Except for gold and silver (the two coinage metals), the rest of the precious metals have recorded discoveries. In the following list, the names of the discoverers and name etymologies of the seven precious metals (again, those with recorded discoveries) are provided. The year of discovery of each of these elements, as presented here, refers to the year when the element was first identified as the pure element. The precious metal is also found - alloyed with the other metals in the platinum group as well as with gold - in Ethiopia, Australia, North and South America, and in the Ural Mountains in Russia. The Norilsk Nickel Mining and Metallurgical Company in northern Russia is the largest single producer of palladium in the world. Platinum: Most Widely Traded Of The Platinum Group Metals In the periodic table of the chemical elements, six metallic elements - all transition metals - are clustered together and lie in the d-block (the d-block in the periodic table refers to groups 8, 9, and 10, periods 5 and 6). These six elements are collectively referred to as the platinum group metals. Sluice Box: This method uses the same principle as that in gold panning, only on a larger scale. In this method, a short sluice box is used. The box is constructed with barriers along its bottom, so that the gold particles are trapped as all materials are washed by water. The sluice box method is best suited for excavation in which certain implements, such as shovels, are used to feed ore into the box. Mexican Centenario, Libertad, and Onza 6. Polish Orzel bielik 7. South African Krugerrand 8. Swiss Vreneli 9. British Britannia and Sovereign 10. American Buffalo, American Eagle, and Double Eagle The 10,000-dollar Australian Gold Nugget is one of the world's largest bullion coins. Minted by the Australian government, this bullion coin is made of 1 kilogram of 99.9% pure gold. So that while the chemical element tellurium is considered one of the rarest element in the Earth's crust (its mass abundance being the same as that of rhodium, iridium, and ruthenium), its estimated price is only less than 5 U.S. dollars per troy ounce, and, therefore, cannot be considered a precious metal.