Precious metal ores

Gold, silver, platinum, iridium, osmium, palladium, rhodium, ruthenium – these are the elements that belong to the group of noble metals, and they received their name for their extraordinary chemical resistance.

For example, gold does not oxidize even in a molten state (at T = 1064 degrees), moreover, the most caustic alkalis do not affect gold, and only "aqua regia" (a mixture of hydrochloric and nitric acid 3:1) is capable of dissolving it. Let's consider how the extraction of metals of this group occurs:

Gold.

The average gold content in the lithosphere is 4.3 10 -7 % by weight. The main methods include washing river sand (since gold is always found in native form, which is a consequence of its high chemical stability), as well as mining gold-bearing ores in mines. The main gold-mining countries are: China - 12.8%, Australia - 9.4%, South Africa - 8.9%, USA - 8.9%, Russia - 7.9%, Peru - 7.7%, Uzbekistan - 6.3%. In 2010, 2652 million tons of gold were mined in the world. And every year, world gold mining is growing.

Silver.

The silver content in the earth's crust is approximately 70 mg per ton. It is less common in native form, and is often found in deposits with other minerals. Silver is mainly extracted from gold, silver, copper, and lead-zinc ores as a by-product, but silver extraction is not always economically viable or practical. Seawater is also a promising source of silver mining, as the silver content in seawater is significantly higher than in the earth's crust. The most significant silver reserves are concentrated in Peru - 120,000 tons.

Platinum.

Platinum is one of the rarest metals, its content in the earth's crust is 5 10 -7 % by weight. The main part of platinum deposits (about 90%) is located in five countries: South Africa, the USA, Russia, Zimbabwe, China. Platinum is also extracted from ore as a secondary component, using similar methods as for gold extraction (cyanidation, almagation, etc.)

Iridium.

The content of iridium in the earth's crust is negligible, it is much less common than gold and platinum. It occurs together with rhodium, rhenium, ruthenium. Iridium is very often found in meteorites. The main deposits of iridium are located in peridotite serpentinites of folded areas (South Africa, Canada, Russia, USA, New Guinea). The annual world production of iridium is 3 tons.

Osmium.

It takes a lot of effort to extract this metal from ore. Native osmium does not occur in nature. In ores, osmium is always paired with noble rhodium. Osmium is very often found in copper, molybdenum and nickel ores. The main osmium deposits are located in southern Africa, Tasmania, Australia, the USA, Canada and Russia.

Palladium.

Palladium is also extracted as a secondary component from copper-nickel, chromium and other ores. The undisputed world leader in palladium mining is the Russian concern JSC GMAK Norilsk Nickel, about 40% of the world's palladium production. The company also mines ore on the Kola Peninsula in the Murmansk Region. The second most important world source of palladium is the Bushveld complex in South Africa. This unique deposit also provides about 40% of the world's palladium production and is the world's largest in terms of reserves of platinum group metals.

Ruthenium.

Ruthenium is obtained as a "waste" during the refining of platinum and platinum metals. A significant source of ruthenium for its extraction is its separation from fission fragments of nuclear materials (plutonium, uranium, thorium), where its content in spent fuel assemblies reaches 250 grams per ton of "burned" nuclear fuel.