Gold jewelry is typically made of an alloy of gold, the purity of which is stated in karats and typically has a hallmark stamped on the jewellery.
Gold is a highly sought-after precious metal which, for many centuries, has been used as money, a store of value and in jewelry. The metal occurs as nuggets or grains in rocks, underground "veins" and in alluvial deposits. It is one of the coinage metals. Gold is dense, soft, shiny and the most malleable and ductile of the known metals. Pure gold has a bright yellow color traditionally considered attractive.
Gold is the most malleable and ductile metal; a single gram can be beaten into a sheet of one square meter, or an ounce into 300 square feet. Gold leaf can be beaten thin enough to become translucent. Gold readily forms alloys with many other metals. These alloys can be produced to increase the hardness or to create exotic colors. Native gold contains usually eight to ten percent silver, but often much more.
Because of the softness of pure (24k) gold, it is usually alloyed with base metals for use in jewelry, altering its hardness and ductility, melting point, color and other properties. Alloys with lower "k", typically 22k, 18k, 14k or 10k, contain higher percentages of copper, silver or other base metals in the alloy. Copper is the most commonly used base metal, yielding a redder metal. Eighteen karat gold containing 25% copper is the most common form of rose gold.
Many objects are marked 14 karat, but were fabricated prior to 1982 when it was legal to mark items 14K, but in reality the gold is 13.5K.
Gold nuggets are naturally occurring pieces of native gold. They are never pure 24K in composition but rather about 20 to 22K (about 83% to 92%). Nuggets are also referred to by their "fineness", for example "865 fine" means the nugget is 865 parts per thousand gold. Common impurities are silver and copper. Sometimes they are mostly quartz.
White gold alloys can be made with palladium or nickel. White 18 karat gold containing 17.3% nickel, 5.5% zinc and 2.2% copper is silver in appearance. Nickel is toxic, however, and its release from nickel white gold is controlled by legislation in Europe. Alternative white gold alloys are available based on palladium, silver and other white metals (World Gold Council), but the palladium alloys are more expensive than those using nickel.
Source: Gold. (2008, January 16). In Wikipedia, The Free Encyclopedia. Retrieved 20:36, January 17, 2008, from http://en.wikipedia.org/wiki/Gold