GOLD
gold - mineral 1.1.1.1
| Chemical Formula | Au | |||
| Composition | Gold, with small amounts of silver; sometimes also copper and iron | |||
| Variable Formula | (Au,Ag) ; (Au,Ag,Cu,Fe) |
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| Color | Golden yellow to brass yellow | |||
| Streak | Golden yellow | |||
| Hardness | 2½ - 3 | |||
| Crystal Forms and Aggregates |
(Isometric) Dendrites, wires, nuggets, encrustations, and small flakes are the common forms. Octahedral, dodecahedral, and cubic crystals also occur, but they are uncommon and are often distorted. Crystals usually have some level of hopper growth. | |||
| 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 | |||
| Other Names | ||||
| Varieties | ||||
| In Group | Native elements ; Metallic elements | |||
| All About | 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 (SG) 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. |
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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. 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 mearued 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. Also see the gemstone section on Gold. |
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| Striking Features | Golden-yellow color, extreme heaviness, lack of tarnish, and malleability and ductility | |||
| Complex Tests | Soluble only in aqua regia | |||
| Popularity (1-4) | 1 | |||
| Prevalence (1-3) | 3 | |||
| Demand (1-3) | 1 | |||
| Distinguishing Similar Minerals |
Pyrite and Marcasite (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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| Commonly Occurs With |
Quartz, Pyrite, Arsenopyrite, Silver, Limonite | |||
| Noteworthy Localities |
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 are 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 occurences where noteworthy specimens extracted have made their way to collections. |
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| Picture Icon Links |
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| Picture Links | 1. Roasted Gold |
Additional references
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