stress fractures and create an attractive product called sun-spangled amber.
Sources
Dominican
Republic
Germany
Mexico
Poland
Russia
8
Currently the major source
Hardness & Toughness
Hardness
Toughness
Stability
2 to 21/2 on Mohs scale
Poor
Environmental Factor
Reaction
Heat
Burns at low temperatures
Chemicals
Attacked by acids, caustics, alcohol,
gasoline
Light
Treatments
May darken with age
Treatment
Purpose
Stability
Prevalence
Amber pendant showing sun spangles
Detection
Stable
Occasional
May be detectable
Heating
Clarifies cloudy
amber
Lightens color
Stable
Occasional
Undetectable
Heating (sometimes with oil)
Produces sun
spangles
Stable
Common
May be detectable
May fade
Occasional
May be detectable
Heating in oil
Dyeing
Darkens color
Care and Cleaning
Type of Cleaning
Advisability
Ultrasonic cleaning
Never
Steam cleaning
Warm, soapy water
Imitations
Never
Safe, but hard brushes may scratch
Ambroid (reconstructed or pressed amber)
Copal (a natural resin, younger than amber)
Plastic
Yellow glass
Close-up of spider trapped in amber
Close-up of insect trapped in amber
9
Amethyst
Amethyst/Quartz
Amethyst has been the most prized member of the quartz family for centuries. Early Greek legends, and its wine-purple color, associated amethyst
with Bacchus, the god of wine. Other legends led to beliefs that amethyst
gems kept their wearers clear-headed and quick-witted in battle and in their
business affairs. It’s no wonder that fine amethyst adorns the fingers of bishops and the coronation regalia of British royalty.
Russia was once the main source of amethyst, but near the turn of the twentieth century, new deposits were discovered in South America. After that, it
became more widely available, but no less treasured. Amethyst comes in a
range of sizes, and the color selection ranges from palest lilac to rich purple.
Experts consider African amethyst’s royal purple with
reddish overtones to be the gem’s finest color.
A closely related quartz variety called ametrine contains a striking mixture of two contrasting quartzes—
purple amethyst and yellow citrine. Ametrine deposits
are found in Brazil and Bolivia.
Amethyst is the birthstone for February.
Sources
Brazil
India
Major source
Namibia
Sri Lanka
United States
Uruguay
Zambia
Hardness & Toughness
Hardness
Toughness
10
7 on Mohs scale
Good
Stability
Environmental Factor
Reaction
Heat
Abrupt temperature change may fracture stone, can alter color
Chemicals
Damaged by hydrofluoric acid, ammonium fluoride, alkalies
Light
Treatments
Treatment
Heating
Some amethyst may fade
Purpose
Lightens color
or produces
citrine or green
quartz
Care and Cleaning
Stability
Excellent
Type of Cleaning
Advisability
Ultrasonic cleaning
Usually safe
Steam cleaning
Warm, soapy water
Imitations
Prevalence
Occasional
Detection
Undetectable
Not recommended
Safe
Glass
Purple synthetic corundum
Assembled stone (synthetic spinel triplet)
Synthetics
Contemporary amethyst and
diamond pendant
Hydrothermal
Alternatives
Iolite
Rhodolite garnet
Sapphire
Spinel
Tanzanite
Topaz
Tourmaline
Carved amethyst
Ametrine
11
Aquamarine
Aquamarine/Beryl
Aquamarine’s cool blue hues are reflected in its name, which comes from
the Latin for “sea water.” Medieval sages prescribed water touched by aquamarine for a host of ills, including those affecting the eyes and lungs. They
promised the virtues of insight and foresight to the gem’s wearers.
Aquamarine crystals can grow to huge sizes, and are usually blessed with
excellent clarity. Gem bodycolors range from greenish blue to blue-green in
light tones. Usually, the color is more intense in larger stones, but some
aquamarine from Africa displays deeper blues in faceted stones of less than
5 cts. Brazil supplies the most aquamarine to the modern market.
Like emerald, aquamarine is a member of the beryl
species. The gem is March’s birthstone.
Sources
Australia
Brazil
China
Major source
Kenya
Madagascar
Mozambique
Nigeria
Pakistan
Known for intense color in smaller
sizes (under 5 cts.)
United States
Zambia
Hardness & Toughness
Hardness
Toughness
12
71/2 to 8 on Mohs scale
Good
Stability
Environmental Factor
Reaction
Heat
Exposure to heat not recommended
Chemicals
Attacked by hydrofluoric acid
Light
Treatments
Treatment
Heating
Stable
Purpose
Removes yellow, resulting
in purer blue
color
Care and Cleaning
Stability
Very good
Prevalence
Routine
A 32.10-ct. heart-shaped
aquamarine from Brazil
Detection
Undetectable
Type of Cleaning
Advisability
Steam cleaning
Usually safe, unless stone contains feathers or liquid
inclusions
Ultrasonic cleaning
Warm, soapy water
Imitations
Usually safe, unless stone contains feathers or liquid
inclusions
Safe
Glass
Synthetic spinel
Alternatives
Blue topaz
Flower brooch featuring aquamarine
Sapphire
Spinel
Tanzanite
Tourmaline
Aquamarine crystal from Afghanistan weighing over
100 cts.
13
Bloodstone
Bloodstone/Chalcedony
Bloodstone is an opaque to semitranslucent variety of
chalcedony. Its bold coloring—dark green flecked with
red—has intrigued people for centuries. The ancient
Greeks named it heliotrope (“sun-turner”) because they
observed that it flashed scarlet when they lowered it
into water and pointed it toward the sun. Many people
thought it colored water red for the same reason.
Citizens of Medieval and Renaissance Europe honored
bloodstone as a talisman that stirred passion, stopped
bleeding, and brought healing.
Rich men in the time of King Solomon prized the
gem for use in their seal rings, and it’s still set in men’s
jewelry today. Bloodstone is also popular in Christian
jewelry because its distinctive pattern reminded early
Christians of the blood of Christ at the foot of the cross.
Bloodstone is the alternate birthstone for March.
Sources
Australia
Brazil
China
India
United States
14
Hardness & Toughness
Hardness
Toughness
Stability
61/2 to 7 on Mohs scale
Good
Environmental Factor
Heat
Light
Chemicals
Reaction
Color may change
Stable
Attacked by hydrofluoric acid
Type of Cleaning
Advisability
Steam cleaning
Not recommended
Care and Cleaning
Ultrasonic cleaning
Warm, soapy water
Not recommended
Safe
15
Carnelian
Carnelian/Chalcedony
Carnelian is a semitransparent to translucent variety of chalcedony. Gem
specialists believe it was named after the kornel cherry, which grows in the
same warm shades as the gem: Yellowish orange to orangy red to brownish
orange. It’s often fashioned into beads or cameos to show off its color.
Ancient civilizations believed that carnelian transformed poor or timid
speakers into eloquent ones. Carnelian’s history began in India, where it was
mined as early as the fourth century BC.
Sources
Brazil
India
Uruguay
Hardness & Toughness
Hardness
Toughness
Stability
Good
Environmental Factor
Reaction
Light
Stable
Heat
Chemicals
16
61/2 to 7 on Mohs scale
Color may change
Attacked by hydrofluoric acid
Treatments
Treatment
Heating
Purpose
Improves color
Care and Cleaning
Stability
Stable
Type of Cleaning
Advisability
Steam cleaning
Usually safe
Ultrasonic cleaning
Warm, soapy water
Imitations
Prevalence
Common
Detection
Undetectable
Usually safe
Safe
Glass
Plastic
Alternatives
Amber
Fire opal
Jade
Sard chalcedony
Carnelian intaglio
Carnelian intaglio ring
Roman carnelian intaglio
from the first century BC
17
Cat’s-Eye
Cat’s-Eye/Chrysoberyl
This gem, with its band of reflected light across the middle, has always
reminded observers of the eye of a cat. The cat’s-eye effect, also called chatoyancy, is caused by parallel needle-like inclusions within the stone. The
gem was once known as cymophane—Greek for “waving light.” In some
cultures, its distinctive appearance made it the preferred treatment for all
sorts of eye ailments.
Chatoyancy appears in other gemstones, but fine-quality cat’s-eye
chrysoberyl sets the standard. It’s also the most valuable cat’s-eye stone. It’s
durable as well as attractive, which makes it popular in men’s rings, cufflinks,
and tie tacks. The cabochon cut brings out its cat’s-eye
effect to best advantage.
Cat’s-eye chrysoberyl ranges from brown to greenish
yellow. The finest quality specimens boast a golden
color, with bands that span the entire length of the gem.
The bands themselves are distinct, silvery-white, and
straight.
The chatoyant band in cat’s-eyes will appear to blink
when you hold the stone between two light sources,
then rotate it. As you turn the stone, the eye splits into
two bands that move apart, then back together. This
effect is called “opening and closing.”
Cat’s-eyes display another impressive effect, called
milk and honey. With the light positioned perpendicular
to the chatoyant band, the side nearest the light shows
the stone’s original bodycolor while the other side has a
milky appearance.
18
Sources
Brazil
East Africa
Sri Lanka
Hardness & Toughness
Hardness
Toughness
Stability
81/2 on Mohs scale
Excellent to good
Environmental Factor
Reaction
Heat
Stable
Chemicals
None
Light
Care and Cleaning
Stable
Type of Cleaning
Advisability
Steam cleaning
Usually safe
Ultrasonic cleaning
Warm, soapy water
Imitations
72.68-ct. cat's-eye chrysoberyl cabochon with a
317.7-ct piece of rough from Brazil
Usually safe
Safe
Cat’s-eye glass
Alternatives
Cat’s-eye quartz
Cat’s-eye tourmaline
Tiger’s-eye quartz
Cat’s-eye chrysoberyl set in art deco-style
platinum ring with diamonds
Cat’s-eye chrysoberyl mounted in art deco pin
19
Black Chalcedony
Natural black chalcedony is extremely rare. The jewelry industry commonly
calls dyed black chalcedony, which is more common, “black onyx.” This
always-stylish gem was prominent in the Art Deco jewelry of the 1920s and
1930s. Jewelry designers of the time often set it in platinum with diamonds,
or with the colorless quartz variety known as rock crystal.
Because “basic black” is always in style, so is black chalcedony. It has
the added advantages of good durability, low cost, and availability in an
almost unlimited range of sizes. It’s one of the most popular gems for beads,
cabochons, tablets, inlays, and carvings. You’ll often find this stone in men’s
jewelry.
Black chalcedony is also commonly used as a backing for opal doublets and triplets. In doublets, pieces
of opal too thin to use alone are often cemented to a
tablet of black chalcedony. This dramatizes the opal’s
play of color and gives strength to the assembled
stone. A triplet requires the addition of a protective top
made of rock crystal quartz or some other hard, colorless material.
Sources
Brazil
Gray chalcedony, later dyed black
Hardness
61/2 to 7 on Mohs scale
Hardness & Toughness
Toughness
20
Good
Stability
Environmental Factor
Heat
Light
Chemicals
Treatments
Treatment
Boiling in a
solution of sugar
and water, then
soaking in sulfuric acid. Usually
described as
“dyeing.”
Purpose
Produces black
color in gray
chalcedony
Care and Cleaning
Reaction
Color may change
Stable
Attacked by hydrofluoric acid; nitric acid may
attack dye
Stability
Stable under
normal conditions
Type of Cleaning
Advisability
Steam cleaning
Usually safe
Ultrasonic cleaning
Warm, soapy water
Imitations
Prevalence
Routine.
Virtually all
black chalcedony is dyed.
Detection
No tests.
Treatment is
assumed.
Usually safe
Safe
Glass
Plastic
Alternatives
Hematite
Jadeite jade
Nephrite jade
Onyx
21
Chalcedony
Chalcedony is one of the world’s oldest, most abundant, and most popular
gems. It was named for the ancient Turkish seaport of Chalcedon (now
called Kadikoy). Many cultures throughout history have used it for a variety of purposes. Many considered it a powerful talisman. In the third and
fourth centuries, Greek sailors wore chalcedony amulets as protection
against drowning. As late as the 1700s, many Europeans believed chalcedony would drive away ghosts and bad spirits.
Chalcedony is fairly affordable, and it comes in an incredibly wide range
of colors and patterns. These two factors make it very popular with gem and
mineral collectors. In jewelry, you’ll see it most often as beads, cabochons,
tablets, and carvings. Imaginative designers use chalcedony in some of the
most cutting-edge creations available on the market.
Mineralogists consider chalcedony a variety of quartz, but gemologists
and gem professionals treat the two as separate species. The difference
between them is that quartz occurs in large crystals, while the individual
crystals that make up chalcedony are so small that it
takes very high magnification to see them.
Sources
See Agate, Bloodstone, Carnelian, and Onyx and
Sardonyx for sources of those gems.
Australia
Brazil
Many varieties
Germany
Jasper
Czech Republic
Iceland
India
Italy
Mexico
Russia
Scotland
United States
Uruguay
22
Chrysoprase
Chrysoprase
Milky chalcedony
Chrysoprase, milky chalcedony
Jasper
Chrysocolla-in-chalcedony
Jasper, milky chalcedony
Jasper
Amethystine chalcedony, chrysocolla-in-chalcedony, chrysoprase,
jasper, milky chalcedony
Sard
Hardness & Toughness
Hardness
Toughness
Varieties
61/2 to 7 on Mohs scale
Good
Variety Name
Appearance and Comments
Amethystine chalcedony
Semitranslucent to opaque purple. Often marketed as
“purple agate” or under the trade name “damsonite.”
Agate
Bloodstone
Carnelian
Chrysocolla-in-chalcedony
Chrysoprase
Dendritic agate
Fire agate
Iris agate
Jasper
Translucent to opaque, with curved or angular color
banding; also patterns such as “moss” and “landscape.” For additional information, see Agate.
Semitranslucent to opaque, dark green with red to
brownish red spots. For additional information, see
Bloodstone.
Semitransparent to translucent, yellow-orange to
orangy red, often slightly brownish. For additional
information, see Carnelian.
Translucent to semitranslucent, intense light blue or
blue-green. Can resemble fine turquoise. One of the
most valuable chalcedony varieties.
Semitransparent to translucent,
light to medium yellowish green.
The name comes from Greek
words meaning “golden apple,”
and is ethically used only for natural-color (not dyed) material.
Chalcedony with dark inclusions
resembling tree branches.
Semitranslucent to opaque, with
iridescent colors against a brown
bodycolor.
Semitransparent to translucent, with
iridescent colors (phenomenon best
seen on thin slices in transmitted
light)
Opaque; any color or combination
of colors except solid black or
material known by another name
(agate, black chalcedony, carnelian,
and so forth). Opaque whitish
jasper is often dyed blue to imitate
lapis lazuli.
Chrysocolla-in-chalcedony
23
Milky chalcedony
Onyx
Sard
Sardonyx
Stability
Environmental Factor
Heat
Light
Chemicals
Chrysoprase chalcedony
24
Semitransparent to translucent, nearly colorless to
white or light gray. Often sold as an alternative for
moonstone.
Translucent to opaque, with straight, parallel bands of
different colors. For additional information, see Onyx
and Sardonyx.
Semitransparent to translucent, dark brown, brownish
orange, or brownish red (darker and less saturated
color than carnelian).
Onyx with sard colors alternating with either white or
black. For additional information, see Onyx and
Sardonyx.
Reaction
Color may change, especially if dyed
Stable
Attacked by hydrofluoric acid; nitric acid may attack
dye in treated material
Treatments
Treatment
Dyeing
Purpose
Produces a
wide variety of
colors
Stability
Generally stable under normal conditions
Prevalence
Common
Detection
Some colors
detectable by a
trained gemologist
or gemological
laboratory.* Often
assumed because
of unnatural color.
* If there is any doubt, send the gem to a gemological laboratory for verification. Even then,
some colors are not detectable.
Care and Cleaning
Type of Cleaning
Advisability
Steam cleaning
Usually safe
Ultrasonic cleaning
Warm, soapy water
Imitations
Usually safe
Safe
Glass
Plastic
Alternatives
Amber
Hematite
Jadeite jade
Lapis lazuli
Malachite
Moonstone
Nephrite jade
Rose quartz
Shell
Tiger’s-eye
Turquoise
Dendritic chalcedony
25
Citrine
Citrine/Quartz
Citrine is one of the US birthstones for November (the other is topaz). It’s a
quartz variety, and the top-selling transparent gem in the yellow to orange
color range. Its name was derived from the Latin word citrus, meaning
“citron” (a fruit closely related to the lemon). This gem combines a warm,
attractive color with good wearability and a moderate price—an unbeatable
combination for many customers.
