Silver is found in native form, alloyed with gold or combined with sulfur, arsenic, antimony or chlorine in ores. Silver is a fairly rare element in the Earth’s crust. Its abundance is estimated to be about 0.1 parts per million. It is also found in seawater. Its abundance there is thought to be about 0.01 parts per million.
Silver usually occurs in association with other metal ores, especially those of lead. The most common silver ores are argentite (Ag2S); cerargyrite, or “horn silver” (AgCl); proustite (3Ag2S ? As2S3); and pyrargyrite (Ag2S ? Sb2S3). The principal sources of silver are the ores of copper, copper-nickel, lead, and lead-zinc obtained from Peru, Mexico, China, Australia, Chile and Poland.
Peru and Mexico have been mining silver since 1546 and are still major world producers. Top silver-producing mines are Proaño / Fresnillo (Mexico), Cannington (Queensland, Australia), Dukat (Russia), Uchucchacua (Peru) and Greens Creek mine (Alaska). The metal can also be produced during the electrolytic refining of copper and by the application of the Parkes process on lead metal obtained from lead ores that contain small amounts of silver.
Commercial-grade fine silver is at least 99.9% pure silver, and purities greater than 99.999% are available. In 2007, Peru was the world’s top producer of silver, closely followed by Mexico. In the United States, silver is produced at about 76 mines in 16 states. The largest state producers are Nevada, Idaho, and Arizona. These three states account for about two-thirds of all the silver mined in the United States. Ores rich in silver disappeared long ago due to mining.
Today, silver usually comes from ores that contain very small amounts of the metal. These amounts can range from about a few thousandths of an ounce per ton of ore to 100 ounces per ton. The metal is most commonly produced as a by-product of mining for other metals.