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Crystallized Gold in Quartz

The Mineral gold

Gold is one of the most popular and well-known minerals, known for its value and special properties since the earliest of time. Most of the natural Gold specimens that have been found since early times have been smelted for production. Nice specimens, therefore, are regarded very highly, and are worth much more than the standard gold value. Only recently have more specimens been available to collectors, as more miners have been saving some of the larger pieces for the collectors market.

Gold in its natural mineral form almost always has traces of silver, and may also contain traces of copper and iron. A Gold nugget is usually 70 to 95 percent gold, and the remainder mostly silver. The color of pure Gold is bright golden yellow, but the greater the silver content, the whiter its color is. Much of the gold mined is actually from gold ore rather then actual Gold specimens. The ore is often brown, iron-stained rock or massive white Quartz, and usually contains only minute traces of gold. To extract the gold, the ore is crushed, then the gold is separated from the ore by various methods.

Gold nuggets, a popular form of Gold with collectors, are formed when erosion causes a large piece of Gold to separate from its mother rock, and then gets carried into a stream or river. The flowing water tumbles the Gold, giving it its distinct rounded shape. The Gold eventually settles at the bottom of the water, and due to its heaviness remains there. Other nuggets also get caught in the same area, forming a placer deposit.

Gold is one of the heaviest minerals. When pure, it has a specific gravity of 19.3. Due to its weight, it can be panned because the Gold sinks to the bottom. In addition, it can be easily separated from other substances due to the weight differences. Gold is also the most malleable and ductile substance known. It can be flattened out to less than .00001 of an inch (less than .000065 cm), and a 1 oz. (28 gram) mass can stretch out to a distance of over 50 miles (75 kilometers). Gold is also one of the most resistant metals. It won't tarnish, discolor, crumble, or be affected by most solvents. This adds on to the uniqueness and allure of this mineral.

Gold is usually associated with Pyrite and other sulfides, and sometimes may not be noticed because of the association with these resembling minerals. In certain localities, minerals that contain these sulfides are heated high enough for the sulfides to dissolve, enabling the Gold to remain intact on the matrix. Such Gold is known as "Roasted Gold", and is occasionally sold to collectors.

For additional information, see the gemstone section on Gold.
Chemical Formula Au
Composition Gold, with small amounts of silver; sometimes also copper and iron
Variable Formula (Au,Ag) ;
Color Golden yellow to brass yellow
Streak Golden yellow
Hardness 2.5 - 3
Crystal System Isometric
3D Crystal Atlas
(Click for animated model) 
Crystal Forms
and Aggregates
Octahedral, dodecahedral, and cubic crystals occur, as well as combinations of these forms, but they are uncommon and are often distorted. Dendrites, wires, nuggets, encrustations, and small flakes are the more common forms. Crystals are often stacked into elongated groups, and may form in lines or patterns, especially in herringbone formation. Spinel twinning in groups of small crystals is well-known habit. Crystals may form in hopper growths.
Transparency Opaque
Specific Gravity 15.5 - 19.3
Luster Metallic
Cleavage None
Fracture Hackly
Tenacity Ductile and malleable
Other ID Marks Excellent conductor of electricity
Complex Tests Soluble only in aqua regia
In Group Native Elements
Striking Features Golden-yellow color, extreme heaviness, lack of tarnish, and malleability and ductility
Environment In Quartz veins and high temperature hydrothermal deposits, as well as placer deposits.
Rock Type Sedimentary, Metamorphic
Popularity (1-4) 1
Prevalence (1-3) 3
Demand (1-3) 1

Native Gold

 -  Alloy of Silver and Gold, with the gold content about 75%.
 -  Mixture of Gold veins within a Quartz matrix.

Gold has been used as a precious metal throughout the history of mankind. This is due to its resistance, beauty, rareness, and the fact that it is very easy to work with. Many exotic gold ornaments from the past have been found. Especially noteworthy are the golden ornaments from the tombs of the Pharaohs in Egypt, where gold masks, statues, coins, and much jewelry was archeologically excavated. Gold has been used for coinage throughout the centuries, and is currently accepted internationally as a standard value. Nowadays, the main use of gold is for jewelry. As pure gold is easily bent and dented, it is always alloyed with other metals when used in jewelry. This makes it more durable and practical for ornamental use. The purity of the gold based on the alloyed metal is measured in karat weight. The karat measurement determines the percentage of gold to other metals on a scale of 1 to 24 , with 24 karats being pure gold. Due to gold's distinctive properties as a metal, it has several industrial uses. It is used in photography, dentistry, coloring, and is currently being studied for cancer treatments.

Much of the Gold mined is from large mining operations where the Gold is smeltered for commercial use, and although many commercial gold mines exist, mineral specimens and crystals are hard to come across. China and South Africa have been the worlds two largest Gold producers, but collectors will rarely if ever see a Gold specimen from these countries due to the restrictive nature of the mining operations. This locality list will restrict itself to specific occurrences where noteworthy specimens extracted have made their way to collections.

Australia, a large gold producer, has the famous occurrences of Kalgoorlie, Western Australia; and the Bendigo area, Victoria. An odd occurrence from a country with few known mineral deposits is the Porgera Mine, Enga Province, Papua New Guinea. The Pacific Island of Fiji is also known for its production of Gold in the Emperor Mine, Viti Levu.

In Europe, a classic occurrence is Rosia Montana, Transylvania, Romania. Other European occurrences are the Björkdal mine in Vasterbotten, Sweden; Brusson, Val D'Aosta, Italy; and Hope's Nose, Torquay, Devon, England. Two well-known South American occurrences are Itaituba, Pará, Brazil and the Bolivar province, Venezuela.

Well known Gold localities in Canada are the Timmons area, Ontario; the Red Lake Gold District, Ontario; and the Dawson Mining District, Yukon Territory.

In the U.S., the most famous Gold producing states are California, Nevada, South Dakota, and Alaska. California, home to the Gold rush in the Sierra Nevada Mountains, abounds in historical mining towns and many scattered occurrences. Many are long forgotten, but here is a list where some very fine specimens have come from. The Eagle's Nest Mine, Placer Co., (which has produced some of the best specimens for the mineral market); Placerville, El Dorado Co.; Grass Valley and the Red Ledge Mine, Nevada Co.; the Colorado and Mockingbird Mines, Mariposa Co.; and the Sixteen-To-One Mine, Calaveras Co.

Two famous Gold regions in Nevada are the Round Mountain Mine, Nye Co., and the Olinghouse District, Washoe Co. Colorado has many minor occurrences but well known localities are the Dixie Mine, Clear Creek Co.; Breckenridge, Summit Co.; and Cripple Creek, Teller Co. Alaska has many placer deposits in the streams in rivers, and a few of the names that are familiar are the Kenai Peninsula District; the Valdez Creek District; the Hatcher Pass District; the Caribou Creek District; and the Petersville District. The state of Alaska has preserved many of these historical placer deposits for public recreational mining.

Quartz, Pyrite, Arsenopyrite, Silver, Sphalerite, Galena, Limonite

Pyrite (also known as "Fools" Gold) - different streak (black), less dense (4.8 - 5.2), harder (6 - 6½)
Chalcopyrite - different streak (black), less dense (4.1 - 4.3), harder (3½ - 4)

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