 Occurrence
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| With an abundance in the Earth's crust similar to platinum, tellurium is, apart from the precious metals, the rarest stable solid element in the earth's crust. Its abundance by mass
is less than 0.001 ppm. By comparison, even the rarest of the lanthanoids have crustal abundances of 0.5 ppm, tin and caesium
have abundances of 2 ppm, and barium of 400 ppm.
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| The extreme rarity of tellurium in the Earth's crust is not a reflection of its cosmic abundance, which is in fact greater
than that of rubidium, even though rubidium is ten thousand times more abundant in the Earth's crust. Rather, the extraordinarily low abundance of tellurium on Earth
results from the fact that, during the formation of the Earth, the stable form of elements in the absence of oxygen and water was controlled by the oxidation and reduction of hydrogen. Under this scenario elements such as tellurium which form volatile hydrides were severely depleted during the formation
of the Earth's crust through evaporation. Tellurium and selenium are the heavy elements most depleted in the Earth's crust
by this process.
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| Tellurium is sometimes found in its native (elemental) form, but is more often found as the tellurides of gold (calaverite, krennerite, petzite, sylvanite, and others). Tellurium compounds are the only chemical compounds of gold found in nature, but tellurium itself (unlike gold) is also found combined with other elements (in metallic salts). The principal source of tellurium is from anode sludges produced during the electrolytic refining of blister copper. It is a component of dusts from blast furnace refining
of lead. Tellurium is produced mainly in the US, Canada, Peru, and Japan.
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| Commercial-grade tellurium is usually marketed as minus 200-mesh powder but is also available as slabs, ingots, sticks, or
lumps. The year-end price for tellurium in 2000 was US$ 14 per pound.
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