Natural Treasures
Precious Metals
•
•
•
•
Naturally occurring
Metallic elements
Rare
Valuable
Precious Metals
• Graded on:
– Rarity
– Purity
– Mass
Precious Metals
• Silver: current value $22.38 per ounce
• Gold: current value $1323.39 per ounce
Silver
•
•
•
•
•
Uses: coins, jewelry, mirrors, silverware
Found in ores with other elements
Extracted through mining
Major mining operations in Peru, China, and Mexico
Other large mining operations are found in
Australia, Bolivia, Russia,
the US, Poland and Canada,
also Argentina and Chile.
• In the United States, Nevada
is the largest producer.
Gold
• Uses: coins, jewelry, space research and other scientific
advances, dentistry, electronics
• Native gold is often found as an alloy with silver.
• Extracted through mining, “panning for gold” in river
sediments
• China and Australia are the biggest producers of gold.
• Other major gold mining operations take place in the US,
Russia, and South Africa, also South America, Canada,
and Indonesia.
• Gold can be found throughout the country. Mines in South
Dakota and Nevada supply the majority of the gold in the
United States.
Gold Rush!
• Gold was first discovered in the US at the
Reed Gold Mine in North Carolina in 1803.
• After that, gold rushes took place in
Georgia, California, Colorado, and the
Black Hills.
• Similar gold rushes took place in New
Zealand, South Africa, and the Klondike
region of Canada.
Famous Finds
• Holtermann Nugget
– found by Bernhardt
Holtermann in Australia
in 1872
– weighed in at just under
640 lbs.
Famous Finds
• Welcome Stranger
– found by John Deason and Richard Oates in
Australia in 1869
– weighing in at 2316 troy ounces (about 159 lbs.)
Famous Finds
• Hand of Faith
– found by Kevin Hiller in
Australia in 1980
– 876 troy ounces
(almost 62 lbs.)
Mining
• Sluicing
• Dredging
• Hard-rock mining
Processing
• Grind rocks containing gold.
• Add sodium cyanide to dissolve it.
• Collect the new gold cyanide solution and
add zinc to form a precipitate.
• Add sulfuric acid to remove the zinc.
• Collect the gold sludge and put it through
a smelting process.
• Ship the gold to a metal refinery for final
processing.
Processing
• There, it is melted again and borax and
soda ash are added, to remove unwanted
impurities.
• Depending on its intended usage, the pure
gold is then mixed with other metals to
form an alloy.
• Gold ingots are formed.
Precious Gems
• Pretty minerals used to make jewelry
• Graded based on
– Color
– Cut
– Clarity
– Carats (size)
Precious Gems
• Precious gemstones
– Diamond
– Ruby
– Emerald
– Sapphire
Diamond
• Formed from pure carbon
• Hardest known material
• Used in jewelry as well as in cutting and
polishing tools
• Formed under high temperature and
pressure beneath the Earth’s surface,
over a long period of time
Diamond
• Primary source: brought up by volcanic
activity
• Secondary source: dispersed by erosion
Diamond Mining
• Ore is crushed, then diamonds are sorted by
density.
• The raw diamonds are traded or sold.
• Raw diamonds are then hand-picked, cut and
refined.
Diamond Mining
• Today, the most productive diamond mining
operations are in Africa, Russia, Australia, and China.
• There are also productive diamond mines in India,
Canada and Brazil.
• In the US, diamonds have been found in about a third
of the states.
• http://dsc.discovery.com/tv-shows/dirtyjobs/videos/outback-treasure-hunter.htm
Diamond Mining
• Blood diamonds
Diamond
• Color in diamonds comes from impurities.
– Nitrogen is the most common and creates the yellow
and brown color of most diamonds.
• Synthetic diamonds
• Almost diamonds
Famous Finds
• The Cullinan diamond is
the largest gem-quality
diamond ever found, at
3106.75 carat (about
1.37 lb.) rough weight.
• It was found in South
Africa in 1905.
Famous Finds
• The Golden Jubilee is the largest
faceted diamond in the world.
• At 545.67 carats, it is larger than
the Cullinan I, the largest
diamond cut from the Cullinan
raw stone, though it came from
the same legendary mining
grounds.
Famous Finds
• Possibly the world’s most famous
diamond
• Valued at $250 million
• It has a long recorded history, dating
back to the late 17th century.
• It has changed hands numerous
times, from the kings of France to its
home at the Smithsonian in the
United States.
• Supposedly cursed
Famous Finds
• The Patiala necklace featured 2,930
diamonds, including the 428 carat
De Beers diamond as its centerpiece.
• The necklace disappeared in 1948.
• When it was recovered 50 years
later, the largest diamonds
were missing.
Recent News
• A flawless 59.6-carat pink diamond will be
auctioned in Geneva this fall at a record
asking price of $60 million dollars.
• The gem, which is known as the “Pink Star,”
was mined by De Beers (a major mining
conglomerate) in Africa in 1999.
Ruby
• Crystals formed by the mineral corundum
(aluminum oxide)
• Red color comes from the element
chromium
• Color is the most important factor in
determining a ruby’s value.
• After color come clarity,
size and cut.
Ruby
• Myanmar region famous for rubies
• Most rubies come from Asia and Africa.
• Rubies have also been found in Australia,
Greenland, Brazil, and the US.
Mining Gems
• Blasting
• Digging
• Dredging
Ruby
• Rubies may be altered before they are
used in jewelry.
• Heat treatment
– improves color
– removes inclusions
• Repairing cracks
– lead glass used to fill fractures
Ruby
• Synthetic rubies can be produced.
