It is generally accepted that gold is one of the rarest and most expensive precious metals. This is certainly true, but another metal clearly ranks higher in both categories: rhodium.
The most expensive metal in the world today is rhodium. It is a rare metal from the platinum family that does not react with oxygen. As a result, it is resistant to corrosion and oxidation. It also has a very high melting point, around 1,964 degrees Celsius. Rhodium is used primarily in vehicle exhaust catalysis to reduce pollutant emissions. It is also used in other areas such as jewelry and storage devices. Its scarcity and high demand make it a very expensive metal.
Rhodium was discovered in 1803 by the British chemist William Hyde Wollaston, a highly respected scientist of his time, who was also responsible for the discovery of palladium a few years earlier, in 1802. While examining a sample of a platinum mineral, Wollaston noticed the presence of a silvery white metal that did not match any of the other platinum group metals known at the time. He named the new metal “rhodium,” after the Greek word “rhodon,” meaning “rose,” because of the pink color the metal imparts to a solution of rhodium sulfate.
Rhodium is found in the earth’s crust at about 0.000037 parts per million. For comparison, gold, according to the Royal Society of Chemistry, contains about 0.0013 parts per million. The metal is mainly mined in South Africa, which is the world’s largest producer. Other rhodium producing countries include Russia, Canada and the US, but their production is much lower.
Rhodium is usually mined as a by-product from the mining of platinum and other platinum group metals, as these metals often occur together in the same deposits. It is mined mainly underground. About sixteen tons of metal are mined annually (the estimated reserve is 3,000 tons).
Source: “New Science”