Citrine comes in an exceptionally wide range of sizes. The largest transparent faceted gem on record (in terms of dimensions and volume) is a citrine.
It measures 25.5 cm × 14.1 cm × 10.0 cm (9.9 in. × 5.5 in. × 3.9 in.), and
weighs 19,548 cts. (3.9 kg/8.6 lb.). Jewelry-sized citrines are readily available
in weights of up to 20 cts. and more.
Most citrine is faceted in traditional rounds and fancy shapes, but you’ll
also find it fashioned into more unusual cuts and carvings. Leading jewelry
designers use citrine alone, in combination with diamonds, and in multicolored creations alongside gems with contrasting colors—
amethyst, aquamarine, blue topaz, and others.
Before the development of modern gemology, citrine
was traditionally confused with topaz because of their
similar colors.
Sources
Bolivia
Brazil
Spain
Hardness & Toughness
Hardness
Toughness
26
7 on Mohs scale
Good
Stability
Environmental Factor
Heat
Light
Treatment
Heating
High heat can cause color loss; sudden or extreme
temperature change can cause fracturing
Stable
Chemicals
Treatments
Reaction
Soluble in hydrofluoric acid and ammonium fluoride;
very slightly soluble in alkalis
Purpose
Produces color—
changes
amethyst to citrine
Care and Cleaning
Stability
Permanent under
normal conditions
Type of Cleaning
Advisability
Steam cleaning
Not recommended
Ultrasonic cleaning
Warm, soapy water
Imitations
Prevalence
Routine. Most
citrine is produced by heat
treating
amethyst.
6.20-ct. citrine from Brazil
Detection
Undetectable.
Treatment is
assumed.
Usually safe
Carved citrine
Safe
Glass
Plastic
Synthetic hydrothermal quartz
Synthetic sapphire
Synthetic spinel
Citrine Quartz from Brazil
Alternatives
Amber
Carnelian
Chrysoberyl
Malaya garnet
Sapphire
Smoky quartz
Spessartine garnet
Topaz
Tourmaline
27
Coral
For thousands of years, cultures around the world have
prized coral as a gem and credited this product of the sea
with magical powers. First century Romans used it to
ward off evil and to impart wisdom. It’s still worn in
modern-day Italy as protection against the “evil eye”
and as a cure for sterility.
There are two basic types of gem coral. One type
comes in a variety of lighter shades: White, cream or
pink, various shades of red or orange, and occasionally
blue, purple, or light grayish violet (known as “lavender” in the trade). The other coral type is black, dark
brown, or sometimes light brownish yellow (often
called “golden”).
All coral is composed of the remains of skeleton-like
support structures that were built by colonies of tiny
marine animals. These coral polyps, as they’re called, are
close relatives of the more familiar coral reef builders.
Coral jewelry, in the form of beads, cabochons, and
especially small carvings and cameos, has been popular
in Europe since Roman times. Its popularity is strong in
both North and South America. At one time, Asian
countries used coral more often for large carvings, but
Western influences prompted increased production and
popularity of coral jewelry in the twentieth century.
World demand for coral jewelry remains high, even
though a number of factors have combined to drastically
reduce the supply of new material in recent decades.
These factors include pollution, over-harvesting, and
increasing national and international environmental protection efforts.
For centuries, the most prized qualities of coral came
from the Mediterranean Sea, along the coasts of
Algeria, France, Italy, Morocco, Spain, and Tunisia.
28
Unfortunately, pollution and depletion have devastated these
waters. Australia—another once-important source—now prohibits the export of all native coral. The state of Hawaii protects black “King’s” coral as an endangered species. All
these factors limit modern supplies of coral, but the availability of high-quality older pieces guarantee it a permanent place in the antique market.
Sources
Japan
Malaysia
Philippines
Hardness & Toughness
Hardness
Toughness
Stability
3 to 4 on Mohs scale
Fair to good
Environmental Factor
Heat
Light
Chemicals
Chimera bracelet bangle by Cartier (not signed) of
carved coral set with diamonds in platinum
Reaction
Blackens or burns if exposed to the
flame of a jeweler’s torch
Generally stable; dyed material
may eventually fade
Easily attacked by acids and other
chemicals
Red coral
29
Treatments
Treatment
Purpose
Stability
Impregnation
with epoxy
resin or gluelike sustances
Fills and hides
cavities and
fractures
Bleaching in
hydrogen peroxide solution
Produces
“golden” color
in black coral
Stable under
normal conditions, but can
be damaged or
destroyed by
high heat and
solvents
Dyeing
Deepens or
changes color,
usually to pink
or red, but any
color is possible
Prevalence
Detection
Common in
low-quality
material
Detectable by a
trained gemologist or gemological laboratory
Common
Detectable by a
trained gemologist or gemological laboratory
Dye can be
affected or
removed by
solvents, and
can fade under
prolonged
exposure to
strong light
Occasional
Stable
Might be
detectable by a
trained gemologist or gemological laboratory*
* If there is any doubt, send the gem to a gemological laboratory for verification.
30
Care and Cleaning
Type of Cleaning
Advisability
Steam cleaning
Never
Ultrasonic cleaning
Warm, soapy water
Imitations
Risky
Safe
Glass
Plastic
Alternatives
Amber
Carnelian
Chalcedony
Cultured pearl
Carved and rough coral
Jadeite jade
Nephrite jade
Rose quartz
Shell
Enamel and coral beads torsade necklace
Different types and colors of coral
31
Demantoid
Demantoid/Andradite/Garnet
Demantoid means “diamond-like” in Dutch, the language of Renaissance
diamond cutters. Its name reflects the fact that, while demantoid is much
softer than diamond, its dispersion is higher, so its flashes of rainbow color
are very noticeable, especially in lighter-colored stones. This lush green
gem is a variety of andradite and a member of the garnet group.
Demantoid displays intense color in the green to yellow-green range.
Under the microscope, fine demantoid has another telltale signature: Its
classic “horse-tails.” They are wisps of long, golden, fiber-like inclusions
that radiate from a central point.
Demantoid was discovered in Russia’s gem-rich Ural
Mountains in 1868. Tiffany and Company’s chief gem
buyer, George Kunz, fell in love with the newly discovered gem, and the company bought up all that they
could get. Tiffany marketed it as an appealing emerald
alternative. Even though it was rarely available in sizes
larger than 2 cts., demantoid adorned much Victorian
jewelry crafted between 1895 and 1915.
The historic Russian source doesn’t yield much
demantoid any more. In fact, the scarcity of fine-quality demantoid has made it a prized collector’s stone.
Recent discoveries in Namibia, however, have
increased the availability.
Demantoid joins the rest of the garnet group as a
January birthstone.
Sources
Namibia
Russia
Zaire
32
Hardness & Toughness
Hardness
Toughness
Stability
61/2 to 7 on Mohs scale
Fair to good
Environmental Factor
Heat
Light
Chemicals
Care and Cleaning
Type of Cleaning
Ultrasonic cleaning
Steam cleaning
Warm, soapy water
Imitations
Reaction
Abrupt temperature changes likely
to cause fracturing
Close-up of the horsetail inclusion in a demantoid
Stable
Attacked by hydrofluoric acid
Advisability
Usually safe, risky if it contains
liquid inclusions
Never
Safe
Visible horsetail inclusion in a demantoid garnet
Colored CZ
Colored YAG
Garnet-and-glass doublet
Alternatives
Emerald
Green sapphire
Green zircon
Peridot
Tourmaline
Tsavorite garnet
33
Emerald
Emerald/Beryl
Emerald’s lush green has soothed souls and excited imaginations since
antiquity. Its name comes from the ancient Greek word for green, “smaragdus.” Rome’s Pliny the Elder described emerald in his Natural History, published in the first century AD: “…nothing greens greener” was his verdict.
He described the use of emerald by early lapidaries, who “have no better
method of restoring their eyes than by looking at the emerald, its soft, green
color comforting and removing their weariness and lassitude.” Even today,
the color green is known to relieve stress and eye strain.
The first known emerald mines were in Egypt, dating from at least 330
BC into the 1700s. Cleopatra was known to have a passion for emerald, and used it in her royal adornments.
Emeralds from what is now Colombia were part of
the plunder when sixteenth-century Spanish explorers
invaded the New World. The Indians had already been
using emeralds in their jewelry and religious ceremonies for 500 years. The Spanish, who treasured gold
and silver far more than gems, traded emeralds for precious metals. Their trades opened the eyes of European
and Asian royalty to emerald’s majesty.
Emerald is often mined and sold under peril—the
natural resource Colombians cherish is also coveted by
underworld drug traders. The availability of fine-quality
emerald is limited, and emerald was plagued in the late
1990s by negative publicity about treatments commonly
used to improve its clarity.
Emerald is the most famous member of the beryl
family. Legends gave it the power to make its wearer
more intelligent and quick-witted. It was once also
believed to cure diseases like cholera and malaria. Its
color reflects new spring growth, which makes it the
perfect choice of a birthstone for the month of May. It’s
also the gemstone for twentieth and thirty-fifth wedding
anniversaries.
34
Sources
Afghanistan
Brazil
Colombia
Pakistan
Russia
Zambia
Zimbabwe
One of the largest commercial producers: Fine
Colombian emeralds are highly regarded for their
excellent color
A major commercial source: Zambian emeralds tend to
have good clarity
The Sandawana Valley is a famous source
Hardness & Toughness
Hardness
Toughness
Stability
71/2 to 8 on Mohs scale
Poor to good
Environmental Factor
Heat
Light
Chemicals
Reaction
May cause fractures
Fracture fillings may dry out or
alter under intense light
Fracture fillings may be affected
by any type of chemical, emerald
itself is resistant to all acids except
hydrofluoric
Emerald cross recovered from Nuestra
Senora de Atocha Galleon
35
Treatments
Treatment
Description
Purpose
Improves clarity, improves
color
Not permanent
Routine
Dyeing
Adding colorant to the oils
or resins used
in the fracturefilling process
Improves emerald color, gives
light-colored
beryls an emerald green color
Not permanent
Rare
Coating
Covering a
light-colored
beryl with a
green plastic
Creates an
emerald imitation
Not permanent
Rare
Fracture Filling
Filling surfacereaching fractures with colorless oils or
resins. Simply
called “oiling”
in the trade
when colorless
oils are used.
Stability
Care and Cleaning
Most emeralds have been fracture-filled. An emerald’s appearance may change over time due to the
instability of its filling material. Depending upon
their condition, emeralds may be retreated by an
experienced professional.
Type of Cleaning
Advisability
Ultrasonic cleaning
Never
Steam cleaning
Warm, soapy water
36
Never
Usually safe. Avoid vigorous scrubbing
Prevalence
Imitations
Green glass
Synthetic spinel triplet
Synthetics
Flux
Hydrothermal
Alternatives
Alexandrite
Demantoid garnet
Diopside
Jadeite
Peridot
Sapphire
Tourmaline
Tsavorite garnet
Zircon
Colombian rough and cut emeralds
37
Hematite
Hematite’s shiny metallic luster and dark gray to black color give it a special beauty and appeal that’s shared by few other stones. It’s inexpensive,
and available in a wide range of sizes, so it’s a traditional favorite for men’s
rings—especially when it’s engraved with a warrior’s head or animal motif.
It’s also widely used for pendants as well as bead necklaces and bracelets.
Hematite has the highest density (weight-to-size ratio) of any commonly
available natural gem. This gives hematite jewelry a weighty feel and an
aura of value. Its high density has a down side for some wearers of hematite
earrings, though: Large pendant and hoop styles are too heavy to wear comfortably for long periods.
Hematite is composed of iron oxide, so it’s chemically the same as common rust. The name comes from
the Greek word haima, which means “blood”—referring to the red color of the mineral in its powder form.
Hematite’s name means, literally, “blood stone.”
People in ancient mideastern cultures believed that
hematite would ensure victory in lawsuits and favorable
judgments from kings and others in authority. During
Roman times, the gem was associated with Mars, god of
war: It was believed to protect a warrior who rubbed it
on his body. Native Americans also used powdered
hematite as a pigment for war paint.
Sources
England
Norway
Sweden
United States
38
Hardness & Toughness
Hardness
Toughness
Stability
51/2 to 61/2 on Mohs scale
Fair
Environmental Factor
Reaction
Heat
May become magnetic
Chemicals
Soluble in hydrochloric acid
Light
Care and Cleaning
Stable
Type of Cleaning
Advisability
Steam cleaning
Safe
Ultrasonic cleaning
Warm, soapy water
Imitations
Safe
Safe
Imitation hematite—usually made mostly of compressed
iron, and often stamped with an intaglio design. Once
marketed as “hemetine,” but that trade name was
ruled misleading by the FTC.
Alternatives
Black chalcedony
Cultured pearl
Jadeite jade
Nephrite jade
39
Hessonite
Garnet/Grossular/Hessonite
Hessonite is a variety of grossular garnet. Its close relative,
tsavorite, is also a grossular variety. But hessonite’s
warm brownish yellows, brownish oranges, and brownish
reds make quite a contrast to tsavorite’s cool green.
Because of hessonite’s color, as well as its historic connection with the spice-producing country of Sri Lanka,
this garnet is also known as “cinnamon stone.”
Sources
Brazil
Canada
Madagascar
Mexico
Sri Lanka
Tanzania
US
Hardness & Toughness
Hardness
Toughness
40
7 to 71/2 on Mohs scale
Fair to good
Stability
Environmental Factor
Heat
Light
Chemicals
Care and Cleaning
Reaction
Abrupt temperature change likely
to cause fracturing
Stable
Attacked by hydrofluoric acid
Type of Cleaning
Advisability
Steam cleaning
Never
Ultrasonic cleaning
Warm, soapy water
Alternatives
Usually safe, unless liquid
inclusions are present
Safe
Almandine
Citrine
Fire opal
Sapphire
Spessartine
Topaz
Zircon
41
Iolite
Iolite gets its name from the Greek word for violet, and
like that flower, its cool shades range from light to dark
blue and violet. It’s a transparent to translucent gem
that’s strongly pleochroic. This means that it shows different colors from different viewing angles. From some
angles, blue iolite can actually appear colorless. Other
pleochroic colors include gray, violet, or yellow. This
optical property allows the gem to act as a strong lightpolarizing filter, a feature that Viking navigators found
useful. To locate the sun—and chart their position—on
overcast days, they viewed the sky through a thin piece
of iolite.
Sources
Brazil
India
Madagascar
Namibia
Norway
Sri Lanka
Tanzania
42
Hardness & Toughness
Hardness
Toughness
Stability
7 to 71/2 on Mohs scale
Fair
Environmental Factor
Reaction
Heat
Can be damaged
Chemicals
Attacked by acids
Light
Care and Cleaning
Stable
Type of Cleaning
Advisability
Steam cleaning
Risky
Ultrasonic cleaning
Warm, soapy water
Imitations
Risky
Safe
Glass
Alternatives
Blue topaz
Sapphire
Tanzanite
43
Ivory
Ivory is an organic material that has been part of human art and culture for
thousands of years. It has always symbolized the strength, life force, and
majesty of nature, and ivory objects served ceremonial, ornamental, and
utilitarian purposes for most of the great civilizations. In Europe, archaeologists unearthed ivory carvings and artifacts that are as much as 30,000
years old. The Egyptians were crafting exquisite ivory ornaments by 8000
BC. Its easy workability and color palette—ranging from soft or radiant
whites to warm light or golden brownish yellows—made ivory a prized
medium for artisans, gem carvers, and jewelry designers.
Today, ivory is one of the world’s most controversial gem materials. It
comes from the tusks or teeth of certain mammals, and those mammals must
die in order to yield their treasure. The most familiar ivory source is the elephant. Others include the hippopotamus, narwhal, sperm whale, walrus, and
warthog. Most are endangered species.
International prohibitions exist (under the UN
Convention on the International Trade in Endangered
Species of Wild Flora and Fauna [CITES]) against trade
in ivory. More than 100 nations are parties to CITES,
and most of them have enacted laws to reinforce the
ban. Beyond this, environmental and animal-rights
activists militantly oppose commerce in ivory, and most
consumers shun it as well. Despite all this, there’s still a
strong market for ivory, which is now supplied almost
exclusively by criminal means.
A limited alternative to ivory is fossil ivory, which
comes mostly from the remains of woolly mammoths
that inhabited the northern hemisphere more than
10,000 years ago. Its main source is the Russian
Siberian region. There’s also a legitimate collector’s
market in antique ivory. Unfortunately, some dishonest
traders use treatments to artificially “age” new ivory,
thus avoiding the legal prohibitions.
