Tellurium

Tellurium was discovered in 1782 by the Austrian mineralogist Franz-Joseph Muller von Reichenstein, in gold ores from Transylvania; it was named in 1798 by Martin Heinrich Klaproth, who confirmed it as a new element. The name comes from the Latin tellus, the Earth. Tellurium is a brittle, silvery-white metalloid, chemically akin to selenium and sulfur, used in alloys and in thermoelectric and solar-cell materials. Rare in the crust and recovered mainly from the refining of copper, tellurium is added to steel and copper to make them easier to machine, and its compounds are important in thermoelectric devices that turn heat into electricity and in cadmium-telluride thin-film solar panels.

Muller von Reichenstein was genuinely puzzled by his find, calling it metallum problematicum, the problem metal, and sending samples to the Swedish chemist Torbern Bergman for a definitive analysis; Bergman died before completing the work, and the element went unconfirmed and unnamed for a further sixteen years until Klaproth, working independently, verified it as a true new element in 1798 and gave it the name that stuck. The unusually long gap between discovery and confirmed naming makes tellurium one of the more protracted identification stories among the pre-twentieth-century elements.

Klaproth named tellurium after Tellus, the Roman personification of the Earth, in a spirit of cosmic nomenclature that runs through his work; he had also named uranium for the planet Uranus and titanium for the Titans. The choice acquired a companion when, in 1817, Berzelius named the closely related selenium after Selene, the Moon, deliberately setting the two elements as Earth and Moon side by side. Tellurium thus anchors one of the periodic table's small celestial pairings. A curious human footnote attends it: those who work with tellurium develop tellurium breath, a persistent and powerful garlic odour, from the traces the body converts and exhales, a memorable if unglamorous mark of the earth-named element.

Tellurium ranks among the rarest of the stable elements in Earth's crust, scarcer than platinum, and much of what exists occurs bound up with gold in minerals such as calaverite and sylvanite, gold tellurides that were mined during nineteenth-century rushes in Colorado and Australia, notably around what became the town of Telluride, Colorado, which took its name from the element even though little tellurium was ever actually extracted there, the name reportedly chosen in hopeful anticipation rather than established fact.