Other nations, such as Canada, Australia, the United States, and the United Kingdom, started producing their own precious metal coins one after the other beginning in 1979. The decisions of these gold-producing countries to mint their own bullion coins were most likely inspired by the success of the Krugerrand in its role as a vehicle for promoting the South African gold to the international market. Other countries later began issuing their own palladium bullion coins, including Canada (with its Big & Little Bear Constellations and the very popular Palladium Maple Leaf), Australia, France, China, Portugal, and the former Soviet Union. The latter, in fact, is known to have minted the most number of palladium coins in the world. The Hand of Faith Gold Nugget: This gold nugget actually carries two distinctions: "the largest gold nugget found by a metal detector" and "the largest gold nugget currently in existence". It was discovered on September 26, 1980 somewhere near the small town of Kingower in Victoria, Australia. For example, osmiridium (a natural alloy of osmium and iridium) is alloyed with the other metals in the platinum group and used in instrument pivots and phonograph needles (apart from electrical contacts and fountain pen tips as mentioned earlier). In another example, osmium tetroxide is used to detect fingerprints and to stain fatty tissue for optical and electron microscopy. 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. There are nine known precious metals - gold, platinum, iridium, palladium, osmium, silver, rhodium, ruthenium, and rhenium. With the exception of the latter, all are considered noble metals. Using the "aqua regia" test (aqua regia is a mixture of concentrated nitric acid and concentrated hydrochloric acid, which is highly corrosive), here's how the eight precious-noble metals react: Gold, platinum, palladium, and osmium dissolve.