Hardness & Toughness
Hardness
Toughness
44
2 1/4 to 2 3/4 on Mohs scale
Fair
Stability
Environmental Factor
Heat
Light
Causes shrinkage, cracking, and
discoloration
Yellows with age
Chemicals
Treatments
Reaction
Attacked by many chemicals; softened by nitric and phosphoric acid
Treatment
Purpose
Stable
Common
Undetectable
Dyeing
Can impart any
Stable
color, but usually
done to simulate
the appearance of
antique ivory
Common
Usually
undetectable
unless the color
is unnatural in
appearance
Stable
Darkens the
color to simulate
the appearance of
antique ivory
Undetermined
Usually
undetectable
Bleaching
Heating
Lightens or
removes stains
Care and Cleaning
Stability
Type of Cleaning
Advisability
Steam cleaning
Never
Ultrasonic cleaning
Warm, soapy water
Imitations
Prevalence
Ivory doctor’s doll
Detection
Never
Safe
Glass
Plastic
Alternatives
Chalcedony
Cultured pearl
Jadeite jade
Nephrite jade
Shell
45
Jade [Jadeite]
There are two different gem minerals that are correctly called jade, and
jadeite is one of them. (The other is nephrite.) Jadeite comes in a wide range
of attractive colors: Many shades of green, yellow, and reddish orange, plus
white, gray, black, brown and lavender (which often refers to light purple or
light grayish violet). The coloration is often streaked or mottled, giving
jadeite gemstones an interesting visual texture that carvers can use to create
imaginative and intriguing effects.
The finest quality jadeite—almost transparent with a vibrant emeraldgreen color—is known as “Imperial jade.” The royal court of China once
had a standing order for all available material of this
kind, and it’s one of the world’s most expensive gems.
Other highly valued jade varieties include “kingfisher
jade,” with a green color that’s only slightly less vivid
than Imperial; “apple jade,” which is an intense yellowish green; and “moss-in-snow jade,” which is translucent white with bright green veining, patches, or spots.
The most outstanding examples of these are almost
always bought and sold in the Asian market.
The Maya and the Aztecs prized jadeite from Central
America. They used it for medicinal purposes as well as
for jewelry, ornaments, and religious artifacts. The
name jade comes from the Spanish expression piedra de
ijada—literally “stone of the pain in the side.” Early
Spanish explorers named it after they saw natives holding pieces of the stone to their sides to cure or relieve
various aches and pains.
It was in China—where the gem-carving tradition
was already thousands of years old—that jadeite
reached its peak as an important artistic medium. The
first jadeite reached China from Burma (now known as
Myanmar) in the late 1700s, and late eighteenth and
46
early nineteenth century carvers created masterpieces that are still unsurpassed in concept, design, and technical execution.
Jadeite is a favorite medium for lapidary artists around the world. This is
especially true in China, where jade carving is still a national art form. It’s
a popular material for beads, cabochons, bangle bracelets, and small carvings. Because of its exceptional strength and toughness, it’s one of the few
gems that can be used to make hololiths—bracelets or rings carved entirely
from a single piece of stone, with no supporting metalwork or mounting.
Jadeite symbolizes prosperity, success, and good luck. It’s one of the topselling gems in Asia, but its versatile beauty and cultural associations have also
earned it an important place in the global gem and jewelry market.
Various colors of jadeite.
Sources
Guatemala
Myanmar
(Burma)
Russia
Major source of finest quality
material
United States
Hardness & Toughness
Hardness
Toughness
Stability
61/2 to 7 on Mohs scale
Exceptional
Environmental Factor
Heat
Light
Chemicals
Reaction
Damaged by a jeweler’s torch
Stable
Slightly affected by warm acids
Lavender jadeite
47
Treatments
Treatment
Dyeing
(Referred to as
“C jade”)
Purpose
To add color
(usually green or
lavender) in
white or lightcolored material
Stability
Prevalence
Detection
Fair to good.
May fade with
time
Common
Detectable by a
trained gemologist
or gemological
laboratory*
Impregnation
with paraffin
wax
Hides fractures
and improves
polish appearance
Fair. Heat will
destroy the
treatment
Common
Detectable by a
trained gemologist
or gemological
laboratory*
Bleaching and
impregnation
with plastic-type
polymer resin.
(A two-step process.) (Referred
to as “B jade”)
Improves color;
fills and hides
fractures and
cavities;
improves polish appearance
Stable under
normal conditions. High heat
can damage or
destroy the
polymer
Common
Sometimes
detectable by a
trained gemologist.
Definite proof
usually requires
advanced testing
by a gemological
laboratory*
Heating
Produces
brown or reddish color in
some material
Stable
Unknown
Undetectable
* If there is any doubt, send the gem to a gemological laboratory for verification.
Jadeite and diamond brooch.
48
Care and Cleaning
Type of Cleaning
Advisability
Steam cleaning
Safe except for wax-impregnated
material
Ultrasonic cleaning
Warm, soapy water
Imitations
Safe except for wax-impregnated
material
Safe
Glass
Plastic
Synthetics
Synthetic jadeite has been produced
on a limited basis. Identification
requires advanced testing. (If there is
any doubt, send the gem to a gemological laboratory for verification.)
Alternatives
Agate
Amber
Black chalcedony
Jadeite carving
Bloodstone
Carnelian
Chrysoprase chalcedony
Malachite
Nephrite jade
Onyx
Rose Quartz
Shell
Turquoise
49
Jade [Nephrite]
Nephrite jade has its cultural roots in the smoke-dimmed caves and huts that
sheltered prehistoric humans. In China, Europe, and elsewhere around the
world, Stone Age workers shaped this toughest of minerals into weapons,
tools, ornaments, and ritual objects. Their carvings invoked the powers of
heaven and earth and mystic forces of life and death. The ancient relationship between this gemstone and humanity persisted into modern times
among native societies in New Zealand and parts of North America. In
China it evolved into an artistic tradition that has flourished for more than
3,000 years.
Nephrite is one of the two distinct minerals accepted
as jade in the international gem and jewelry industry.
(Jadeite is the other.) It ranges from translucent to
opaque and can be light to dark green, yellow, brown,
black, gray, or white. Its colors tend to be more muted
than jadeite’s, and they’re often mottled or streaked. Its
name comes from Latin words meaning “kidney
stone”—a reference to the medicinal use of jadeite
(with which nephrite was long confused) by Native
Americans.
Generally inexpensive, extremely wearable, and
available in all sizes, nephrite is often used in jewelry
for beads, cabochons, bangle-type bracelets, and carvings. The Chinese associate it with clarity of mind and
purity of spirit. Some of the ancient symbolic motifs
still used in modern jade carvings (both nephrite and
jadeite) include:
Bat—happiness
Butterfly—long life
Dragon—power, prosperity, and goodness
Peach—immortality
Pi (flat circular disk with a hole in the center)—heaven
50
Sources
Canada
China
New Zealand
Russia
Taiwan
United States
Hardness & Toughness
Hardness
Toughness
Stability
Environmental Factor
6 to 61/2 on Mohs scale
Exceptional (the toughest known
gem)
Reaction
Heat
Damaged by a jeweler’s torch
Chemicals
Slightly affected by warm acids
Light
Nephrite carving
Stable
51
Treatments
Treatment
Purpose
Stability
Impregnation
with paraffin
wax
Dyeing
Heating
Variable,
depending on
the type of dye
Prevalence
Occasional
Detection
Hides fractures
and improves
polish appearance
Fair. High heat
will destroy the
treatment
Common
Detectable by a
trained gemologist
or gemological
laboratory*
Lightens color of
dark green material. Also darkens or “ages”
white, yellow, or
brown material
Stable
Unknown
Undetectable
Produces or
improves color
(usually green)
in light-colored
material
Detectable by a
trained gemologist
or gemological
laboratory*
* If there is any doubt, send the gem to a gemological laboratory for verification.
Care and Cleaning
Type of Cleaning
Advisability
Steam cleaning
Safe except for wax-impregnated material
Ultrasonic cleaning
Warm, soapy water
52
Safe except for wax-impregnated material
Safe
Imitations
Glass
Plastic
Alternatives
Agate
Amber
Black chalcedony
Bloodstone
Carnelian
Chrysoprase chalcedony
Hematite
Jadeite jade
Malachite
Onyx
Rose quartz
Shell
Turquoise
53
Kunzite
Kunzite/Spodumene
George Frederick Kunz (1856-1932) was a pioneer gemologist and longtime
buyer for Tiffany and Company. He was also a world-recognized expert
on—and avid promoter of—American gemstones. In 1902, he identified a
new gem-quality variety of the mineral spodumene in San Diego County,
California. The new gem was named kunzite in his honor.
This transparent stone’s light and delicate—but often bright—“rose” pink
to bluish purple “lilac” color has endeared it to gem lovers and connoisseurs, especially in the US and Japan. The most valued kunzite colors are
the more intense pinks and bluish purples, but the lighter pinks are the most
common. Kunzite is very popular with customers looking for gems in soft pastel colors.
The supply of fine-quality kunzite is limited, but various faceted fancy shapes are usually available in sizes
as large as 50 cts. The gem has poor toughness due to
cleavage, and its attractive color can fade with exposure
to bright light. Because of these factors, kunzite is a
gem that requires special care, but many consider the
extra care worthwhile because of its beauty.
Sources
Afghanistan
Brazil
Madagascar
United States
Hardness & Toughness
Hardness
Toughness
54
61/2 to 7 on Mohs scale
Poor because of cleavage
Stability
Environmental Factor
Heat
Light
Treatment
Irradiation
High heat can cause color loss; sudden temperature
change can cause breaks
Bright light causes the color to fade
Chemicals
Treatments
Reaction
Very slowly attacked by concentrated hydrofluoric
acid
Purpose
Produces
kunzite from
colorless or
light-colored
spodumene
Care and Cleaning
Stability
Color fades in
bright light (as
does untreated
material)
Type of Cleaning
Advisability
Steam cleaning
Never
Ultrasonic cleaning
Warm, soapy water
Imitations
Prevalence
Unknown
Detection
Undetectable
Never
Safe
Glass
Synthetic sapphire
Synthetic spinel
Alternatives
Amethyst
Morganite
Rhodolite garnet
Rose quartz
Sapphire
Spinel
Topaz
Tourmaline
Necklace designed by Paloma
Picasso, featuring large kunzite
with diamonds and cultured
pearls set in 18K gold
55
Lapis Lazuli
Lapis lazuli belongs to a small category of gems called “rocks” because
it’s an aggregate of several different minerals. (A mineral is a natural inorganic material with a specific—and unique—chemical composition and
crystal structure). It’s often simply called “lapis” in the trade.
Lapis is typically opaque, and its colors are medium to dark greenish
“navy” blue, pure “royal” blue, or violetish “midnight” blue. Depending on
its source, it sometimes shows white calcite veining, which lowers its value,
or golden-looking flecks of the mineral pyrite. The pyrite spangles nestled
in the blue bodycolor—like golden stars in a summer sky—produce a
unique visual appeal.
Lapis has been mined in Afghanistan for more than 6,000 years. It was treasured by the ancient civilizations of Mesopotamia, Egypt, China, Greece, and
Rome. Its Latin name literally means “blue stone.” Lapis was considered an
emblem of chastity and a cure for sadness. It was also
thought to offer protection from evil and ensure the help
of angels.
The supply of lapis is plentiful in today’s jewelry market. Large stones are readily available, and it’s a popular
gem material for beads, cabochons, tablets, and carvings.
Afghan lapis has always been known for its fine quality
and color purity, while lapis mined in Chile often shows
less-desirable white veining.
Lapis was dropped from the official US birthstone list
in the 1950s, but for many years it was one of the gems
for December. You might suggest it as an alternative for
customers who were born in that month.
Sources
Afghanistan—Finest quality
Chile
Russia
Hardness & Toughness
Hardness
Toughness
56
5 to 6 on Mohs scale
Fair
Stability
Environmental Factor
Heat
Light
High heat can induce an undesirable green color, or
cause complete color loss
Stable
Chemicals
Treatments
Reaction
Decomposed slowly by hydrochloric acid; discolored
by cyanide solution
Treatment
Purpose
Stability
Coating or
impregnation
with oil, paraffin, or plastic
Improves color
and polish
appearance;
also seals any
dye
Dyeing
Improves color
and hides white
veining
Fair. Some
dyes fade or
are affected by
solvents
Prevalence
Common
Detection
Fair. Treatment
(especially oil
and paraffin)
can be damaged
or destroyed
by heat and
chemicals
Common
Detectable by a
trained gemologist
or gemological
laboratory*
Detectable by a
trained gemologist
or gemological
laboratory*
* If there is any doubt, send the gem to a gemological laboratory for verification.
Care and Cleaning
Type of Cleaning
Ultrasonic cleaning
Steam cleaning
Warm, soapy water
Imitations
Advisability
Risky
Never
Safe
Glass
Plastic
Alternatives
Chalcedony
Suite of high-quality lapis lazuli from Afghanistan
Sodalite
57
Malachite
Malachite is an opaque gem with a strong bluish green to green color. It typically shows curved or circular banding (in varying shades of green) that
gives it a distinctive beauty. (A closely related gem material, azurmalachite,
combines malachite green with the dark blue of the mineral azurite in attractive bands and patterns.)
Malachite has a long history as a gem. One of its main components, and
the cause of its color, is copper. It was found along with that metal by early
civilizations as they emerged from the Stone Age. The Egyptians used malachite for jewelry and other ornamental purposes as early as 4000 Bc. In the
Middle Ages (from about 500 to 1500 AD) people in Europe often hung
malachite on cradles to assure peaceful sleep for their children and protect
them from witchcraft. People wore pieces with eyeshaped markings as amulets to ward off the “evil eye.”
Modern jewelry uses for malachite include beads,
cabochons, tablets, inlays, and carvings. Its high density
gives malachite jewelry such as bead necklaces a weighty
feeling that enhances customers’ sense of its value.
Because malachite is relatively soft, has poor toughness,
and can be attacked by many chemicals, it’s considered an
extra-care gem. With proper handling, however, malachite
can provide years of pleasure for its wearer.
Sources
Australia
Russia
United States
Zaire
Hardness & Toughness
Hardness
Toughness
58
31/2 to 4 on Mohs scale
Poor
Stability
Environmental Factor
Heat
Light
Chemicals
Reaction
High heat can cause discoloration and damage
Stable
Attacked by acids
Treatment
Stability
Treatments
Impregnation
with paraffin or
epoxy resin
Purpose
Intensifies
color, improves
polish appearance, and hides
small cracks
Fair. Treatment
can be damaged
or destroyed
by heat and
chemicals
Prevalence
Unknown
Detection
Detectable by a
trained gemologist
or gemological
laboratory*
* If there is any doubt, send the gem to a gemological laboratory for verification.
Care and Cleaning
Type of Cleaning
Advisability
Steam cleaning
Never
Ultrasonic cleaning
Warm, soapy water
Imitations
Never
Safe
Glass
Plastic
Synthetics
Suite of malachite
Synthetic malachite has been produced on a limited basis. Identification requires
advanced testing. (If there is any doubt, send the gem to a gemological
laboratory for verification.)
Alternatives
Agate (dyed green)
Jadeite jade
Nephrite jade
Turquoise
59
Malaya Garnet
Malaya (also spelled malaia) garnet is a relatively new
member of the garnet group. Specimens of it first
appeared in the 1960s, mixed in with parcels of rhodolite garnets from the Umba River Valley of East Africa.
At first, buyers rejected the unfamiliar gem material, so
local miners and dealers gave it a Swahili name that
literally translates “out of the family.”
Tests eventually proved malaya garnet to be a chemical mixture of two garnets: pyrope and spessartine. The
gem’s lively color—light to dark pinkish, reddish, or
yellowish orange—conquered buyer resistance, and
during the 1980s it gained a small but strong market,
particularly in the US.
Malaya is one of the more expensive garnets. It’s
usually available in various fancy shapes up to about 10
cts. Along with the other garnets, it’s a US birthstone for
January. In Europe, malaya is known as umbalite, after
the region that remains the gem’s only source.
