Jewelry metals include silver, gold, platinum, and a few other rare elements

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Jewelry Metals

Jewelry metals include silver, gold, platinum, and a few other rare elements; this group as a whole consists of the so-called "precious metals."

Pure gold is 24 karat; the karat designation is a measure of "fine¬ness.'' By law, gold jewelry must be stamped if above 10 karat; gold less than l OK tine cannot have a karat mark or be called "gold."

Gold-filled and plated articles consist of a metal base covered with a thin sheet of gold at least l OK fine. Gold-filled articles must be at least 1/20 by weight of gold of the quality stated, such as "1/20 12K gold filled." Colored gold is produced by alloying: copper (red), cadmium and silver (green), iron (blue), nickel or palladium (white), and aluminum or zinc (purple).

Jewelry Metals

Pure silver is taken to mean 99.99 percent silver. Most so-called "pure" silver available is less than 99.5 percent or "995 tine." Sterling silver is not less than 925 fine, or 92.5 percent silver. Coin silver is generally 900 fine, and articles less than 900 fine cannot, by law, be represented as "silver." Federal law prohibits the use of the terms "Sterling" or "coin" on plated articles.

Platinum and related metals (iridium, rhodium, osmium, palladium, and ruthenium) are used extensively in jewelry. Platinum is harder than gold and therefore more difficult to work, but better for securely holding fine gems in settings. Platinum metal alloys are designated according to composition, such as 0.600 Plat., 0.350 Pall., indicating 60 percent platinum, 35 percent palladium, and 5 percent of some other metal. Silver tends to tarnish with time, due to the formation of a black oxide coating.

This can be polished oft, but can be prevented entirely by plating a silver article with rhodium, which is bright and silvery but will not tarnish. This plating does not affect the value of the article.

A hallmark is a stamp applied by an organization to indicate the fineness of a precious metal article. Such marks are applied only after 154 assay proves that the metal meets the required standards.