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Gold in nature mostly exists in the form of a single substance, with a small amount of metal compounds, such as selenium, tellurium, antimony, etc., and rare metal compounds, such as gold-silver paste, copper-gold ore, etc., and there should be no non-metallic compounds. Gold mines are mainly classified, and various scientific research institutions form different systems according to their good research methods, but intuitively, we usually divide them into placer gold mines and rock gold mines.
Placer gold deposits are essentially gold deposits formed by long-term water erosion and downstream wind erosion deposits in some large gold mines. Depending on the region, it can be divided into gravity sand, flowing water sand, glacial sand and coastal sand. The beneficiation of placer gold is mainly gravity separation and enrichment. Most of the gold sand in China is in flake form, or because of the long history of sand mining, the rest is in flake-like fine particles. The placer gold mine that is easy to select should have more sand and less mud, with coarse sand and fine gold, otherwise it will be considered difficult to select.
Water guns and sand mining boats are commonly used for sand mining. Due to low cost and large scale, boundary grades are usually not required. Generally, it can be mined when the industrial grade reaches 0.1g/t (0.15g/m3), and placer gold ore with 0.3g/t is already a rich ore. Placer gold mining is inseparable from boiling water. Whether water can be recovered is the main factor affecting the cost of placer gold mining.
From the perspective of geological reasons, rock gold can be roughly divided into three categories: igneous rock, sedimentary rock and metamorphic rock. The gold grade in igneous rock decreases with the acidity of the rock. The highest content is dunite and peridotite, followed by diorite, and basalt is the lowest grade. However, it is known that the higher the basic properties of a rock, the more susceptible it is to oxidation and weathering. Therefore, it is reasonable for people to say that what is easy is easy to endure but hard to endure.
Generally speaking, rock gold deposits can be divided into quartz vein type, fracture zone altered rock type, veinlet disseminated type and quartz calcite type from the perspective of mineral processing.
Quartz vein type gold-bearing ores are mainly composed of pyrite, and gold ore is mainly stored between the cracks between gangue and pyrite or other metal ores. Most quartz vein-type gold ores are easy-to-select gold ores, and higher recovery rates can be obtained through heavy floatation or single floatation.
The gangue of the altered gold deposit in the fracture zone is mainly quartz and silk mica, and the metallic mineral is mainly pyrite, which is disseminated in fine veins. Gold and sulfide ores are symbiotic. The wall rock alteration is mainly composed of silicification, kaolin, silk mica and carbon. Mainly salts. In addition to pyrite, sulfide ores are easily accompanied by chalcopyrite, galena, sphalerite, etc. Deposits of this type are usually easy to select and, with a single flotation, higher recoveries can be obtained. If weathering is severe, the tailings can be secondary recovered through full mud cyanidation.
Vein disseminated gold deposits are relatively complex, and their most obvious feature is the disseminated output of gold minerals. The metal minerals are complex, including pyrite, arsenic sand, chalcopyrite, galena, magnetic pyrite, stibnite, etc. Most of the arsenic refractory minerals we often talk about belong to this type. Due to the form in which gold occurs and its subtleties, this mineral is difficult to obtain better recovery indicators through a single flotation process.
The gangue minerals of quartz-calcite gold deposits are quartz and calcite. The gold minerals are soaked in the gangue and metal minerals. The metal minerals range from simple to complex, and most of them contain toxic sand, realgar, magnetic pyrite, black copper ore, etc. Due to the gold The distribution is very good, and metallic minerals have a greater impact on the mineral selection process, so it is difficult to obtain good mineral selection indicators through a single process.
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