: a malleable ductile yellow metallic element that occurs chiefly free or in a few minerals and is used especially in coins, jewelry, and dentures and in the form of its salts (as gold sodium thiomalate) especially in the treatment of rheumatoid arthritis—symbol Au; see element table
Metallic chemical element, one of the transition elements, chemical symbol Au, atomic number 79. It is a dense, lustrous, yellow, malleable precious metal, so durable that it is virtually indestructible, often found uncombined in nature. Jewelry and other decorative objects have been crafted from gold for thousands of years. It has been used for coins, to back paper currencies, and as a reserve asset. Gold is widely distributed in all igneous rocks, usually pure but in low concentrations; its recovery from ores and deposits has been a major preoccupation since ancient times (seecyanide process). The world's gold supply has seen three great leaps, with Christopher Columbus's arrival in the Americas in 1492, with discoveries in California (seegold rush) and Australia (1850–75), and discoveries in Alaska, Yukon (seeKlondike), and South Africa (1890–1915). Pure gold is too soft for prolonged handling; it is usually used in alloys with silver, copper, and other metals. In addition to being used in jewelry and as currency, gold is used in electrical contacts and circuits, as a reflective layer in space applications and on building windows, and in filling and replacing teeth. Dental alloys are about 75% gold, 10% silver. In jewelry, its purity is expressed in 24ths, or karats: 24-karat is pure, 12-karat is 50% gold, etc. Its compounds, in which it has valence 1 or 3, are used mainly in plating and other decorative processes; a soluble chloride compound has been used to treat rheumatoid arthritis.