Carbide
A carbide is a mineral made of a metal or silicon bonded to carbon, such as cohenite in iron meteorites.
A carbide is a compound in which carbon is joined directly to a metal or to silicon, with no oxygen. Carbides are rare in Earth's rocks because carbon on the surface of our planet usually combines with oxygen to make carbon dioxide or carbonate minerals.
Meteorites offer better conditions. In iron meteorites, especially some of the IAB group such as Canyon Diablo, carbon combined with iron and nickel to form cohenite and haxonite, which grow as tough, elongated crystals in the metal. In primitive chondrites, tiny presolar grains of silicon carbide, known as moissanite, survive from stars that died before the Sun was born. A titanium carbide and other exotic carbides have also been found.
Carbides need a low-oxygen, carbon-rich environment, so they are clues to the chemistry of the metal from which they grew. Cohenite slowly breaks down to graphite and iron if heated for long periods.
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