For thousands of years silver has been highly valued as a precious metal. Chemically, silver is classified as a noble metal. Noble metals are elements that tend not to be very reactive. They include, in addition to silver, gold, platinum, ruthenium, rhodium, palladium, osmium, and iridium. Although it has been regarded as less valuable than gold in most cultures, silver is better for some purposes because it is harder than gold. Silver occurs naturally and in some ores. After it is mined, silver is refined by heating it until the impurities rise to the surface, a process called smelting.
Silver was one of several metals used for making coins, medallions, and artifacts in ancient Greece, Rome, and other parts of the Mediterranean. Oval-shaped pieces of silver with no set value were used in trade until standardized coinage (coins with set values) was issued in Asia Minor by King Croesus of Lydia (595-c546 bce), once said to be the richest man in the world. His concept was so successful that silver coins appeared in Persia, India, and China soon after. The Chinese used silver coins of the same basic size and shape from approximately 500 bce to the early twentieth century.
Silver has also been used in jewelry, religious artifacts, ornaments, and tableware. It is sometimes combined with other metals such as lead or gold. It can be alloyed (mixed) with copper to make sterling silver. The copper adds strength so coins, silverware, and jewelry can be used for a longer time. A silver nitrate compound can be applied as silver plating, which is used in mirrors and less expensive tableware. Silver can also be worked into extremely thin paint called leaf to coat less costly metals.
About one-quarter of the world's silver is mined in North America. Peru is the world's largest supplier of silver, followed by Mexico, China, and Australia. In 2006, about forty percent of the world's silver supply was used for industrial purposes, twenty four percent for photographic applications, thirty three percent for jewelry and silverware, and about three percent for coins and metals. Many countries, including the United States, have reduced or eliminated the silver content of coins because the metal is often worth more than the face value of the money.
Silver iodide crystals are used in cloud seeding, a technique for stimulating rain by distributing the crystals through clouds. Silver iodide is used in medicine as an antiseptic. Some specialized types of batteries are from cadmium or zinc and silver.