Bismuth is named from the German Weisse Masse, white mass and discovered in 1753. It is a white, crystalline, brittle metal that occurs native. The most important ores are bismuthinite and bismite. Peru, Japan, Mexico, Bolivia and Canada are major bismuth producers. Much of the bismuth produced in the U.S. is obtained as a by-product in refining lead, copper, tin, silver and gold ores. Bismuth is the most diamagnetic of all metals and has very low thermal conductivity. With other metals, such as tin or cadmium, bismuth forms low melting alloys which are extensively used in fire detection and extinguishing systems.