Sources
Kenya
Tanzania
Hardness & Toughness
Hardness
Toughness
60
7 to 71/2 on Mohs scale
Fair to good
Stability
Environmental Factor
Heat
Light
Chemicals
Care and Cleaning
Reaction
Sudden temperature change can
cause fracturing
Stable
Slightly attacked by hydrofluoric
acid
Type of Cleaning
Advisability
Steam cleaning
Never
Ultrasonic cleaning
Warm, soapy water
Imitations
Usually safe
Color-change 8.51-ct.
malaya garnet under
fluorescent light
Color-change 8.51-ct.
malaya garnet under
incandescent light
Safe
Glass
Synthetic sapphire
Synthetic spinel
Alternatives
Almandine
Carnelian
Citrine
Sapphire
Spessartine garnet
Spinel
Color-change malaya garnets in fluorescent light
Topaz
Tourmaline
Zircon
Color-change malaya garnets in incandescent light
61
Moonstone
Moonstone/Orthoclase/Feldspar
Faceted moonstone with blue
adularescence
According to Hindu mythology, moonstone is made of
solidified moonbeams. Many other cultures also associate this gem with moonlight, and it’s easy to see why. Its
internal structure scatters the light that hits it and creates
a phenomenon known as adularescence. The visual
effect is reminiscent of the full moon shining through a
veil of high, thin clouds.
Legends say that moonstone brings good luck. Many
believed that you could see the future if you held a
moonstone in your mouth during a full moon.
Moonstone ranges from semitransparent to opaque.
You’ll most often find it in cabochons and carvings, set
in rings and pendants. It’s also popular in bead necklaces and bracelets. It’s usually colorless, white, or light
bluish gray, with white or blue adularescence. Other
colors include light green, yellow, brown, and sometimes gray to black. The market supply is normally
steady in sizes up to about 25 cts., with larger stones
available in limited quantities. Along with alexandrite
and cultured pearl, moonstone is one of the US birthstones for June.
Sources
India
Myanmar (Burma)
Sri Lanka
Hardness & Toughness
Hardness
Toughness
62
6 to 61/2 on Mohs scale
Poor because of cleavage
Stability
Environmental Factor
Heat
Light
Chemicals
Care and Cleaning
Reaction
High heat or sudden temperature
change can cause breaks
Stable
Attacked by hydrofluoric acid
Type of Cleaning
Advisability
Steam cleaning
Never
Ultrasonic cleaning
Warm, soapy water
Imitations
Never
Carved moonstone and diamond pendant
Safe
Glass
Plastic
Alternatives
Milky chalcedony
63
Morganite
Morganite/Beryl
In 1911, a transparent gem discovered on the African island of Madagascar
was hailed as an exciting new alternative to kunzite and pink tourmaline.
The rose pink to lilac gem was named in honor of wealthy banker and gem
connoisseur John Pierpont Morgan. Morgan was an avid customer of
Tiffany’s, and the jewelry store enthusiastically promoted the gem.
Eventually, Madagascar’s morganite deposits declined and Brazil
became the gem’s top producer. Although the gem’s finest color is a deep
magenta, most morganites on the market are a pale pink. Many Brazilian
morganites emerge from the mines sporting an attractive peach (orangepink) hue that’s appealing to some buyers. But producers usually heat treat gems of this hue to arrive at a pink
shade that’s preferred in the marketplace.
Morganite is a variety of beryl, which makes it a relative of emerald and aquamarine. The gem’s beauty and
limited availability make it a favorite of collectors.
Sources
Afghanistan
Brazil
Madagascar
US
Hardness & Toughness
Hardness
Toughness
64
71/2 to 8 on Mohs scale
Good
Stability
Environmental Factor
Heat
Light
Chemicals
Treatments
Treatment
Heating
Purpose
Improves pink
color by
removing
orange tint
Care and Cleaning
Reaction
Pinkish orange may fade to pink;
may fracture if liquid inclusions
present
Stable
Resistant to all acids except
hydrofluoric
Stability
Stable, except
at temperatures
over 400°C
Prevalence
Unknown
Type of Cleaning
Advisability
Steam cleaning
Risky if highly included (rare)
Ultrasonic cleaning
Warm, soapy water
Alternatives
Detection
Undetectable
Risky if highly included (rare)
Safe
Kunzite
Pink tourmaline
Rose quartz
Sapphire
Spinel
Topaz
65
Onyx and Sardonyx
Onyx/Chalcedony and Sardonyx/Chalcedony
Onyx and sardonyx are both chalcedony varieties characterized by straight, parallel bands of different colors.
In onyx, the bands are usually black and white. In sardonyx, dark brown, brownish orange, or brownish red
alternate with either white or black.
Since Greek and Roman times, both varieties have
provided gem carvers with ideal materials for cameos
and intaglios. The color banding allows the creation of
carved designs that contrast dramatically with their
backgrounds.
Inexpensive, plentiful, and available in large sizes,
onyx and sardonyx are also traditionally popular for
beads, cabochons, and tablets. In Europe, sardonyx
once symbolized the humility of the saints and the
virtue of spiritual living.
Sardonyx is accepted as one of the US birthstones for
August. (The other is peridot.)
Sources
Brazil
Madagascar
United States
Uruguay
Hardness & Toughness
Hardness
Toughness
66
61/2 to 7 on Mohs scale
Good
Stability
Environmental factor
Reaction
Light
Stable
Heat
Chemicals
Care and Cleaning
Color may change
Attacked by hydrofluoric acid
Type of Cleaning
Advisability
Steam cleaning
Usually safe
Ultrasonic cleaning
Warm, soapy water
Imitations
Usually safe
Safe
Sardonyx cameo
Glass
Plastic
Alternatives
Agate
Carnelian
Jadeite jade
Nephrite jade
Shell
Black and white onyx cameo set in gold and
surrounded by pearls
67
Opal
Opal is the world’s most popular phenomenal gem. Many cultures have credited opal with supernatural origins and powers. Arabic legends say it falls from
the heavens in flashes of lightning. The ancient Greeks believed opals gave
their owners the gift of prophecy and guarded them from disease. Europeans
have long considered the gem a symbol of hope, purity, and truth.
Opal is one of the US birthstones for October (along with tourmaline).
Some people think it’s unlucky for anyone born in another month to wear
an opal. But that particular superstition comes from a novel written in the
1800s (Anne of Geierstein by Sir Walter Scott) and not from ancient belief
or experience. In fact, throughout most of history, opal has been regarded
as the luckiest and most magical of all gems because it
can show all colors. Once, it was thought to have the
power to preserve the life and color of blond hair.
Although experts divide gem opals into many different
categories, four of the main types are:
• White opal—translucent to semitranslucent with
play-of-color against a white or light gray bodycolor
• Black opal—translucent to opaque with play-ofcolor against a black or other dark bodycolor
• Fire opal—transparent to translucent with brown,
yellow, orange, or red bodycolor. This material—
which often doesn’t show play-of-color—is also
known as “Mexican opal,” “gold opal,” or “sun opal”
• Boulder opal—translucent to opaque with play-ofcolor against a light to dark background. Host-rock
fragments, or matrix, are part of the finished gem
The market supply of fine black opal is extremely
limited, but white and fire opals are generally available in a wide range of sizes. You’ll usually see black
or white opals fashioned as cabochons and set in rings,
pendants, pins, or earrings. Fire opals are used in the
same kinds of jewelry, but they’re often faceted. All
three types occasionally appear as beads and carvings.
68
Pieces of white or black opal that are too thin to use alone often become part of opal doublets
or triplets. In these assembled stones, a sliver of opal is cemented—usually with black adhesive
that dramatizes the play-of-color—to a backing such as chalcedony, glass, or plastic. A doublet
consists of two pieces (the opal and the backing), while a triplet also has a protective top made
of rock crystal quartz or colorless glass.
Explaining Play-of-color
Play-of-color occurs because opal is made up of sub-microscopic spheres stacked in a grid-like
pattern—like layers of Ping-Pong balls in a box. This structure breaks up light into spectral colors.
The colors you see depend on the sizes of the spheres. Those approximately 0.1 micron (one tenmillionth of a meter) in diameter produce violet. Spheres about 0.2 microns in size produce red.
Those in between produce intermediate hues.
Common trade terms for play-of-color patterns include:
• Pinfire or pinpoint—small, close-set patches of color
• Harlequin or mosaic—broad, angular, close-set patches of color
• Flame—sweeping reddish bands or streaks that shoot across the stone
• Peacock—mainly blue and green
Sources
Australia
Black and white opal
Mexico
Fire opal
Brazil
White opal
Blue opal pendant set in platinum with diamonds
Hardness & Toughness
Hardness
Toughness
5 to 61/2 on Mohs scale
Very poor to fair
Fire opal
69
Stability
Environmental Factor
Heat
Light
Reaction
High heat or sudden temperature change can cause
fracturing
Generally stable, but heat from intense light can cause
fracturing (known as “crazing”)
Chemicals
Attacked by hydrofluoric acid and caustic alkalis
Warn buyers that loss of moisture, and crazing, can result from storage in airtight containers
such as safe deposit boxes.
Treatments
Treatment
Purpose
Stability
Prevalence
Detection
Soaking in dye,
silver nitrate, or
sugar and acid
(known as “sugar
treatment”)
Creates or
improves playof-color and
simulates the
appearance of
black opal
Poor to good
Common
Detectable by a
trained gemologist
or gemological
laboratory*
Fair to poor.
Common
Treatment is shallow, and abrades
or chips away
easily
Detectable by a
trained gemologist
or gemological
laboratory*
Impregnation
with oil, wax, or
plastic
Improves play-of- Fair to poor for
Common
color and prevents oil or wax; excelor disguises
lent for plastic
fracturing. Black
plastic also creates
the appearance of
black opal
Smoke impregna- Creates or
tion
improves playof-color and
simulates the
appearance of
black opal
Oil and wax
treatments are
detectable by a
trained gemologist
or gemological
laboratory. Advanced
laboratory testing is
almost always
required for plastic*
* If there is any doubt, send the gem to a gemological laboratory for verification.
70
Care and Cleaning
Type of Cleaning
Advisability
Steam cleaning
Never
Ultrasonic cleaning
Warm, soapy water
Imitations
Never
Safe
Glass
Plastic
Synthetics
Available in a variety of colors
Alternatives
No gem duplicates opal’s unique combination of color and phenomenon. As
alternatives, you might suggest stones with similar bodycolors, or those that
show other special optical effects.
Fire agate
Iris agate
71
Pearl and Cultured Pearl
Perhaps the best-loved gems of all time, pearls—and their modern counterparts, cultured pearls—occur in a wide variety of colors. The most familiar
colors are white and cream (light yellowish brown). Black, gray, and silver
are also relatively common, but the palette of pearl colors extends to every
hue. The bodycolor is often modified by additional colors called overtones,
which are typically pink (called rosé), green, purple, or blue. And some
pearls show the iridescent phenomenon known as orient.
Pearls are treasures from the Earth’s streams, rivers, lakes, seas, and
oceans, and they’ve always embodied the mystery, power, and life-sustaining
nature of water. The spherical shape of some pearls also led many cultures
to associate this gem with the moon. In ancient China, pearls were believed
to guarantee protection from fire and fire-breathing dragons. In Europe, they
symbolized modesty, chastity, and purity.
Cultured pearls are popular for bead necklaces and bracelets, or mounted in
solitaires, pairs, or clusters for use in earrings, rings, and pendants. Larger
pearls with unusual shapes are favorites with creative jewelry designers.
Pearl—cultured or natural—is a US birthstone for June,
together with alexandrite and moonstone.
Natural and Cultured Pearls
Natural pearls are organic gems that form in the bodies of
certain mollusks, usually around a microscopic irritant and
always without human help of any kind. They’re composed mostly of concentric layers of nacre, which is made
of the same basic material as mother-of-pearl—the inside
layer of certain shells. Natural pearls were once more
prevalent around the world—and prized by almost all
cultures. They virtually disappeared from the mainstream
jewelry market in the twentieth century due to pollution,
over-fishing, and economic factors. Now normally available only through antique or estate dealers and auctions,
fine natural pearls can command very high prices.
The growth of cultured pearls requires human intervention and care. The mollusks themselves are raised
specifically for culturing. To begin the process, skilled
technicians insert one or more nuclei (usually shell beads
or pieces of flesh from other mollusks) into each mollusk.
These nuclei act as irritants and trigger the secretion of
nacre. Workers tend the mollusks until the cultured pearls
are harvested. This usually happens about 18 months, but
72
occasionally up to 3 years, after nucleation. Besides human intervention,
another big difference between natural and many cultured pearls is that the bead
nucleus accounts for most of the volume and weight of the cultured product.
The first steps toward pearl culturing occurred hundreds of years ago in
China, and Japanese pioneers successfully produced whole cultured pearls
around the beginning of the twentieth century. These became commercially
important in the 1920s (about the same time natural pearl production began
to drop). From the 1930s through the 1980s, pearl culturing diversified and
spread to various countries around the world.
A trained gemologist can often identify cultured pearls—particularly in
strands, necklaces, or bracelets—with a reasonably high degree of certainty.
Positive identification of natural pearls requires advanced laboratory testing. If
there is any doubt, send the gem to a gemological laboratory for verification.
FTC Guides on Pearls
The US FTC Guides include several sections dealing with representations concerning natural, cultured, and imitation pearls. Some of the most important
points are:
A pair of earrings with 2.22-ct. t.w. hot reddish pink
spinels, spessartine garnets, and cultured pearl drops
• It’s unfair or deceptive to use the term “pearl” alone or the term “natural”
(or anything similar) for cultured pearls or imitations
• It’s unfair or deceptive to use terms such as “cultured,” “synthetic,” or
anything similar for imitation pearls
• It’s unfair or deceptive to use the term “Oriental pearl” for anything
other than natural pearls from the Persian Gulf
• It’s unfair or deceptive to use geographic terms like “South Sea” for
cultured pearls from other sources
• It’s unfair or deceptive to use the term “pearl” or “cultured pearl” for
specimens of inferior appearance or quality
Cultured Pearl Types and Related Products
• Akoya—the type of cultured pearl most familiar to many jewelry customers. The typical size range is 6 mm to 8 mm, but you might see akoya
cultured pearls as small as 2 mm or as large as 11 mm. Most have a white
to cream bodycolor. Other natural colors include yellow, gray, and blue.
Japan and China both produce saltwater akoya cultured pearls.
• South Sea—Australia, Indonesia, and the Philippines are leading sources
of these saltwater cultured pearls. Myanmar (Burma) and Thailand are
also important producers. South Sea cultured pearls usually range from
about 8 mm to 18 mm in size. The most common bodycolors are white,
cream, and golden (dark brownish yellow), but you’ll see them in other
colors, too.
• Tahitian—Cultivated primarily around the islands of French Polynesia
(the most familiar of which is Tahiti), these saltwater cultured pearls
usually range from white to black. Other colors include dark metallic
73
greens and purples. The usual size is about 8 mm to 17 mm, although larger pearls exist in
limited quantities.
• Freshwater—Pearls cultured in streams, rivers, and lakes. They’re produced in a wide range
of sizes, shapes, and colors. China and the US are the leading sources.
• Keshi (Japanese for “poppyseed”)—Pearls that form (without being intentionally nucleated)
in mollusks undergoing pearl cultivation.
• Blister pearls—Cultured or natural pearls that form over a solid core inside a freshwater or
saltwater mollusk’s shell. The side that faces the shell is flat and lacks nacre.
• Mabé—An assembled product consisting of a cultured blister pearl dome cemented to a
backing made from mother-of-pearl shell. After harvesting, the nucleus is removed and the
hollow interior is usually filled with a material such as epoxy resin.
Hardness & Toughness
Hardness
Toughness
Stability
21/2 to 4 on Mohs scale (very soft and easily scratched or abraded)
Usually good, but variable due to aging, dehydration, and sometimes
excessive bleaching during initial processing
Environmental Factor
Heat
Light
Chemicals
Reaction
High heat can burn cultured pearls or cause discoloration, splitting, or cracking
Generally stable, but heat from intense light can cause
dehydration and nacre cracking
Attacked by many chemicals and all acids; hair spray,
perfume, cosmetics, and even acid perspiration can
damage nacre
Harry Winston black cultured pearl and diamond
cufflinks
74
Treatments
Treatment
Purpose
Lightens dark
spots
Stable
Dyeing
Imparts or
changes bodycolor
Usually stable,
but some colors
may fade
Irradiation
Produces black,
Stable
gray, or blue-gray
color in white or
cream-colored
pearls
Bleaching
Stability
Prevalence
Detection
Common
Detectable by a
trained gemologist
or gemological
laboratory*
Routine for most Undetectable,
types of light
but assumed
bodycolor
cultured pearls;
usually considered
a step in standard
processing rather
than a treatment
Occasional
Sometimes detectable
by a trained gemologist,
but often requires
advanced testing by a
gemological laboratory*
* If there is any doubt, send the gem to a gemological laboratory for verification.
