Under these two factors, nine metallic chemical elements qualify as precious metals. These are, in no particular order, gold, palladium, silver, rhodium, iridium, ruthenium, platinum, osmium, and rhenium. 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. 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". 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. Three Methods Of Assay For Raw Precious Metals Items of jewelry or art made of precious metals are hallmarked based on specific requirements either of the country of import or the place of manufacture. Such items, particularly those made of silver, gold, or platinum, are struck with an official mark (or series of marks), which guarantees fineness or purity of the metal used. As numismatic items, gold and silver coins are made almost entirely of the precious metals, respectively. Current collectible gold coins (the 22-carat gold coins), for example, are made of 92% gold, with silver and copper comprising the rest. The coins in circulation in the United States prior to 1933 were made of 90% gold and 10% copper-silver combined. Rhenium resources are identified in several countries, which include Chile, Peru, Armenia, Mexico, Russia, Canada, Kazakhstan, and Uzbekistan. The estimated total resource from these eight countries is 6,000 tonnes (6 million kilograms). The United States alone, on the other hand, has an estimated total resource of 5,000 tonnes (5 million kilograms).