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Gold often occurs in free elemental (native state), as nuggets or grains, in rocks, veins, and alluvial deposits. It occurs in a solid solution series with the native element silver (as in electrum), naturally alloyed with other metals like copper and palladium, and mineral inclusions such as within pyrite.
Colored gold is the name given to any gold that has been treated using techniques to change its natural color. Pure gold is slightly reddish yellow in color, [1] but colored gold can come in a variety of different colors by alloying it with different elements. Colored golds can be classified in three groups: [2] Alloys with silver and copper in ...
An alloy may have a variable or fixed composition. For example, gold and silver form an alloy in which the proportions of gold or silver can be varied; titanium and silicon form an alloy TiSi 2 in which the ratio of the two components is fixed (also known as an intermetallic compound [34] [35]).
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A noble metal is ordinarily regarded as a metallic element that is generally resistant to corrosion and is usually found in nature in its raw form. Gold, platinum, and the other platinum group metals (ruthenium, rhodium, palladium, osmium, iridium) are most often so classified. Silver, copper, and mercury are sometimes included as noble metals ...
Gold compounds. Gold compounds are compounds by the element gold (Au). Although gold is the most noble of the noble metals, [1][2] it still forms many diverse compounds. The oxidation state of gold in its compounds ranges from −1 to +5, but Au (I) and Au (III) dominate its chemistry. Au (I), referred to as the aurous ion, is the most common ...
Fineness. The fineness of a precious metal object (coin, bar, jewelry, etc.) represents the weight of fine metal therein, in proportion to the total weight which includes alloying base metals and any impurities. Alloy metals are added to increase hardness and durability of coins and jewelry, alter colors, decrease the cost per weight, or avoid ...
In contrast, certain metal alloys exhibit unique properties where their size and density remain unchanged across a range of temperatures. [32] Cast iron is defined as an iron–carbon alloy with more than 2.00%, but less than 6.67% carbon. Stainless steel is defined as a regular steel alloy with greater than 10% by weight alloying content of ...