• Used in red lasers
Famous Rubies
• A ruby recently found in Greenland may be
the world’s largest rough ruby. The crystal
weighs 8.2 lbs. or 18,696 carats.
Famous Rubies
• American billionaire Lily Safra’s ring,
containing The Hope Ruby (a Burmese
ruby of 32.08 carats) was sold at auction
in 2012 for $6,742,440.
• A ring belonging to Elizabeth Taylor which
featured an 8.24 carat gem sold for
$512,925 per carat (over $4.2 million in
total) at an auction in 2011.
Star Rubies
• The Midnight Star
• 116.75 carats
• Natural History
Museum in NYC
Star Rubies
• Delong Star Ruby
• 100.32 carats
• Natural History
Museum in NYC
Star Rubies
• Rosser Reeves Ruby
• 138.7 carats
• Donated to the
Smithsonian in 1965
Sapphire
• Crystals formed by the mineral corundum
• Traces of titanium and iron produce the blue color.
• Other colors created by different chemical impurities
Sapphire
• Form as molten rock cools slowly beneath
the Earth’s surface
• Mined from primary sources
(underground) or from alluvial deposits
• Most of the world’s sapphires come from
Asia and Africa.
• Other major sapphire mining operations
take place in Australia, Brazil, Greenland,
and North America.
Sapphire
• Sapphire is mined in much the same way
as ruby.
• It is treated prior to being used in jewelry.
• Diffusion treatments may enhance a
sapphire’s color.
Famous Sapphires
• Millennium Sapphire
• Discovered in Madagascar in 1995
• The world’s largest sapphire, at 61,500
carats in weight
Famous Sapphires
• Logan sapphire
• 423-carats
• National Museum of
Natural History in
Washington, D.C.
• One of the
largest faceted blue
sapphires in existence
Famous Sapphires
• The record price-per-carat for sapphire at
auction was achieved by a sapphire from
Kashmir in a ring, which sold for more than
$175,000 per carat (more than $3.4 million
in total) in May of 2013.
Star Sapphires
• Black Star of Queensland
• The largest gem-quality
star sapphire in the world
• 733 carats
Star Sapphires
• The Star of India
• 563.4 carats
• Museum of Natural
History in NYC
Star Sapphires
• The Star of Bombay
• 182-carats
• National Museum of
Natural History in
Washington, D.C.
Emerald
• Emerald is formed by the mineral beryl
with chromium or vanadium inclusions.
• Minerals dissolved in hot water beneath
the Earth’s surface cool and slowly form
crystals.
• Color and transparency are the most
important attributes.
Emerald
• Emeralds are found all over the world.
• Columbia is by far the world's largest
producer of emeralds.
• In the US, emeralds have been found
in Montana, Nevada, Connecticut, and the
Carolinas.
• More recently, emeralds have been found
in the Yukon.
Emerald Mining
Emerald
• Emeralds are often enhanced before sale
by adding oils which improve their luster.
Famous Emeralds
•
•
•
•
Patricia Emerald
Found in Colombia in 1920
632 carats
Special because the
crystal is 12-sided
Famous Emeralds
•
•
•
•
Gachala Emerald
found in 1967 in Colombia
858 carats
now at the Smithsonian
Famous Emeralds
•
•
•
•
Duke of Devonshire Emerald
Discovered in Columbia
Presented to the duke of Devonshire in 1831
1383.95 carats
Famous Emeralds
• Teodora emerald
• This 57,500 carat
stone may be the
world's largest cut
emerald.
• Up for auction,
expected to bring a
price of $1.15 million
• Originally found in
Brazil
Famous Emeralds
•
•
•
•
•
•
•
•
•
Bahia emerald
At 840 lbs., the largest single emerald crystal ever found
Valued at $400 million
First discovered in Brazil in 2001
Found in a storage basement in New Orleans after
Hurricane Katrina
Reported stolen in 2008 from a secured vault near Los
Angeles
At one point, it was listed on eBay with a Buy it Now
price of $75 million!
Several competing claims of ownership
Eventually, the emerald was taken into the custody by
the Los Angeles Sheriff's Department. The case will be
decided in court in 2013.
Famous Emeralds
•
•
•
•
•
Chalk Emerald
Columbian emerald
37.82 carats
Belonged to a noblewoman in India
In the 20th century, the emerald
was recut and set in a ring
designed by Harry Winston Inc.
• The Chalk family donated it
to the Smithsonian in 1972.
Famous Emeralds
•
•
•
•
•
•
•
Mogul emerald
217 Carats
Originally from Columbia
Cut and sold in India to a Mogul noble
Engravings date back to late 1600’s
Sold at an auction in 2001 for over $2 million
Now in a museum in Qatar
Famous Emeralds
• Imperial Emerald
• 206 carats
• Amazing color and transparency,
completely unenhanced
• Being offered for sale by New York
company Bayco Jewels at the gem
exhibition in Switzerland this year
Pearl
• Calcium carbonate deposits formed by shellfish
• Found in freshwater and marine environments
around the world
• Japanese pearls, Indonesian South Sea pearls,
and Tahitian pearls are the most famous.
Pearl
• Pearls may be natural, farmed, or imitation.
• Of these, natural pearls are the rarest
• Perfectly round and shiny pearls are the
most desirable.
• Colors may vary from white or cream to
yellow, pink, or black.
Harvesting Pearls
Famous Pearls
• The Pearl of Lao Tzu (also known as The
Pearl of Allah) is the largest known pearl.
• Recovered from a giant clam in the
Philippines in 1934
Famous Pearls
• Other famous pearls include
necklaces worn by royalty.
• Rare necklaces have sold at
auction for $1-3 million.
• A necklace worn by the
Baroda nobility of India sold
for over $7 million.