Eight metals are deemed precious: Silver, gold, and six platinum metals, including platinum, palladium, rhodium, ruthenium, iridium, and osmium.
Silver is too soft in its pure state for use in jewelry, and must be alloyed with other metals (typically copper). Silver has the highest thermal and electrical conductivity of all the metals.
Silver containing 80 percent silver and 10 percent copper or other metal.
95.0 silver contains 95 percent silver and 5 percent copper or other metal.
925 Sterling silver
Sterling silver contains 92.5 percent silver and 7.6 percent copper or other metal (a universally accepted standard, originally decreed in 1300 by England's King Edward the First).
Pure gold, like silver, is too soft for most jewelry. Therefore, it is usually blended with silver or copper to achieve a more resilient alloy. Karat (abbreviated "k" or "kt") refers to the percentage of pure gold the alloy contains (as opposed to carat weight, used for measuring precious gems, with one "c" or "cr" equaling 200 milligrams). The higher the percentage of gold contained in an item of jewelry, the higher the karat weight, with 100 percent pure gold measuring 24k, and 50 percent gold alloy measuring 12k.
"Solid gold" refers to an alloy that contains at least 10k of gold, and is not hollow. "Gold plated" items have been coated with gold of at least 10k. "Gold filled" actually also refers to items with a coating of 10k or greater gold, but in gold filled, the gold is mechanically bonded to the base metal, in a more durable fashion than simple gold plate.
White gold is an alloy of gold and nickel, sometimes also containing palladium or zinc. These metals lend the gold a pale, platinum-like color (whereas copper and silver enhance gold's natural golden hue).
The alloy of gold and metals containing iron results in gold with a bluish tinge.
Rarer and pricier than gold, platinum is the finest of the precious metals. It is a silver-white metal found worldwide, typically strengthened with other metals, such as iridium, osmium, or nickel, for use in jewelry. Platinum is not measured in karats, but rather is stamped with a standardized platinum quality mark by its manufacturer, indicating the percentage of platinum contained (Pt1000 denotes pure platinum).