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Chemical Formula | Au | ||
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Composition | Gold, with small amounts of silver; sometimes also copper and iron | ||
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Variable Formula | (Au,Ag) ; (Au,Ag,Cu,Fe) |
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Color | Golden yellow to brass yellow | ||
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Streak | Golden yellow | ||
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Hardness | 2½ - 3 | ||
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Crystal Forms and Aggregates |
(Isometric) Octahedral, dodecahedral, and cubic crystals occur. Crystals are very uncommon and are usually distorted. Dendrites, wires, nuggets, and small flakes are more common. | ||
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Transparency | Opaque | ||
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Specific Gravity | 15.5 - 19.3 (100% pure Au = 19.3) | ||
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Luster | Metallic | ||
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Cleavage | None | ||
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Fracture | Hackly | ||
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Tenacity | Ductile and malleable | ||
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Other ID Marks | Excellent conductor of electricity | ||
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Other Names |  Native Gold |
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Varieties |  Picture Rock - Mixture of
Gold and Quartz found in gold yielding quartz veins. Electrum
- Alloy of silver and gold, with the gold content
about 75%. |
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In Group | Native elements ; Metallic elements | ||
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All About | The mineral Gold is almost always mixed with
a small amount of silver, and sometimes contains traces
of copper and iron. A Gold nugget is usually 70 - 90
percent gold, and the remainder mostly silver. The color
of pure Gold is bright golden yellow, but the greater the
silver content, the whiter the color. Most Gold is mined from ore, containing tiny amounts of Gold in the ore. The ore is brown, iron-stained rock or massive white Quartz. To extract the gold, the ore is crushed, then the gold is separated from the ore by various methods. Gold is less commonly found as nuggets. Nuggets are formed when erosion causes a large piece of Gold to separate from its mother rock, and then gets carried away into a stream or river. The flowing water tumbles the Gold, giving each specimen a distinct 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. An even rarer form of Gold is as crystals, which are cubic, octahedral, and dodecahedral. Even when the Gold occurs in crystals, they are distorted or are almost microscopic. The finest 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. Gold is one of the heaviest minerals, and therefore can be panned easily because the Gold sinks to the bottom, below the other substances. In addition, it can be easily separated from other substances due to the weight differences. Gold is 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 of this mineral. Gold is usually associated with Pyrite and other sulfides, and many times cannot 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 depart, enabling the Gold to remain intact on the matrix. Such Gold is known as "Roasted Gold", and is occasionally sold in "rock shops". |
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Uses | 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. In addition, in the olden days
gold didn't have to be extracted, because a large amount
was found in a pure state. Many gold ornaments from the
past have been found. Most noted are from the tombs of
the Pharaoh 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. Due to gold's distinctive properties as a metal, it has several industrial uses. It is also used for photography, dentistry, coloring, and being studied for treatments in cancer. Also see the gemstone section on Gold |
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Striking Features | Golden-yellow color, extreme heaviness, lack of tarnish, and extreme malleability and ductility | ||
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Complex Tests | Soluble only in aqua regia | ||
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Popularity (1-4) | 1 | ||
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Prevalence (1-3) | 3 | ||
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Demand (1-3) | 1 | ||
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Distinguishing Similar Minerals |
Pyrite and Marcasite - 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) Only tiny flakes or crystals of these three minerals can possibly be confused with Gold, because the differences are easily noticed. These minerals are more pale than Gold, but occasionally exhibit a more intense yellow like Gold. |
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Commonly Occurs With |
Quartz, Pyrite, Arsenopyrite, Silver | ||
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Noteworthy Localities |
Although Gold is a rare mineral, it has many scattered occurrences. Most of these occurrences usually lack quality and quantity in regard to Gold. However, certain regions contribute greatly to the gold market. Some of the best known Gold producing regions are: California, Colorado, Ontario, Mexico, Australia, Hungary, and South Africa (the largest producer). Some famous American mines include the Empire Mine and Red Ledge Mine in Grass Valley (Washington Co.), California. Very nice crystals and crusts have been found near Ouray, Ouray Co., and in Red Mountain Pass, San Juan Co., Colorado. The Hollinger mine, along with other mines in that area of the Porcupine District, have produced large amounts of Gold. | ||
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Picture Icon Links |
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Picture Links | 1. Roasted Gold |