Care and Cleaning
Type of Cleaning
Advisability
Steam cleaning
Never
Ultrasonic cleaning
Warm, soapy water
Never
Safe for occasional, thorough cleaning (if strung, be sure the string is
completely dry before wearing)
For routine care, advise customers to wipe cultured pearls with a very soft,
clean cloth after each wearing.
Imitations
Glass
Plastic
Alternatives
Black chalcedony
Coral
Hematite
Shell—mother-of-pearl
Cultured black Tahitian pearls, 13-15.6-mm, 18K gold,
with diamonds (31 pearls)
75
Peridot
Peridot has always been associated with light. The Egyptians called it the
“gem of the sun.” Some believed that it protected its owner from “terrors of
the night,” especially when it was set in gold. Others strung the gem on donkey hair and tied it around the left arm to ward off evil spirits. Today,
Arizona’s San Carlos Indian Reservation is the world’s most commercially
important producer.
Peridot is usually transparent. It comes in an attractive range of colors,
from brownish or yellowish green to greenish yellow. Customers will be
attracted to the bright lime greens and more subdued olive greens of this
lovely gem.
This gem is relatively inexpensive and plentiful, and
normally available in standard shapes and calibrated
sizes up to about 5 cts. Larger stones are also fairly easy
to find. Tumbled and faceted peridot is used for bead
necklaces and bracelets, often combined with gems in
contrasting colors—amethyst, citrine, and pink tourmaline, to name a few.
The word peridot comes from the Arabic faridat, which
means “gem.” Most peridot formed deep inside the Earth
and was brought to the surface by volcanoes. Some has
also come to Earth in meteorites, but this extraterrestrial
peridot is extremely rare, and you’re not likely to see it in
a retail jewelry store. Mineralogists refer to the stone as
olivine.
Peridot is one of the US birthstones for August (sardonyx is the other).
Sources
Myanmar (Burma)
Pakistan
United States
76
Hardness & Toughness
Hardness
Toughness
Stability
61/2 to 7 on Mohs scale
Fair to good
Environmental Factor
Heat
Light
Chemicals
Care and Cleaning
Reaction
Rapid or uneven heat can cause
fracturing
Stable
Attacked easily by sulfuric acid,
and less easily by hydrochloric
acid; can be attacked over a long
period of time by acid perspiration
Type of Cleaning
Advisability
Steam cleaning
Never
Ultrasonic cleaning
Warm, soapy water
Imitations
Topaz and peridot brooch with pearls set in yellow gold
Risky
Safe
Glass
Plastic
Synthetic sapphire
Synthetic spinel
Alternatives
Chrysoberyl
Demantoid garnet
Emerald
Jadeite jade
Sapphire
Topaz
Tourmaline
Tsavorite garnet
Zircon
77
Pyrope
Pyrope/Garnet
Pyrope is a mineral that’s part of the garnet group. The
Greek word pyropos translates as “fiery-eyed,” and it’s
easy to see how the gem got its name: The finest
pyrope garnets have a glowing red color. Other pyrope
colors range from medium to dark reddish orange to
purplish red.
Pyrope was popular with the Greeks and Romans. It
was prominent in jewelry of the Victorian era (18371901), but it’s now in short supply and seldom available
in sizes much larger than 2 cts. Collectors of antique
jewelry prize the elaborate Victorian jewelry set with
multitudes of small pyropes.
Like other garnets, pyrope is a US birthstone for
January. It’s occasionally called “Bohemian garnet,”
after the region (now part of the Czech Republic) that
was once an important source.
Sources
South Africa
United States
Hardness & Toughness
Hardness
Toughness
78
7 to 71/2 on Mohs scale
Fair to good
Stability
Environmental Factor
Heat
Light
Chemicals
Care and Cleaning
Reaction
Damaged by the heat of a jeweler’s
torch; sudden temperature change
can cause fracturing
Stable
Slightly attacked by hydrofluoric
acid
Type of Cleaning
Advisability
Steam cleaning
Risky
Ultrasonic cleaning
Warm, soapy water
Imitations
Usually safe
Pyrope (from Bohemia) bracelet
Safe
Glass
Synthetic ruby
Alternatives
Almandine garnet
Rhodolite garnet
Ruby
Spinel
Topaz
Tourmaline
Zircon
79
Rhodolite
Rhodolite/Garnet
Rhodolite’s name is a modern composite of the Greek
words rhodon, “rose,” and lithos, “stone.” It’s a member of the garnet group, a mixture of almandine and
pyrope. Technically, gemologists classify garnets by a
combination of color and various tests, but to most
dealers and other gem professionals, any predominantly purple garnet is rhodolite. Rhodolite’s full color
range includes light to dark purplish red through reddish purple.
Rhodolite’s attractive color has made it one of the
most valuable of the gems generally classified as “red”
garnets. It’s also the best-selling garnet besides almandine, and enjoys a strong market supply and availability
in a wide range of sizes. Like other garnets, rhodolite is
a US birthstone for January.
Sources
Sri Lanka
Tanzania
Zimbabwe
Hardness & Toughness
Hardness
Toughness
80
7 to 71/2 on Mohs scale
Fair to good
Stability
Environmental Factor
Heat
Light
Chemicals
Care and Cleaning
Reaction
Sudden temperature change can
cause fracturing
Stable
Slowly attacked by hydrofluoric
acid
Type of Cleaning
Advisability
Steam cleaning
Never
Ultrasonic cleaning
Warm, soapy water
Imitations
Usually safe
Safe
Fantasy cut rhodolite garnet (9mm x 21mm x 7mm)
by Bart Curren set as pendant in 14K yellow gold
Glass
Synthetic ruby
Alternatives
Almandine garnet
Pyrope garnet
Ruby
Spinel
Topaz
Tourmaline
Zircon
Pink rhodolite garnet, rose octagon cut, 2.34 ct., from
East Africa
81
Rose Quartz
Rose Quartz/Quartz
Rose quartz is a lovely quartz variety that typically ranges in color from
very light to medium dark pink. Often, it has numerous internal fractures
that give it a cloudy translucence and a visual texture that’s almost like
the veining in jadeite jade. Internal reflections sometimes give rose
quartz specimens in the semitransparent range an intriguing “floating
light” effect.
Sometimes, a multitude of tiny inclusions provides the stone with a star
effect. A cabochon cut combined with coating or mirror-like foil on the back
enhances the star.
Rose quartz is generally inexpensive. You’ll see the
best color in the medium to large sizes: Small stones
with good color can be harder to find. Its attractive color
and good durability make this gem a great choice for
bead necklaces and bracelets.
Clean, close-to-transparent material might be
faceted, while cabochon cuts are popular for stones set
individually in metal mountings. Carvings from larger
pieces make beautiful pendants.
Sources
Brazil
India
Madagascar
Sri Lanka
Hardness & Toughness
Hardness
Toughness
82
7 on Mohs scale
Good
Stability
Environmental Factor
Heat
Light
Chemicals
Care and Cleaning
Reaction
High heat can cause change or loss
of color; sudden temperature
change can cause fracturing
Sometimes fades with prolonged
exposure to bright light
Soluble in hydrofluoric acid and
ammonium fluoride; very slightly
soluble in alkalis
Type of Cleaning
Advisability
Steam cleaning
Risky
Ultrasonic cleaning
Warm, soapy water
Imitations
Usually safe
Safe
Glass
Plastic
Alternatives
Agate
Kunzite
Sapphire
Spinel
Star sapphire
Topaz
Tourmaline
Star rose quartz
83
Ruby
Ruby/Corundum
15.97-ct. Burma ruby
Ruby has accumulated a host of legends over the centuries. In Sanskrit (the
ancient sacred language of India), one of the terms for ruby is ratnaraj,
“King of Gems.” People in India believed that rubies enabled their owners
to live in peace with their enemies. In Burma (a ruby source since at least
600 AD—now called Myanmar), warriors wore rubies to make themselves
invincible in battle.
Many medieval Europeans wore rubies to guarantee health, wealth, wisdom, and success in love. As the US birthstone for July, and the world’s
best-known and best-loved red gem, ruby still captivates the hearts and
imaginations of gem professionals and consumers alike.
Large, fine-quality rubies are extremely rare and
valuable. But strong worldwide production and an array
of treatments have increased availability and put rubies
within the reach of most customers.
Common cutting styles for ruby include mixed-cut
ovals or antique cushions for transparent material, and
cabochons or beads for translucent to opaque stones.
Corundum has excellent toughness, and it’s harder than
any other natural gem except diamond. This makes it
ideal for rings as well as many other types of jewelry.
The name ruby comes from the Latin word ruber,
which means “red.” The most expensive ruby color is a
deep, pure, vivid red. Stones a little pinkish, purplish, or
orangy red are also considered rubies, but gem and jewelry professionals make careful distinctions between
ruby and pink, purple, or orange sapphire. (Ruby and
sapphire are both corundum varieties.)
Generally, the difference depends on a combination
of hue, tone, and saturation, but market culture and
geography also make a difference. Gems that would be
considered pink or purple sapphire in the US are often
classified and sold as rubies in some Asian countries.
It’s important to keep such regional trade practice variations in mind if you work in different markets, or with
an international clientele.
84
Sources
Afghanistan
Kenya
Madagascar
Myanmar
(Burma)
Considered to produce finest quality
rubies
Sri Lanka
Often lighter in tone than rubies
from Myanmar or Thailand
Tanzania
Thailand
Mine production declined in
the 1990s, but it’s still the
world center for treatment and
wholesale trade
Vietnam
Hardness & Toughness
Hardness
Toughness
Stability
9 on Mohs scale
Usually excellent, but stones with certain treatments or large fractures or inclusions can be less
durable
Environmental Factor
Heat
Light
Chemicals
Burmese ruby and diamond choker
Reaction
High heat can cause a change in color or clarity; it can
also damage or destroy fracture- and cavity-fillings
Generally stable, but heat from bright lights can cause
oil to leak or dry out
Can harm fillings and remove oil; soldering flux
containing boron, and firecoat made with boric acid
powder, will etch the surface of even untreated stones
85
Treatments
Treatment
Purpose
Stability
Lattice diffusion
(heating to very
high temperature
in the presence of
a coloring agent)
Creates red color
in corundum
Detectable by a
trained gemologist
or gemological
laboratory*
Fracture-filling
with oil or epoxy
resin
Improves clarity
appearance by
hiding fractures.
Colored oil or
resin also
improves color
appearance
Fairly common
Stable under
normal conditions,
but the red color
might be removed
in some stones if
they’re repolished
or recut
Occasional
Fair. Heat and
chemicals can
damage or destroy
the filling. Oil
will probably dry
out or discolor in
time
Detectable by a
trained gemologist
or gemological
laboratory*
Cavity-filling
with epoxy
resin or glass
Improves clarity
appearance by
hiding cavities;
adds weight if the
cavities are large
Fair. Heat and
Common
chemicals can
damage or
destroy the filling
Detectable by a
trained gemologist
or gemological
laboratory*
Heat
Improves color
and/or clarity
appearance
Stable unless
the stone is
heated to very
high temperatures
Prevalence
Very common;
experts estimate that up to
95 percent of
stones undergo
some sort of
heat treatment
Detection
May be detectable
by a trained gemologist or gemological
laboratory.* Can be
undetectable, but
assumed because of
prevalence
* If there is any doubt, send the gem to a gemological laboratory for verification.
1.02-ct. Burmese ruby
86
Care and Cleaning
Type of Cleaning
Advisability
Steam cleaning
Usually safe, but never for fractureor cavity-filled stones
Ultrasonic cleaning
Warm, soapy water
Imitations
Usually safe, but never for fractureor cavity-filled stones
Safe, but avoid strong detergents
and vigorous scrubbing on oiled
stones
Glass
Synthetics
Czochralski
Flame fusion
Floating zone
Ruby and diamond bracelet
and necklace set
Flux
Hydrothermal
Alternatives
Almandine garnet
Pyrope garnet
Rhodolite garnet
Spinel
Topaz
Tourmaline
Vietnamese rubies from Luc Yen and Quy Chau set in
jewelry (.33 - 1.94-ct)
87
Sapphire
Sapphire/Corundum
For centuries, sapphire has been associated with royalty and romance. The association was
reinforced in 1981, when Britain’s Prince Charles gave a blue sapphire engagement ring to Lady
Diana Spencer. Until her death in 1997, Princess Di, as she was known, charmed and captivated
the world. Her sapphire ring helped link modern events with history and fairy tales.
In ancient Greece and Rome, kings and queens were convinced that blue sapphires protected
their owners from envy and harm. During the Middle Ages, the clergy wore sapphires to symbolize Heaven, and ordinary folks thought the gem attracted heavenly blessings. In other times
and places, people instilled sapphires with the power to guard chastity, make peace between
enemies, influence spirits, and reveal the secrets of oracles.
In folklore, history, art, and consumer awareness, sapphire has always been associated with
the color blue. Its name comes from the Greek word sappheiros, which probably referred to
lapis lazuli. Most jewelry customers think all sapphires are blue, and when gem and jewelry
professionals use the word “sapphire” alone, they normally mean “blue sapphire.”
In the trade, “blue sapphire” refers to stones ranging from very light to very dark greenish or
violetish blue, as well as those in various shades of pure blue. Large, top-quality stones are rare,
but blue sapphires in other sizes and grades are almost always available.
Not all sapphires are blue, however. It’s a variety of the same species as ruby—corundum—
and any corundum that doesn’t qualify as ruby is
considered sapphire. Fancy sapphires, as they’re called,
come in violet, green, yellow, orange, pink, purple, and
intermediate hues. There are also parti-colored sapphires
that show a combination of different colors. And some
stones exhibit the phenomenon known as color change,
most often going from blue in daylight or fluorescent
lighting to purple under incandescent light. Sapphires
can even be gray, black, or brown.
Colorless sapphires were once popular diamond imitations, and in recent years they’ve staged a comeback
as accent stones. Fancy sapphires are generally less
available than blue ones, and some colors are scarce,
especially in very small or very large sizes. Still, fancy
sapphires create a rainbow of options for customers
who like the romance associated with this gem, but who
also want something out of the ordinary.
Transparent sapphires of all colors are most often
faceted. Translucent to opaque material is usually cut
into cabochons or used for beads. Corundum is very
hard and tough, and can be used in any type or style of
jewelry, and worn by just about any customer. Sapphire
is the US birthstone for September.
Special trade terms for fancy sapphires include:
• amethystine or plum sapphire—purple
88
• golden sapphire—yellow or orangy yellow
• padparadscha sapphire—pinkish orange to orange-pink with light to medium tone
and vivid saturation. The name comes from the Sinhalese term padmaragaya, or
“lotus color.” (Sinhalese is the majority language of Sri Lanka.)
• white sapphire—colorless
Sources
Australia
Blue and fancy
China
Blue and fancy
Famous historic source of fine blue sapphire, production
is now very limited.
Cambodia
India/Pakistan
(Kashmir)
Kenya
Madagascar
Myanmar
(Burma)
Blue and fancy
Blue and fancy
Blue and fancy
Blue and fancy
Nigeria
Blue
Rwanda
Fancy
Pakistan
Sri Lanka
Tanzania
Thailand
United States
Vietnam
Fancy
Blue and fancy
Blue and fancy
Blue and fancy
Blue and fancy
Blue and fancy
Padparadscha sapphire set in a ring with diamonds
and blue sapphires
Hardness & Toughness
Hardness
Toughness
Stability
9 on Mohs scale
Usually excellent, but stones with large fractures or
inclusions, or some treatments, can be less durable
Environmental Factor
Heat
Light
Chemicals
Reaction
High heat can cause change in color or clarity, and can
damage or destroy fracture and cavity fillings
Generally stable, but irradiated yellow or orange stones fade
quickly; heat from bright lights can cause oil to leak or dry
out
Can harm fillings and remove oil; soldering flux containing
boron, and firecoat made with boric acid powder, will etch
the surface of even untreated stones
89
Treatments
Treatment
Purpose
Stability
Lattice diffusion
(heating to very
high temperature
in the presence of
a coloring agent)
Creates almost
any color in
corundum
Stable under normal conditions,
but the color
might be removed
in some stones if
they’re repolished
or recut
Fracture filling
with oil or epoxy
resin
Improves clarity
appearance by
hiding fractures.
Colored oil or
resin also
improves color
appearance
Fair to good. Heat Rare for all
and chemicals can colors
damage or destroy
the filling. Oil
will probably dry
out or discolor in
time.
