This is lower by about 77 million troy ounces when compared with the annual mine production of gold, and even much lower - by about 547 million troy ounces - when compared with the yearly silver mine production. Platinum is traded on the London Stock Exchange (as ETF, under the ticker symbol LSE: PHPT) and on the New York Mercantile Exchange. Placer Mining: Three Methods Used To Mine Placer Gold The word placer, as will be found throughout here, is derived from the same Spanish word which means "sandbank". It specifically refers to an alluvial deposit of detrital material, such as gravel, which contains particles of precious chemical elements. Ruthenium tetroxide, a yellow, diamagnetic tetrahedral ruthenium compound, is highly toxic and volatile; it may explode if it comes into contact with combustible materials. Osmium: Osmium, like iridium, can ignite spontaneously in air when in finely divided form. The compound osmium tetroxide, in particular, is highly volatile and is extremely toxic if accidentally inhaled, ingested, or comes into contact with the skin. Iridium is named after the Latin word "iris", which means "rainbow". 5. Rhodium - William Hyde Wollaston discovered rhodium in 1803, shortly after he discovered palladium. He discovered this precious metal from crude platinum samples obtained from South America. The name rhodium was derived from the Greek word "rhodon", which means "rose". Silver coins, like the minted coins circulated in the United States and other countries prior to 1965, were made of 90% silver and 10% copper. The American Silver Eagle and the Mexican Silver Libertad bullion coins, introduced in 1986 and 1982 respectively, were made of 99.9% silver and 0.1% copper. Other notable silver bullion coins include the Australian Silver Kookaburra, Chinese Silver Panda, and the Russian George the Victorious. Currency or coinage (as in silver bullion). The principal sources of silver are copper, lead, zinc and gold ores. It also occurs in the minerals chlorargyrite and argentite. Of course, silver occurs natively, too. Some of the top silver-producing countries in the world are the United States, Canada, Peru, and Mexico.