Rhenium

Rhenium is a rare, silvery-gray transition metal that stays strong at very high temperatures. It is found mainly in tiny amounts in molybdenite, a molybdenum ore, rather than in rich deposits of its own. Most rhenium is recovered as a by-product when molybdenum ores are processed: roasting releases rhenium compounds into gases and dust, from which the element can be separated and purified. Recycling also supplies some of the metal. Rhenium is added to nickel-based superalloys used in hot parts of jet engines, helping them withstand demanding conditions. It is also used with platinum in catalysts that help turn petroleum liquids into high-octane fuel. Rhenium-containing alloys are used in thermocouples and X-ray equipment, where their resistance to heat is useful.