Heat
Cavity filling
with epoxy
resin or glass
Irradiation
Most commonly
improves color
and/or clarity
appearance
Improves clarity
appearance by
hiding cavities;
adds weight if
the cavities are
large
Produces yellow
or orange from
colorless, light
yellow, and some
very light blue
material
Stable unless the
stone is heated to
very high temperatures
Prevalence
Very common for
blue sapphires
(experts estimate
that up to 95 percent of stones
undergo some sort
of heat treatment);
common for golden sapphires
Common for
almost all colors
Detection
May be detectable
by a trained
gemologist or
gemological
laboratory.* Can
be undetectable,
but assumed
because of
prevalence
Detectable by a
trained gemologist
or gemological
laboratory*
Detectable by a
trained gemologist
or gemological
laboratory*
Fair. Heat and
chemicals can
damage or
destroy the
filling
Rare for all
colors
Detectable by a
trained gemologist
or gemological
laboratory*
Extremely
poor. Color
fades quickly
(in minutes to
days).
Rare
Detectable by
“fade test.”
(Place the stone
under bright light
for a couple of
days)
* If there is any doubt, send the gem to a gemological laboratory for verification.
90
Care and Cleaning
Type of Cleaning
Advisability
Steam cleaning
Usually safe, but never for fracture- or cavity-filled
stones
Ultrasonic cleaning
Warm, soapy water
Imitations
Usually safe, but never for fracture- or cavity-filled
stones
Safe, but avoid strong detergents and vigorous scrubbing
on oiled stones
Glass
Synthetic spinel
Synthetics
Czochralski
Flame fusion
Floating zone
Flux
Hydrothermal
Sapphire and diamond necklace
* If there is any doubt, send the gem to a gemological laboratory for verification.
Alternatives
Alexandrite
Amethyst
Aquamarine
Chrysoberyl
Citrine
Kunzite
Malaya garnet
Rhodolite garnet
Spessartine garnet
Spinel
Tanzanite
Topaz
Tourmaline
Zircon
91
Shell
Since prehistoric times, shell has been a by-product of the quest for food by
cultures living around the Earth’s rivers, lakes, seas, and oceans. Long ago,
humans began using attractive shells for jewelry. Because it’s durable and
easy to fashion, shell has remained popular as a gem material right up to the
present. Its close association with water—especially the sea—gives it an
aura of romance and magic similar to that of pearl and coral.
Ranging from translucent to opaque, shell comes in
many colors. The most common colors are white and
various shades of gray, brown, yellow, orange, and pink.
Some shell has bands or patterns of different colors.
Other material shows the iridescent effect known as
orient.
Its abundance, low cost and availability in large
pieces make shell ideal for beads, cabochons, inlays,
and carvings. Color-banded material is ideal for cameos
because it allows the creation of designs that contrast
dramatically with their backgrounds.
Some of the finest shell cameos appear in jewelry
from the mid-1800s. During those years, Queen
Victoria’s fondness for cameos created a fashion trend
that inspired skilled gem artists to produce masterpieces
of artistic and technical beauty.
Much of the shell used in today’s mainstream jewelry market—including imaginative designer pieces—
comes from the mollusks that are also used for pearl
culturing. Various species of shellfish provide material
for the jewelry sold in tourist and resort locales.
The types of shell you’re most likely to see in a retail
jewelry store include:
92
• Mother-of-pearl—the inside of the shell from a pearl-producing mollusk. The bodycolor is usually white, but it can also be brown or gray.
Mother-of-pearl’s rich luster and frequent display of orient come close
to duplicating the appearance of pearl (but only on one side of the
material).
• Abalone shell—mother-of-pearl that’s usually from the mollusk
known to scientists as haliotis. It typically has dark gray or brown
bodycolor and striking orient. Abalone from the waters around
Australia and New Zealand is often called Paua shell. Its bright blue
and green orient gives it the look of a peacock’s tail feathers.
• Conch shell—obtained from the giant queen conch. Its color usually
ranges from pale to fairly bright pink or orange. The color is often
layered or banded with white, and some shells have a pattern described
as flame-like. The queen conch also produces a material known as
conch pearl. It has an attractive porcelain-like sheen, but it lacks the
pearly coating of a true pearl. The sunrise-pink color and flame patterns
of fine specimens make them treasures for gem connoisseurs, especially
in Europe, the Middle East, and Asia.
• Helmet shell—the type most often used for cameos. It’s generally layered
in two colors: white and brown, or white
and orange.
• Ammonite—the fossilized shells
of squid-like animals that flourished about 65 million years
ago. (Their closest living
relative is the chambered
nautilus.) The shells have
a coiled shape, and specimens with iridescence
are the ones used in
jewelry, sometimes as
assembled stones with
quartz tops.
Gem-inlaid shells are used in producing such jewelry
items as cufflinks, earrings and pins
93
Sources
Australia
Abalone, mother-of-pearl
Italy
A center for shell carving
Canada
Madagascar
New Zealand
United States
West Indies
Ammonite
Helmet
Abalone
Abalone, conch, mother-of-pearl, ammonite
Conch, helmet
Hardness & Toughness
Hardness
Toughness
Stability
31/2 on Mohs scale
Fair
Environmental Factor
Heat
Light
Treatment
Dyeing
Blackens in the flame of a jeweler’s torch
Generally stable, but conch shell and some dyed material
gradually fades in sunlight
Chemicals
Treatments
Reaction
Easily attacked by acids
Purpose
Produces a variety of colors
Stability
Fair. Dyes may
fade
Prevalence
Common
Detection
Detectable by a
trained gemologist
or gemological
laboratory*
* If there is any doubt, send the gem to a gemological laboratory for verification.
Black and white shell cameo set in gold
94
Care and Cleaning
Type of Cleaning
Advisability
Steam cleaning
Risky
Ultrasonic cleaning
Warm, soapy water
Imitations
Risky
Safe
Glass
Plastic
Alternatives
Agate
Carnelian
Coral
Cultured pearl
Fire agate
Jadeite jade
Moonstone
Nephrite jade
Cameos fashioned from mother of pearl shell
Onyx
Rose quartz
Sardonyx
95
Smoky Quartz
Smoky Quartz/Quartz
Smoky quartz is one of the most common and inexpensive transparent gems
on the market. Its color varies from light to dark brown, and some stones are
so dark they’re almost black. Smoky quartz is a traditional gem in the
Scottish Highlands. There, it’s also known as cairngorm, after the
Cairngorm Mountains of Scotland, an old but now depleted source. Very
dark smoky quartz—often called morion—was popular in the somber
mourning jewelry of the late Victorian period (1861-1901).
You’ll seldom see smoky quartz in sizes under a carat, but larger stones
are always available in most standard shapes and sizes. Smoky quartz has
good durability, so it’s suitable for any type of jewelry.
Its color makes it a good choice as a gemstone accent
for warm yellow and orange wardrobe colors.
Because of its color, many consumers (and some professionals) confuse smoky quartz with topaz, but topaz
is a different gem species.
Sources
Brazil
Switzerland
United States
Hardness & Toughness
Hardness
Toughness
96
7 on Mohs scale
Good
Stability
Environmental Factor
Heat
Light
Soluble in hydrofluoric acid and ammonium
fluoride; very slightly soluble in alkalis
Treatment
Purpose
Heat
Lightens the
color of very
dark material
Irradiation
High heat can cause change or loss of color;
sudden temperature change can cause fracturing
Stable
Chemicals
Treatments
Reaction
Produces
smoky quartz
from rock crystal (colorless
quartz)
Care and Cleaning
Stability
Excellent
Prevalence
Common
Detection
Excellent
Occasional
Undetectable
(duplicates
processes that
occur naturally)
Type of Cleaning
Advisability
Steam cleaning
Risky
Ultrasonic cleaning
Warm, soapy water
Alternatives
Undetectable
(duplicates
processes that
color natural
material)
Usually safe
Safe
Chalcedony
Citrine
Moonstone
Topaz
Tourmaline
Zircon
Faceted and rough smoky quartz
8500 ct. smoky quartz
97
Spessartine
Spessartine/Garnet
Customers who think all garnets are red will be surprised and delighted with
spessartine. Some gems of this garnet species are a bright and lively orange.
Others range from medium-light to dark yellowish or reddish orange.
Market supply is sometimes limited, but rounds and fancy shapes are normally available in sizes up to 10 cts. You can usually also find larger stones
with a little searching. Prices for spessartine—especially stones from more
remote locations and those with a bright orange color—are generally a little
higher than those for red garnets like almandine and pyrope.
The gem’s name comes from Spessart, a district in
the state of Bavaria, Germany, that was once an important source. Customers born in January are among those
most likely to be interested in spessartine, because it
offers a birthstone color that’s a little different.
Sources
Brazil
Madagascar
Myanmar (Burma)
Namibia
Sri Lanka
United States
Hardness & Toughness
Hardness
Toughness
98
7 to 71/2 on Mohs scale
Fair to good
Stability
Environmental Factor
Heat
Light
Chemicals
Care and Cleaning
Reaction
Sudden temperature change can
cause fracturing
Stable
Very slowly attacked by hydrofluoric
acid
Type of Cleaning
Advisability
Steam cleaning
Never
Ultrasonic cleaning
Warm, soapy water
Imitations
Usually safe, but risky for stones
with large or numerous inclusions
or fractures
Safe
Glass
Synthetic sapphire
Alternatives
Amber
Carnelian
Citrine
Fire opal
Malaya garnet
Sapphire
Spinel
Topaz
Tourmaline
99
Spinel
Spinel is a good candidate for the title of “History’s Most UnderAppreciated Gem.” Some ancient mines that supplied gems for royal courts
from Rome to China produced spinels, but they were usually confused with
better-known stones like ruby and sapphire.
Some of the world’s most illustrious “rubies” are actually spinels. One of
these is the Black Prince’s Ruby, a polished but unfaceted red spinel that
weighs about 170 cts. It appears in historical records dating back to the
1300s, and it’s a central stone in the British Imperial State Crown.
Modern technology hasn’t helped spinel’s confused identity, either—at
least, as far as the general public is concerned. This is largely due to the
widespread use of synthetic spinel as an imitation for many other gems.
Most customers don’t even know there’s a natural version of the stone.
Limited availability also contributes to spinel’s lack of public recognition. Gem-quality material is typically transparent and faceted, but it’s hard
to find in sizes larger than 5 cts.
Spinel’s color range includes violet, blue, orange, red, pink, and purple.
Blue spinels are often grayish and subdued, but the best are a deep rich
color. The reds can rival fine ruby. And the vivid orange to orange-red stones
merit their trade name—flame spinel. Some spinels
show color-change, usually turning from grayish blue in
daylight or fluorescent light to purple under incandescent light.
In addition to its attractive colors, spinel is a hard,
tough stone that’s suitable for daily wear in any type of
jewelry. It will always be popular with customers who
like beautiful and unusual gems.
Sources
Cambodia
Myanmar
(Burma)
Sri Lanka
Known for fine-quality pink and
red spinels
Tanzania
Thailand
Hardness & Toughness
Hardness
Toughness
100
8 on Mohs scale
Good
Stability
Environmental factor
Reaction
Light
Stable
Heat
Chemicals
Care and Cleaning
High heat may cause the color to fade
Stable
Type of Cleaning
Advisability
Steam cleaning
Usually safe
Ultrasonic cleaning
Warm, soapy water
Imitations
Usually safe
Safe
Glass
Synthetic ruby
Synthetic sapphire
Red spinel from Myanmar (Burma)
Synthetics
Flame fusion
Flux
Alternatives
Almandine garnet
Amethyst
Aquamarine
Fire opal
Kunzite
Malaya garnet
Morganite
Pyrope garnet
Rhodolite garnet
Ruby
Sapphire
Spessartine garnet
Tanzanite
Topaz
Tourmaline
Blue spinel
101
Star Ruby
Star Ruby/Corundum
According to Eastern folklore, star rubies ward off evil
and bring good luck to their owners. But the market
supply of these auspicious gems is generally very limited. Fine stones are rare prizes eagerly sought by collectors and connoisseurs.
Star rubies vary from semitransparent to opaque and
from light to dark red or purple-red. They display a
phenomenon called asterism. It’s caused by tiny needle-like inclusions that reflect and scatter light within
the stone. Star ruby’s star usually has six rays, and it
requires skilled cabochon cutting to bring it out.
The finest star rubies are almost transparent, with a
strong deep color that rivals non-phenomenal rubies.
They show a sharp, complete star that glides smoothly
back and forth as you rock the stone gently.
Star rubies display their optical charms best when
they appear as center stones in elegant ballerina-style
ring settings, surrounded by flashing diamond
baguettes.
The typical size range for star rubies is 1 ct. to 10
cts., but much larger stones exist. One of the largest
fine-quality star rubies on public display is the
Smithsonian Institution’s 137-ct. Rosser Reeves Ruby.
Along with ruby, star ruby is considered a US birthstone for July.
102
Sources
India
Kenya
Myanmar (Burma)
Sri Lanka
Tanzania
Thailand
Hardness & Toughness
Hardness
Toughness
Stability
Excellent except in stones with repeated twinning or
large fractures
Environmental Factor
Heat
Light
Chemicals
Star ruby from Tanzania
9 on Mohs scale
Reaction
High heat can burn oil and change
the stone’s color or the quality of
the star effect
Generally stable, but heat from
bright lights can cause oil to leak
or dry out
Can remove oil; soldering flux
containing boron, and firecoat
made with boric acid powder, will
etch the surface of the stone
103
Treatments
Treatment
Purpose
Stability
Oiling or dyeing
Hides cracks
and improves
clarity and color
appearance
Lattice diffusion
Creates the star
effect
Fair. Can be
damaged or
destroyed by
high heat and
solvents. Oil
will probably
dry out or discolor in time.
Heating followed
by slow cooling
Creates or
improves the
star effect
Prevalence
Detection
Stable unless
the stone is
heated to very
high temperatures and then
cooled rapidly
Occasional
Undetectable
Occasional
Detectable by a
trained gemologist
or gemological
laboratory*
Stable under
normal conditions, but the
star effect can
be damaged or
destroyed if
the stone is
repolished or
recut
Rare
Detectable by a
trained gemologist
or gemological
laboratory*
* If there is any doubt, send the gem to a gemological laboratory for verification.
104
Care and Cleaning
Type of Cleaning
Advisability
Steam cleaning
Safe except for oiled stones and
those with fractures
Ultrasonic cleaning
Warm, soapy water
Imitations
Safe except for oiled stones and
those with fractures
Safe, but avoid strong detergents
and vigorous scrubbing on oiled
stones
Glass or other inexpensive material engraved with a star on the backside of
the stone, or backed with metallic foil engraved with a star design.
Synthetics
Flame fusion
Alternatives
Star almandine
Star moonstone
Star rose quartz
Star sapphire
Star spinel
105
Star Sapphire
Star Sapphire/Corundum
A cabochon-cut star sapphire characteristically shows a six-rayed star,
caused by needle-like “silk” inclusions that reflect and scatter light. Star
sapphires range from semitransparent to opaque. They come in many of
the same colors as non-phenomenal sapphires, but supplies of most colors
are limited: Green star sapphires are rare, and yellow or orange ones are
very rare.
Black star sapphire, which ranges from translucent to opaque, is often
very dark brown, green, or blue, rather than true black. It’s the most available and least expensive natural star stone, and it’s especially popular for
men’s jewelry.
Modern heat treatments that remove inclusions from
rough material have made fine-quality star sapphires
rare. Marketed gems typically range from 1 ct. to 10 cts.
in size, but you can sometimes find larger stones as
well. The American Museum of Natural History’s collection includes one of the world’s largest and most
spectacular blue star sapphires—the 153-ct. Star of
India.
Some traditions say that star sapphire is a stone of
destiny, and that its star acts as a guiding light and protects its wearer against evil. To medieval Christians, the
three intersecting bands that form the star represented
the spiritual virtues of Faith, Hope, and Charity. Today,
star sapphire provides a phenomenal September birthstone alternative.
106
Sources
Australia
Kenya
Myanmar (Burma)
Sri Lanka
Tanzania
Thailand
Hardness & Toughness
Hardness
Toughness
Stability
9 on Mohs scale
Excellent except in stones with repeated twinning or
large fractures
Environmental Factor
Heat
Light
Chemicals
Reaction
High heat can burn oil and
change the stone’s color or the
quality of the star effect
Generally stable, but heat from
bright lights can cause oil to leak
or dry out
Can remove oil; soldering flux
containing boron, and firecoat
made with boric acid powder,
will etch the surface of the stone
107
Treatments
Treatment
Purpose
Stability
Oiling or dyeing
Hides cracks
and improves
clarity and
color appearance
Lattice diffusion
Creates the star
effect
Fair. Can be
damaged or
removed by
high heat and
solvents. Oil
will probably
dry out or discolor in time.
