The content of gold in the earth's crust is very low - 0,5 ÷ 5 mg / kg [6] [7], but the field and areas dramatically enriched metal, are very numerous. Gold is found in the water. 1 liter and sea and river water is about 4.10 -9 g of gold, which corresponds to 4 kilograms of gold in a cubic kilometer of water.
Gold deposits occur mainly in the areas of granitoids, a small number associated with basic and ultrabasic rocks. Gold forms the industrial concentration in the post-magmatic, hydrothermal mainly, fields. In the exogenous conditions of visible gold is a very stable element and can easily accumulate in placers. However, submicroscopic gold, part of the sulfides, the oxidation of the latter acquires the ability to migrate in the oxidation zone. As a result, gold is sometimes stored in the zone of secondary sulphide enrichment, but the maximum concentrations associated with its accumulation in the oxidation zone, where it associates with the hydroxides of iron and manganese. The migration of gold in the oxidation zone of sulfide deposits occur in the form of methyl iodide and the compounds in ionic form. Some scientists allowed the transfer of gold dissolution and sulphate of iron oxide or as a slurry suspension.
In nature, known for 15 gold minerals: native gold alloy of silver, copper, etc., electrum and Au 25 - 45% Ag; porpesit AuPd; cuprous gold bismutoaurit (Au, Bi); rodistoe gold iridistoe gold platinistoe gold. The other minerals are tellurides of gold: calaverite AuTe2, krennerite AuTe2, sylvanite AuAgTe4, petzite Ag3AuTe2, mutmanit (Ag, Au) Te, montbreyit Au2Te3, nagyagite Pb5AuSbTe3S6.
For gold is characterized by native form. Among its other forms it is worth noting electrum, an alloy of gold and silver, which has a greenish tint and relatively easily destroyed by water transport. In the rocks of the gold is usually dispersed at the atomic level. In the fields it is often enclosed in sulfides and arsenides.
Differ in the primary gold deposits, deposits in which it falls as a result of the destruction of ore deposits and deposits with complex ores in which gold is extracted as the associated component.
