Tellurium

Franz-Joseph Müller von Reichenstein found tellurium in Transylvanian gold ore in 1782 and Klaproth named it after tellus, the earth. It is one of the rarest elements in the crust, around 1 part per billion, rarer than platinum — but it is not rare in the universe. The likely explanation is that during Earth's formation tellurium formed volatile hydrogen telluride and was lost to space, unlike its neighbours. It has a memorable occupational hazard: exposure to a few micrograms produces dimethyl telluride in the breath and sweat, and the resulting garlic odour is powerful, socially disastrous and can persist for weeks. Its two real uses are cadmium telluride thin-film photovoltaics, the main commercial rival to silicon panels, and bismuth telluride, the semiconductor in every Peltier cooler and thermoelectric generator.