Heating followed
by slow cooling
Creates or
improves the
star effect
Prevalence
Detection
Stable unless
the stone is
heated to very
high temperatures and then
cooled rapidly
Occasional
Undetectable
Occasional
Detectable by a
trained gemologist
or gemological
laboratory*
Stable under
normal conditions, but the
star effect can
be damaged or
destroyed if
the stone is
repolished or
recut
Rare
Detectable by a
trained gemologist
or gemological
laboratory*
* If there is any doubt, send the gem to a gemological laboratory for verification.
Care and Cleaning
Type of Cleaning
Ultrasonic cleaning
Steam cleaning
Warm, soapy water
108
Advisability
Safe except for oiled stones and those with fractures
Safe except for oiled stones and those with fractures
Safe, but avoid strong detergents and vigorous scrubbing on oiled stones
Imitations
Glass or other inexpensive material engraved with a star on the backside of
the stone, or backed with metallic foil engraved with a star design.
Synthetics
Flame fusion
Alternatives
Star moonstone
Star rose quartz
Star ruby
Star spinel
A 3,965-ct. sapphire from an area of Sri Lanka that is
known to produce star sapphires of over 500 cts.
109
Tanzanite
Tanzanite
Tanzanite is relatively new to the colored stone galaxy. This transparent blue gem first turned up
in 1962, scattered on the Earth’s surface in northern Tanzania, a country in eastern Africa.
Scientists identified it as a variety of the mineral zoisite. About five years later, a prospector discovered a large deposit of it in the same area, and serious mining began.
Tiffany & Company recognized its potential as an international seller and made a deal to
become its main distributor. Tiffany named the gem after the country it came from, and promoted it with a big publicity campaign in 1968. Almost overnight, tanzanite was popular with
leading jewelry designers and other gem professionals, as well as with customers who had an
eye for beautiful and unusual gems.
Tanzanite’s public recognition and popularity have grown steadily. But there have been wide
fluctuations in the gem’s supply and price level, due mostly to Tanzania’s volatile political, social,
and economic conditions. That country remains the gem’s only source, so the outlook for long-term
availability is also doubtful. (You can keep up with its market variability by reading industry publications, attending trade shows, and talking to suppliers.)
Tanzanites are routinely heat-treated to produce colors that include light to dark violetish blue
and bluish purple, as well as pure blue. Rich, deep hues are valued most, but you’ll usually see
these only in stones weighing 5 cts. or more. This is mainly because of decisions made during the
cutting process. Tanzanite typically shows strong pleochroism, which means it displays different
colors from different directions. It usually looks violetish
blue from some directions, purplish from others.
Predominately blue tanzanite is generally worth more
per carat, but because of the way tanzanite crystals grow,
a cutter can usually get a bigger stone by orienting the
gem to show the purple color. With small rough, size is
normally the main consideration. While the trade
considers the pure blue stones to be “top” grade, some
customers actually prefer the lighter and more purplish
colors. This means you can offer them what they like
best at an affordable price.
Tanzanite is a special-care gem for two reasons:
sensitivity to thermal shock and the potential for
cleavage. Sometimes the temperature change between
the hot lights of the display case and the chilly glass
countertop in an air-conditioned showroom can be
enough to develop cleavages in tanzanite.
Because of its susceptibility to cleavage, tanzanite
shouldn’t be handled carelessly. If you’re helping young
or active customers select tanzanite jewelry, try suggesting pieces that won’t be too exposed to accidental
bumps—pendants and earrings are good choices. For
everyday wear, it’s best to select jewelry that’s designed
to protect the stone.
110
Sources
Tanzania
Hardness & Toughness
Hardness
Toughness
Stability
6 to 7 on Mohs scale
Fair to poor, due to cleavage and sensitivity to thermal shock
Environmental Factor
Reaction
Heat
Sudden temperature change can cause cracking
Chemicals
Attacked by hydrochloric and hydrofluoric acid
Light
Treatments
Treatment
Heat
Stable
Purpose
Produces
tanzanite color
in transparent
brownish
material
Care and Cleaning
Stability
Stable
Type of Cleaning
Advisability
Steam cleaning
Never
Ultrasonic cleaning
Warm, soapy water
Imitations
Prevalence
Routine
Detection
Undetectable, but
assumed because
of prevalence
Never
Safe
Glass
Synthetic sapphire
Synthetic spinel
Synthetic spinel triplet
Alternatives
Amethyst
Iolite
Sapphire
Spinel
111
Tiger’s-Eye
Tiger’s-Eye/Quartz
Tiger’s-eye is one of the top-selling phenomenal gems. Varying from
translucent to opaque, it comes in warm earth tones that include brown,
brownish yellow, and reddish brown. Its main distinguishing characteristic
is its “eye,” called chatoyancy.
Tiger’s-eye’s chatoyancy is different from the chatoyancy in cat’s-eye
chrysoberyl. For one thing, it usually has a wavy appearance, rather than a
straight, sharp look. Also, tiger’s-eye can be cut in many ways, even flat, while
cat’s-eye has to be fashioned as a cabochon to bring out the phenomenon.
Explanation for these differences lies in their different “eye” causes: In tiger’seye, reflections of light from the fibrous structure of the gem itself create the
eye, while in cat’s-eye, the eye comes from inclusions rather than structure.
Tiger’s-eye is inexpensive and available in most standard sizes. It’s a popular material for cabochons (usually with flat backs), beads, tablets, cameos, and
intaglios. Good toughness makes tiger’s-eye a great gem
for everyday wear, and it’s a frequent choice for men’s
jewelry
Other chatoyant quartz gem varieties are scarcer and
usually more expensive. These include:
• Hawk’s-eye or falcon’s eye—grayish blue material
with chatoyancy like tiger’s-eye
• Zebra tiger’s-eye—tiger’s-eye with grayish or blue
streaks
• Cat’s-eye quartz—brownish yellow, brownish green
to greenish yellow. Shows a true cat’s-eye effect. (It
must be cut as a cabochon to show the eye.)
Sources
India
South Africa
Sri Lanka
Hardness & Toughness
Hardness
Toughness
112
7 on Mohs scale
Good
Stability
Environmental Factor
Reaction
Light
Stable
Heat
Chemicals
Treatments
Soluble in hydrofluoric acid and ammonium fluoride;
very slightly soluble in alkalis
Treatment
Purpose
Heat
Produces a
reddish brown
color
Bleaching
(sometimes followed by plastic coating)
Dyeing
Sudden temperature change can cause fracturing
Lightens the
color. Plastic
coating seals the
fibrous structure
and prevents
contamination
with dirt and
foreign matter
Adds various
color
Stability
Excellent
Prevalence
Common
Detection
Excellent
Common
Undetectable
Usually good.
Common
Some dyes may
be affected by
solvents, or fade
with prolonged
exposure to bright
light.
Undetectable, but
light brownish
yellow color is a
strong indication
of treatment
Detectable by a
trained gemologist
or gemological
laboratory*
* If there is any doubt, send the gem to a gemological laboratory for verification.
Care and Cleaning
Type of Cleaning
Advisability
Steam cleaning
Risky
Ultrasonic cleaning
Warm, soapy water
Imitations
Usually safe
Safe
Glass
Plastic
Alternatives
Cat’s-eye chrysoberyl
Cat’s-eye tourmaline
113
Topaz
Most authorities agree that the name topaz comes from Topazios, the old
Greek name for an island in the Red Sea, now called Zabargad. (The island
never produced topaz, but it was once a source of peridot, which was confused with topaz before the development of modern mineralogy.) Some
scholars trace the origin back to Sanskrit (an ancient language of India) and
the word topas or tapaz, meaning “fire.”
The ancient Greeks believed that topaz gave them strength. In Europe
during the Renaissance (the period from the 1300s to the 1600s) people
thought that topaz could break magic spells and dispel anger. For centuries,
many people in India have believed that topaz worn above the heart assures
long life, beauty, and intelligence.
Most consumers are under the impression that topaz
is an easy gem to recognize. But what they might think
of as topaz could actually be the more common citrine
and smoky quartz. This confusion shows when you’re
displaying topaz jewelry and your customer says something like “I didn’t realize topaz was so expensive” or
“Isn’t topaz brown?” You will need to clear up these
misunderstandings before you go further in your presentation.
Topaz actually has an exceptionally wide color range
that, besides brown, includes various tones and saturations of blue, green, yellow, orange, red, pink, and purple. Colorless topaz is another option. The color varieties are often identified simply by hue—blue topaz,
pink topaz, and so forth—but there are also a couple of
special trade names:
• Imperial topaz—medium reddish orange to orangered. This is one of the most expensive colors.
• Sherry topaz—yellowish brown or brownish yellow
to orange. This term comes from the color of sherry
wine. (Stones in this color range are often called
precious topaz to help distinguish them from the
less expensive citrine and smoky quartz.)
114
Strong output from sources around the world and
treatments that expand the range of usable gems guarantee
a steady supply of topaz. However, market availability
varies according to color. Blue topaz is abundant, and
there’s usually plenty of sherry topaz, but the supply of
imperial, red, purple, and pink tends to be limited.
Most colors are available in standard faceted shapes,
but the sizes differ from color to color. Blue usually
ranges from 1 ct. to 25 cts., while other colors normally
run from 1 ct. to 10 cts. You might also find some larger
stones, especially in sherry or blue.
Generally, red is the most valuable topaz color, but
market prices and preferences vary from country to
country. Imperial topaz brings highest prices in Japan
and Germany. Japanese buyers also favor pink topaz. The
biggest market for blue topaz is in the US, where it provides a gem alternative that’s lower in cost and more
intense in color than aquamarine.
Topaz carving from Idar-Oberstein
The biggest faceted gem (by weight) ever recorded is a topaz in the
collection of the Smithsonian Institution. Named the “American Golden,”
it’s a light yellow stone that weighs 22,982 cts. (4.60 kg or 10.14 lb.) and
measures 17.3 cm × 14.9 cm × 9.2 cm (6.7 in. × 5.8 in. × 3.6 in.).
Today, topaz is one of the US birthstones for November. (The other is
citrine.) Topaz is a hard stone, but it can develop cleavage. Keep this in
mind when you’re showing jewelry, and advise customers to be a little extra
careful when wearing this gem.
Sources
Australia
Brazil
Madagascar
Mexico
Myanmar (Burma)
Namibia
Nigeria
Pakistan
Sri Lanka
United States
115
Hardness & Toughness
Hardness
Toughness
Stability
8 on Mohs scale
Poor due to cleavage
Environmental Factor
Heat
Light
High heat can alter color; sudden temperature change
can cause breaks
Generally stable, but some brown stones fade
Chemicals
Treatments
Reaction
Affected very slightly
Treatment
Purpose
Stability
Irradiation
followed by heat
Stable
Heat
Stable
Changes some
yellow, orange, or
brown material
to pink
Prevalence
Common
Detection
Produces various
shades of blue
from colorless
material
Routine
(almost all
medium to dark
blue topaz is
produced by
treatment)
Usually undetectable, but
assumed
because of
prevalence.
Occasionally
detectable by a
gemological
laboratory.
Caution: May
very rarely be
dangerously
radioactive*
Undetectable,
but usually
assumed
because of
prevalence
* If there is any doubt, send the gem to a gemological laboratory for verification.
Blue topaz
9.73-ct. topaz from Brazil
116
Care and Cleaning
Type of Cleaning
Advisability
Steam cleaning
Never
Ultrasonic cleaning
Warm, soapy water
Imitations
Never
Safe
Glass
Synthetic sapphire
Synthetic spinel
Alternatives
Aquamarine
Citrine
Hessonite garnet
Kunzite
Malaya garnet
Morganite
Sapphire
Smoky quartz
Spessartine garnet
Spinel
Tourmaline
Topaz crystal
Zircon
117
Tortoise Shell
Tortoise shell is an organic gem material from the shell
of the hawksbill sea turtle. It ranges from semitransparent to translucent, with a mottled appearance that’s usually yellow and brown, but occasionally black and
white. For centuries, artisans used tortoise shell to make
jewelry and other items, including combs and decorative furniture inlays. It was also a popular material for
eyeglass frames and guitar picks.
Hawksbill turtles are an endangered species. Since
the 1970s, they’ve been protected under the UN
Convention on International Trade in Endangered
Species of Fauna and Flora (CITES). Most of the more
than 100 countries that are parties to the convention also
have supporting laws or regulations that ban commerce
in tortoise shell.
US federal law prohibits the import or sale of items
made from hawksbill shell, unless they can be proven to
be at least 100 years old. Pieces that aren’t that old, but
were made and privately owned before 1974, can be
legally purchased from individuals or estates, but only
for a collection, and not for resale.
Hardness & Toughness
Hardness
Toughness
118
21/2 on Mohs scale
Fair
Stability
Environmental Factor
Heat
Light
Treatment
Lamination
(pieces are softened and joined
together with heat
and pressure)
Softens at the temperature of boiling water; high heat
darkens, then burns the material
May darken with age
Chemicals
Treatments
Reaction
Attacked by nitric acid
Purpose
Made thicker
material for
carving
Stability
Variable,
depending on
how well the
layers were
joined
Prevalence
Occasional
Detection
Detectable by a
trained gemologist
or gemological
laboratory*
* If there is any doubt, send the gem to a gemological laboratory for verification.
Care and Cleaning
Type of Cleaning
Advisability
Steam cleaning
Never
Ultrasonic cleaning
Warm, soapy water
Imitations
Plastic
Alternatives
Never
Safe, but hard-bristle brushes can
leave scratches
Tortoise shell box
Agate
Amber
Sardonyx
Shell
119
Tourmaline
People have probably used tourmaline as a gem for centuries, but until the
development of modern mineralogy, they identified it as some other stone
(ruby, sapphire, emerald, and so forth) based on its color. Portuguese explorers,
for example, discovered deposits of green tourmaline in Brazil in the mid1500s, but they thought it was emerald.
The confusion about the stone’s identity is even reflected in its name,
which comes from toramalli, which means “mixed gems” in Sinhalese (a
language of Sri Lanka).
In the late 1800s, tourmaline became known as an American gem through
the efforts of Tiffany gemologist George F. Kunz. He wrote about the tourmaline deposits of Maine and California, and praised the stones they produced. In spite of its American roots, tourmaline’s
biggest market was in China, where the imperial court
prized tourmaline as a material for small carvings and
utilitarian objects like snuff bottles.
The supply of tourmaline began to expand during the
first half of the twentieth century, when Brazil yielded
some large deposits. Then, beginning in the 1950s,
additional finds appeared in countries around the world.
Tourmalines come in a wide variety of exciting colors. In fact, tourmaline has one of the widest color
ranges of any gem species. It occurs in various shades
of almost every hue, and there are a number of trade
names for its color varieties:
• Rubellite—pink, red, purplish red, orangy red, or
brownish red. (Some in the trade argue that pink
tourmaline shouldn’t be called rubellite.)
• Indicolite—dark violetish blue, blue, and greenish
blue.
• Paraíba tourmaline—intense violetish blue, greenish
blue, or blue from the state of Paraíba, Brazil. (This
variety was discovered in 1988.)
• Chrome tourmaline—intense green. (Much of this is
colored by vanadium, the same element that colors
many Brazilian and African emeralds.)
120
• Parti-colored tourmaline—tourmaline with more than one color. One of
the most common combinations is green and pink, but many others are
possible.
• Watermelon tourmaline— pink in the center and green around the outside. Crystals of this material typically have a pink core surrounded by
green, and they’re cut in slices.
Some tourmalines also show chatoyancy. Cat’s-eye tourmalines are most
often green, blue, or pink, with an eye that’s softer and more diffused than
the eye in fine cat’s-eye chrysoberyl. This is because, in tourmaline, the
effect is caused by thin tube-like inclusions that occur naturally during the
gem’s growth. The inclusions are larger than the inclusions in cat’s-eye
chrysoberyl, so the chatoyancy isn’t as sharp. Like other cat’s-eyes, these
stones have to be cut as cabochons to bring out the effect.
