 Occurrence
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| Rhenium is not found free in nature, and it was only recently that the first rhenium mineral was found. In 1994, Nature published
a letter describing a rhenium sulfide mineral found condensing from a fumarole on Russia's Kudriavy volcano. This is not an economically viable source of the element. Rhenium is widely spread through the Earth's
crust at approximately 1 ppb.
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| Commercial rhenium is extracted from molybdenum roaster-flue gas obtained from copper-sulfide ores. Some molybdenum ores contain 0.002% to 0.2% rhenium. Total world production is between 40 and 50 tons/year; the main producers are in Chile, USA and Kazakhstan. Recycling of used Pt-Re catalyst and special alloys allow the recovery of another 10 tons/year.
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| The metal form is prepared by reducing ammonium perrhenate (NH4ReO4) with hydrogen at high temperatures.
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