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.
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.) Famous Finds
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.
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.