In fact, thirteen years after its introduction, this precious metal coin accounted for about ninety percent of the gold coin market. The Krugerrand comes in four varieties: 1. One-tenth ounce coin (0.11 troy ounce in weight, 1.35 millimeters thick, and 16.55 millimeters in diameter). 2. Quarter ounce coin (0.27 troy ounce in weight, 1.89 millimeters thick, and 22.06 millimeters in diameter). A brief description of each of these precious metals is provided below. 1. Ruthenium - This element is represented by the symbol Ru. Its atomic number is 44. It is mostly found in platinum ores and often used in platinum alloys as a catalyst. Its two main physical characteristics refer to its hardness as a metal and to its silvery-white color. Because of low circulation of palladium coins, palladium as an investment commodity is not as good as either silver or gold. Another reason for this is the relatively wider spread between the metal's buying and selling prices. Palladium is traded on the London Stock Exchange as an exchange-traded fund (ETF), under the ticker symbol LSE: PHPD. The gold particles, having higher density than the other materials (examples, mud, sand and gravel; also, gold is about nineteen times heavier than water), settle to the bottom of the pan, while the lighter materials are washed over the side. Sluice Box: This method uses the same principle as that in gold panning, only on a larger scale. As catalysts for hydrogenation of fine chemicals, because of its high resistance to chemical poisoning from phosphorus, sulfur, and nitrogen. 5. As treatment for liver cancer, because of its radioactive isotopes. Rhenium resources are identified in several countries, which include Chile, Peru, Armenia, Mexico, Russia, Canada, Kazakhstan, and Uzbekistan. The ranking appears different when the estimated world market prices, per troy ounce, of these nine precious metals are considered (estimates as of January 2010): 1st: Rhodium - USD2,750 2nd: Platinum - USD1,555 3rd: Gold - USD1,131 4th: Palladium - USD424 5th: Iridium - USD408 6th: Osmium - USD380 7th: Rhenium - USD194 8th: Ruthenium - USD173 9th: Silver - USD18 Of the nine precious metals, gold and silver are the best known.