Abstract
Gold in nature is most often found in the form of native metal, intermetallic compounds and minerals containing gold, silver, copper, iron, mercury, bismuth, platinum, palladium, iridium, rhodium, and minerals -gold gellurides.In addition, gold is found in the form of compounds with organic acids.Native gold is never chemically pure and contains up to 50% impurities.The presence of impurities in gold dramatically affects its quality and properties.For example, arsenic, lead, platinum, cadmium, bismuth, tellurium give gold brittleness, which leads to overgrinding and sludging of gold in the processes of ore preparation.In addition, native gold grains can be coated with films ("shirts") of iron oxides and rock minerals, which significantly complicates the extraction of gold during amalgamation and cyanidation.Native gold has a high density -from 15.5 to 19.7 t/m 3 .Gold minerals also have high density.Depending on the size, native gold is classified into coarse (more than 2 mm), fine (0.05-2 mm), pulverized (5-50 microns) and finely divided (less than 5 microns).The behavior of native gold grains and gold-bearing minerals in the enrichment processes depends on their composition and dissemination [1].Gold closely associated with sulphides is well extracted using processes designed to extract sulphides (flotation, depositing, concentration on tables, etc.).Isolation of gold from sulfide products is usually carried out after the destruction of the sulfides themselves by calcination or biochemical method [1].Schemes and processing regimes of ores substantially depend on the mineral composition of ores, their degradability, the presence or absence of impurities that complicate the extraction of gold, and also on the particle size of gold.These and some other properties of ores are mainly determined by their origin, according to which gold ore deposits are divided into two main groups -primary and placer.About 75% of gold is mined from primary deposits, and 25% from alluvial deposits.[1]