Platinum is the heaviest of the precious metals. Platinum is a family group of six metals: platinum, palladium, rhodium, ruthenium, iridium, and osmium.  Like gold and silver, platinum is considered a "noble metal," which means that it will not oxidize or corrode. Unlike gold and silver, platinum in its pure state is extremely strong and durable and doesn't need to be alloyed. It will not wear down over the years or tarnish, as gold and silver can. When platinum is scratched, it does not lose material to the extent that other precious metals do.Like the diamond, platinum is rare. 10 tons of ore are needed to produce every ounce of platinum, and processing the metal into jeweler's quality platinum takes five months. In the United States, all platinum jewelry is either 90% platinum and 10% iridium or 95% platinum and 5% ruthenium. It is always stamped "IRIDIPLAT," "900pt," or "pt 900" when it is 90% platinum and "PLAT," "950pt" or "pt950" when it is at least 95% platinum.