Sources
Afghanistan
Brazil
Kenya
Bi-colored emerald cut tourmaline set with diamonds
Major source
Madagascar
Mozambique
Myanmar (Burma)
Namibia
Pakistan
Russia
United States
Hardness & Toughness
Hardness
Toughness
Stability
7 to 71/2 on Mohs scale
Fair
Environmental Factor
Heat
Light
Chemicals
Reaction
High heat can alter color; sudden
temperature change can cause
fracturing
Generally stable
None
121
Treatments
Treatment
Purpose
Stability
Irradiation
Produces deep
pink, red, or purple from very
light pink, green,
blue, or colorless
material; converts
some light yellow
or green material
to a darker yellow
or orange; turns
some green
stones into red
and green particolored
Heat
Acid
Sealing tubes in
cat’s-eye material
with plastic or
epoxy resin
Prevalence
Detection
Lightens very
Stable
dark green or
blue-green
stones; converts
brownish purple
stones to “rose”
pink; produces
bright greenish
blue to yellowish
green stones from
grayish Paraíba
material
Common
Undetectable
Fair to good.
Color may fade
under high heat
or very prolonged
exposure to bright
light.
Common for
pink, red, and
purple.
Occasional for
yellow, orange,
and parti-color.
Undetectable
Improves the
appearance of
cat’s-eye stones
Stable
Occasional
Undetectable
Prevents dirt
from getting
into the tubes
that cause the
cat’s-eye effect
Fair. Heat and
Occasional
solvents can
damage or destroy
the sealant.
Detectable by a
trained gemologist
or gemological
laboratory*
* If there is any doubt, send the gem to a gemological laboratory for verification.
Care and Cleaning
Type of Cleaning
Advisability
Steam cleaning
Risky
Ultrasonic cleaning
Warm, soapy water
122
Risky
Safe
Imitations
Glass
Synthetic ruby
Synthetic sapphire
Synthetic spinel
Alternatives
Almandine garnet
Amber
Amethyst
Aquamarine
Cat’s-eye chrysoberyl
Chrysoberyl
Freshwater cultured pearl torsade with decorative
clasp featuring tourmaline slices.
Citrine
Emerald
Fire opal
Kunzite
Malaya garnet
Morganite
Peridot
Pyrope garnet
Rhodolite garnet
Ruby
Sapphire
Smoky quartz
Spessartine garnet
Spinel
Tanzanite
Topaz
Tsavorite garnet
Zircon
123
Tsavorite
Tsavorite/Grossular/Garnet
Kenya’s Tsavo National Park is home to some of the largest remaining populations of Africa’s legendary animals, including lions, elephants, giraffes,
and zebras. In the early 1970s this wildlife wonderland also gave the world
an exciting new gem. Scientists identified the stone as a transparent green
variety of the garnet species known as grossular. In 1974, Tiffany & Company
introduced it to the US market as tsavorite. (It’s often called tsavolite in
Europe.)
Only a few sources of tsavorite have been discovered, so supplies of it
are limited. Because of its often delightfully bright color, it has become one
of the most sought-after and expensive garnets. Its
color ranges from light to dark—but always intense—
yellowish green or green. You’re likely to see tsavorite
only in fairly small sizes—from about 50 pts. to 3 cts.
The largest faceted tsavorite on record weighs a little
under 24 cts.
Because tsavorite is part of the garnet family, it’s a
US birthstone for January. Its intense green color and
the fact that it’s generally untreated make it an exotic,
high-quality alternative to emerald. It’s an intriguing
twentieth century gem that can add zest to any customer’s jewelry collection.
Sources
Kenya
Tanzania
Hardness & Toughness
Hardness
Toughness
124
7 to 7 1/2 on Mohs scale
Fair to good
Stability
Environmental Factor
Heat
Light
Chemicals
Care and Cleaning
Reaction
Sudden temperature change can
cause fracturing
Stable
Slightly attacked by hydrofluoric
acid
Type of Cleaning
Advisability
Steam cleaning
Never
Ultrasonic cleaning
Warm, soapy water
Imitations
Usually safe, but risky if the stone
contains liquid inclusions
Tsavorite garnet and diamonds in gold ring
Safe
Glass
Synthetic emerald
Synthetic spinel
Alternatives
Demantoid garnet
Emerald
Peridot
Tourmaline
125
Turquoise
Turquoise is one of the world’s most ancient gems. Archaeological excavations revealed that Egyptian royalty wore turquoise jewelry as early as 5500
BC, and Chinese artisans were carving it more than 3,000 years ago.
Turquoise is the national gem of Tibet, and has long been considered a stone
that guarantees health, good fortune, and protection from evil.
Turquoise was a ceremonial gem and a medium of exchange for Native
American tribes in the southwestern US. They also used it in their jewelry
and amulets. The Apaches believed that turquoise attached to a bow or
firearm increased a hunter’s or warrior’s accuracy.
The gem’s name comes from the French expression
pierre tourques, or “Turkish stone.” The name, which
originated in the thirteenth century, reflects the fact that
the material probably first arrived in Europe from
Turkish sources.
Turquoise can be translucent to opaque, with a color
that usually ranges from light to medium blue or greenish blue. It’s often mottled, and sometimes has dark
splotches. It might also have veins of matrix running
through it (matrix is its surrounding rock). In the material known as spiderweb turquoise, fine seams of matrix
form attractive web-like patterns. The most valuable
turquoise is an even medium blue, with no matrix, and
the ability to take a good polish.
Turquoise is plentiful and available in a wide range
of sizes. It’s used for beads, cabochons, carvings, and
inlays. Although well known to consumers, its popularity in the mainstream jewelry industry comes and goes.
The biggest and most permanent market is in the
American Southwest. It’s also popular elsewhere,
among customers who are captivated by that region’s
mystery and romance, as well as by the blue of its skies.
Turquoise is one of the December birthstones. (Zircon
is the other option for that month.)
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Sources
China
Iran
United States
Historical source of the finest material (known as
Persian turquoise): No longer commercially important
Hardness & Toughness
Hardness
Toughness
Stability
5 to 6 on Mohs scale
Generally fair to good
Environmental Factor
Heat
Light
Chemicals
Reaction
High heat can cause discoloration
and surface damage
Stable
Dissolves slowly in hydrochloric
acid; can be discolored by chemicals,
cosmetics, and even skin oils or
perspiration
127
Treatments
Treatment
Purpose
Stability
Painting matrix
with black shoe
polish or similar
colorants
Makes the matrix
a desirable color
Backing with
epoxy resin
Adds thickness,
strength, and
weight to pieces
otherwise too
thin to cut
Filling cavities
with metalloaded epoxy
Hides cavities
and imitates
pyrite inclusions
Impregnation
with wax or
plastic (sometimes with dye
added)
Improves the
color and luster
of pale material;
plastic also improves durability
Prevalence
Detection
Excellent to
fair. Plastic is
stable under
normal conditions, but wax
may gradually
deteriorate and
discolor.
Common
Fair. Solvents
can damage or
destroy the
treatment.
Common
Detectable by a
trained gemologist
or a gemological
laboratory*
Good under
normal conditions. Heat or
solvents can
damage or
destroy the
epoxy backing.
Common
Detectable by a
trained gemologist
or a gemological
laboratory if
the stone is unmounted*
Occasional
Detectable by a
trained gemologist
or a gemological
laboratory*
Fair. Heat or
solvents can
damage or
destroy the fillings, and they
may eventually
separate even
under normal
conditions.
Detectable by a
trained gemologist
or a gemological
laboratory*
* If there is any doubt, send the gem to a gemological laboratory for verification.
128
Care and Cleaning
Type of Cleaning
Advisability
Steam cleaning
Never
Ultrasonic cleaning
Warm, soapy water
Never
Safe
Imitations
Glass
Plastic
“Reconstructed turquoise,” usually made of various powdered minerals—
not turquoise—dyed and bonded with plastic, epoxy resin, or similar
substances.
Synthetics
Synthetic turquoise was produced on a limited basis in
the 1980s, but it was never widely available on the market.
A trained gemologist or gemological laboratory can
identify the material. (If there is any doubt, send the gem
to a gemological laboratory for verification.)
Alternatives
Agate
Chrysocolla chalcedony
Jadeite jade
Lapis lazuli
Malachite
Nephrite jade
Turquoise and diamond pin in the form of a closed
flower
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Zircon
Many people have heard of zircon but never seen it. Mostly, this is because
of colorless zircon’s wide use as a diamond simulant in the early 1900s. It
was long ago replaced in that role by more convincing look-alikes, but its
name still means “imitation” to many people. That’s unfortunate—or, rather,
it creates an opportunity for creative customer education—because zircon is
a beautiful colored stone with its own fair share of folklore and charm.
Zircon is one of the US birthstones for December (the alternate is
turquoise). In the Middle Ages, this gem was thought to induce sound sleep,
drive away evil spirits, and promote riches, honor, and wisdom. Many
scholars think the stone’s name comes from the Arabic word zarkun, meaning “cinnabar” or “vermilion.” Others believe the source is the Persian word
zargun, or “gold colored.” Considering zircon’s color range, either derivation seems possible.
The most common color for the zircons on today’s
market is a distinctive greenish blue that’s often called
“zircon blue.” Others include green, yellow, orange,
red, brown, and even purple. The colors are often light
and muted, but the finest stones have strong, rich colors.
Zircon is one of the few colored stones that might
show visible dispersion. When you’re showing this
gem, look for flashes of rainbow-colored fire and point
them out to customers.
The supply of zircon is generally limited, and typical
sizes depend on color. Blue or green stones normally
range from 1 ct. to 10 cts., yellows and oranges up to
around 5 cts., while reds and purples are usually smaller. Most colors are available in various fancy shapes,
but colorless and blue stones are often fashioned in the
style known as the zircon cut—a round brilliant with
eight extra facets around the culet.
Zircon has medium hardness, and the heat treatment
that produces many of its colors might also make zircon
brittle. For this reason, it’s safest to recommend zircon
in earrings or pendants, or in protected ring settings.
This will keep the gem from becoming scratched and
abraded and make it less vulnerable to fracturing.
130
Sources
Australia
Cambodia
China
Myanmar (Burma)
Sri Lanka
Thailand
Vietnam
Hardness & Toughness
Hardness
Toughness
Stability
6 to 71/2 on Mohs scale
Fair to good; heat-treated stones can be brittle and
might be easily abraded
Environmental Factor
Various colors of zircon
Reaction
Heat
High heat can alter color
Chemicals
None
Light
Treatments
Treatment
Heat
Generally stable; some heat-treated stones revert to
their original color (light brown)
Purpose
Produces colorless, blue, yellow,
orange, or red
from brown
material
Stability
Generally stable,
but some stones
revert when
exposed to light
Prevalence
Routine. Almost
all blue or colorless zircons are
treated.
Detection
Undetectable,
but usually
assumed due to
prevalence
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Care and Cleaning
Type of Cleaning
Advisability
Steam cleaning
Risky
Ultrasonic cleaning
Warm, soapy water
Imitations
Risky
Safe
Cubic zirconia
Glass
Blue zircon
Synthetic sapphire
Synthetic spinel
Alternatives
Almandine garnet
Amethyst
Aquamarine
Chrysoberyl
Citrine
Demantoid garnet (also shows strong dispersion)
Fire opal
Hessonite garnet
Kunzite
Malaya garnet
Peridot
Pyrope garnet
Rhodolite garnet
Ruby
Sapphire
Spessartine garnet
Spinel
Brown zircon
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Topaz
Tourmaline
Green zircon, Sri Lanka, 5.68 cts.
ACKNOWLEDGMENTS
The Gemological Institute of America gratefully acknowledges the following people and organizations for
their assistance in providing some of the gems, jewelry, and photography used in this assignment:
23rd St. Shoppe, 43 (top), 77 (bottom), 114, 122, 123 (bottom)
A. Ruppenthal KG, 83 (middle)
Carol Ackerman, 111 (right)
Chris Almquist, 121 (top)
Assael International, 75
Bear Essentials, 33 (bottom)
Jonte Berlon, 124
Matt Bezak, 117 (bottom)
Gordon Bleck, 40, 100, 101 (top left), 102, 107 (bottom), 108, 132 (middle)
Gary Bowersox, 13 (bottom), 27 (middle), 54, 55 (top), 57, 132 (bottom left)
Buccellati, 74 (bottom left)
Alan Caplan, 35 (right)
Carolyn Tyler Designs, 2 (bottom)
Christie’s Images Inc., 34, 46, 88
Don Clary, 27 (top), 81 (bottom)
Cody Opal, 70
Coffin & Trout Jewelers, 125 (top)
Colgem Ltd., 98
Creative Jewelers, 2 (top)
Crescent Jewelers, 55 (middle), 115 (bottom)
Crystal Reflections, 23
Bart Curren, 11 (middle and bottom), 81 (top)
Brian Davenport, 87 (top), 91 (left)
Anil B. Dholakia, Adris Oriental Gem and Art Corp., 43 (bottom)
Dona Dirlam, 81 (top)
Ali Farook, 104
Emmanuel Fritsch, 3 (bottom)
Fu Gemstone Import, 106
Mary Murphy Hammid, 5 (top and bottom)
Herring & J.T. McManus, 12
Herrling-Schmuck, 78
Debbie Hiss-Odell, 39, 90
Hixon Collection, 47 (top)
David Humphrey, 19 (bottom), 71 (left), 130
JCK Magazine, 132 (top)
J. Grahl Design, 10 (bottom), 11 (top), 37 (top), 72, 73 (bottom), 74 (top), 85, 120, 123 (top)
Jim Shaylor Jewelers, 36 (left)
Neil Lane, 16
Ledge Studio, 97 (top)
Glenn Lehrer, 97 (top)
Dave LeRose, 86, 116 (bottom)
Andy Lucas, 61 (top)
Martin Chung Gemstones and Fine Jewelry Co., 13 (top), 56, 61 (top), 84 (bottom)
Mayer & Watt, 5 (top and bottom), 80
Elise Misiorowski, 3 (middle)
Ginger Moro, 8, 96, 129 (right)
Bernd Munsteiner, 121 (bottom)
Natural History Museum of Los Angeles County, 89 (top)
Pala International, 99, 125 (middle)
Peter Secrest Collection, 17 (top)
Smithsonian, 109 (right)
Kent Raible, 73 (top)
Ramsey Gem Imports, 64
Rigoberto Jewelry Designs, 6, 7, 20, 21, 38, 39
Serengeti West, 125 (bottom)
C.Y. Sheng, 26, 27 (bottom)
Silverhorn, 4
Michael Stubin, 17 (bottom right)
Suzanne Tennenbaum, 29 (top)
Tiffany & Co., 13 (middle), 55 (bottom), 110
Van Cleef & Arpels, 88
Harry Winston, 74 (right)
Elizabeth Ziegler, 10 (top)
Benjamin Zucker, 17 (bottom left)
133
PHOTO CREDITS
Sylvia Bissonette, 10 (bottom), 11 (top), 37 (top), 72, 73 (bottom), 74 (top), 85, 120, 123 (top)
Nicholas DelRe, 43 (bottom), 93 (top), 95 (bottom)
Tino Hammid, 2 (bottom), 4, 5 (top, middle, bottom), 6, 7, 10 (top), 16, 17 (bottom left), 19 (middle), 22, 27
(second), 29 (top), 32, 37 (bottom), 38, 39, 43 (top), 47 (top), 55 (middle), 60, 61 (all), 65 (top), 68, 73 (top), 77
(bottom), 80, 81 (top), 84 (top), 90, 100, 101 (top), 107 (top), 114, 115 (bottom), 121 (top), 122, 123 (bottom),
124, 130, 131
Mike Havstad, 29 (bottom), 31 (top), 41, 47 (bottom), 51 (bottom), 59 (top), 66, 69 (top), 71 (right), 97 (bottom
right), 101 (bottom), 116 (left)
John Koivula, 9 (bottom left and right), 33 (top)
Shane McClure, 35 (top), 64, 87 (bottom), 103
Tim Nighswander, 111 (top)
Jeffrey Scovil, 17 (top), 65 (bottom)
Michael Stubin, 17 (bottom right)
Maha Tannous, 33 (bottom), 42 (top)
Harold & Erica Van Pelt, 36 (right)
Fred Ward, 109 (left)
Robert Weldon, 2 (top), 3 (top, middle, bottom), 6 (top), 8, 11 (middle and bottom), 12, 13 (top and bottom), 19
(top and bottom), 23, 25, 26, 27 (top, bottom two), 28, 33 (middle), 36 (left) 40, 42 (bottom), 44, 54, 55 (top), 56,
57, 62 (all), 63 (bottom), 71 (left), 74 (bottom left and right), 75, 81 (bottom), 83 (top and bottom), 84 (bottom),
86, 87 (top), 89 (top), 90, 91 (left), 95 (top), 96, 97 (bottom left), 98, 99, 101 (middle), 102, 104, 106, 107
(bottom), 108, 111 (bottom), 115 (top), 116 (right), 117 (bottom), 121 (bottom), 125 (middle and bottom), 127,
128, 129 (right), 132 (all)
134