Cementite

Cementite or iron carbide has the formula Fe₃C. It is a hard, brittle component of carbon steel, with orthorhombic crystals, and forms from austenite during cooling. It mixes with ferrite, the other product of austenite, to form a lamellar structure called pearlite.

Fe₃C is also known as cohenite, particularly when found mixed with nickel and cobalt carbides in meteorites. This form, a hard, shiny silver mineral, was first described by E. Weinschenk in 1889.