Minerals
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Natural
Solid
Inorganic
Definite chemical
composition
Crystal structure due
to internal arrangement
of atoms
http://www.minerals.net/gemstone/index.htm
http://www.mii.org/www.mii.org
General Facts about Minerals
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Between 2 - 3,000 have been identified
A few are “native elements” -- made of only
one element, such as sulfur, gold. copper,
and graphite (carbon)
Most are compounds, especially the silicate
group (Si, O).
Other important groups are oxides,
carbonates, and sulfides.
Less than a dozen are common in
most rocks
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Quartz
Feldspar (group)
Muscovite (white mica)
Biotite (black mica)
Calcite
Pyroxene
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Olivine
Amphibole (group)
Magnetite, limonite,
and other iron oxides
Pyrite
Common uses include:
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Aluminum--packaging, transport, building
Beryllium--gemstones, fluorescent lights
Copper--electric cables, wires, switches
Feldspar--glass and ceramics
Iron--buildings, automobiles, magnets
Calcite--toothpaste, construction
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http://www.mii.org/commonminerals.php
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Minerals are identified by their key
characteristics
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hardness
crystal shape (form)
luster
color
streak
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cleavage/fracture
density (specific
gravity)
special properties -reaction to acid -fluorescence
-salty taste
-magnetism
1. Mineral Hardness
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Ability to scratch
another mineral
Mohs scale from 1
(talc) to 10 (diamond)
Quartz (most common
mineral and most dust
particles) is 7
http://mineral.galleries.com/minerals/elements/diamond/diamond.htm
2. Crystal Shape (Form)
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External structure due
to internal arrangement
of the atoms
Six basic groups of
shapes, with about
three dozen variations
http://www.minerals.net/mineral/carbonat/aragonit/aragoni1.htm
3. Luster
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Describes how light
reflects off the surface
Main categories are
“metallic” and “nonmetallic”
Non-metallic includes
“dull,” glassy,” waxy,”
“pearly,” and others
http://www.minerals.net/mineral/s
ulfides/pyrite/pyrite2.htm
http://www.minerals.net/mineral/sulfides/pyrite/pyrite2.htm
4. Color
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results from ability to
absorb some
wavelengths and
reflect others
some minerals have
characteristics colors
others vary due to
chemical differences
or impurities (atoms
mixed inside the main
elements)
http://www.minerals.net/mineral/carbonat/calcite/images/4assortd.htm
5. Streak
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Color of the powder
when rubbed on a
“streak plate”
(unglazed porcelain)
May be same as
hand-specimen or
different
Some paint is based
on powdered minerals
(streaks).
http://www.minerals.net/mineral/oxides/hematite/hematit6.htm
6. Mineral cleavage/fracture
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Some minerals split along flat surfaces when
struck hard--this is called mineral cleavage
Other minerals break unevenly along rough
or curved surfaces--this is called fracture
A few minerals have both cleavage and
fracture
7. Density (Specific Gravity)
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All minerals have
density (mass / volume),
but some are very
dense
Examples include
galena, magnetite, and
gold
Specific Gravity is the
density of the mineral
compared with density
of water
http://www.minerals.net/mineral/elements/gold/gold1.htm
Special Characteristics-1. the “Acid Test”
Carbonates react with
dilute HCl and other
acids by fizzing or
bubbling (releasing
CO2 gas)
Special Characteristics-2. Fluorescence
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Some minerals will
glow when placed
under short-wave or
long-wave ultraviolet
rays
Franklin and
Ogdensburg NJ are
famous for their
fluorescent minerals
http://www.sterlinghill.org/Tour%20information.htm
Special Characteristics-3. Salty Taste
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DO NOT TASTE MOST
MINERALS!
Halite is the exception-it will taste salty
http://mineral.galleries.com/scripts/item.exe?LIST+Minerals+Halides+Halite
Special Characteristics-4. Magnetism
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Many iron minerals will
produce an invisible
magnetic force field
“Lodestone” was used
by Vikings more than
1,000 years ago as
compasses
http://www.minerals.net/mineral/oxides/magnetit/magneti4.htm
Mineral Identification Key
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I. Mineral has a colored streak
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A. Mineral has a black or grayish streak.
B. Mineral leaves a brown or reddish-brown streak.
C. Mineral leaves either a blue or a green streak.
II. Mineral does not leave a colored mark on streak
plate, but leaves a white streak or scratches the
streak plate.
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A. Mineral will scratch glass
B. Mineral will not scratch glass but will scratch a penny.
C. Mineral will not scratch a penny, and cannot be
scratched by your fingernail.
D. Mineral can be scratched by your fingernail.
Mineral Identification Key
I.
Mineral has a colored streak.
A. Mineral has a black or gray streak.
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1. Has a metallic gold
appearance. It leaves a
black Streak.= Pyrite
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2.Leaves a “lead gray”
streak, and has a bright
silver metallic luster.
It’s heavy.= Galena
I. A. Mineral has a black or grayish streak.
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3. Will write on paper
(easily), and feels
greasy. = Graphite
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4. Is “magnetic” =
Magnetite
I. B. Mineral leaves a brown or reddishbrown streak.
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1. Has brown circles
on it’s surface. =
Bauxite
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2. Has a bumpy
surface. = Hematite
I. C. Mineral leaves either a blue or a green
streak.
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1. Green streak. =
Malachite
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(Often appears with
Azurite.)
2. Blue streak.=Azurite
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(Often appears with
Malachite)
Mineral Identification Key
II. No colored mark on the streak plate, but
leaves a white streak or scratches streak plate.
II. A. Will scratch glass. Hardness 6-10
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1. Clear or translucent.
Has a hardness of 7.=
Quartz
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If Pink = Rose Quartz.
If Dark = Smoky Quartz.
II. A. Mineral will scratch glass
Hardness: 6-10
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5. Is orange and white in
color. It has a hardness
of 6. Distinct 90 ̊
cleavage. = Feldspar
3. Mineral is reddishpurple in color and has a
hardness of 9. =
Corondum
II. B. Mineral will not scratch glass, but
will scratch a penny. Hardness: 4-5
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1. Mineral is light
green in color and
has a hardness of 5.
= Apatite
5. Translucent and
writing appears
double when looking
through it. = Calcite
II. B. Mineral will not scratch glass, but
will scratch a penny.
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4. Transparent to
translucent. Mineral
varies in color. It is
often purple. Often
shows good
cleavage. =
Fluorite
II. C. Mineral will not scratch a penny, and cannot be
scratched by your fingernail. Hardness: 2-3
1. Mineral has cubic
cleavage and tastes salty.
= Halite
2.Is in think flat sheets and
peels off in layers. In
Mica Family.
-Dark Mica=Biotite
-Light Mica=Muscovite
II. D. Mineral can be scratched by your
fingernail. Hardness: 1-2
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1. Mineral feels
soapy and has a
hardness of one. =
Talc
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2. Transparent or
translucent and has
good cleavage.
Mineral has silky
luster and hardness
of two. = Gypsum
Useful Web Sites
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www.mii.org
www.mineral.galleries.com/minerals
www.mineral.net
www.usgs.gov
http://geology.about.com/library/bl/images/bl
mineralindex.htm