Silver mining is the extraction of silver from the Earth's crust. Silver is found in native form very rarely as nuggets, but more usually combined with sulfur, arsenic, antimony, or chlorine and in various ores such as argentite (Ag2S), chlorargyrite ("horn silver," AgCl), and galena (a lead ore often containing significant amounts of silver). As silver is often found in conjunction with these or alloyed with other metals such as gold, it usually must be further extracted through amalgamation or electrolysis. Silver mining has been undertaken since early times. As silver is a precious metal often used for coins, its mining has historically often been lucrative. As with other precious metals such as gold or platinum, newly discovered deposits of silver ore have sparked silver rushes of miners seeking their fortunes.