Troilite

Troilite is an iron sulfide mineral with the composition FeS, found chiefly in meteorites. It contains iron and sulfur in nearly equal proportions.

Iron sulfide: A compound composed of iron and sulfur, occurring in several mineral forms and chemical proportions. Troilite is the near-equimolar FeS mineral within this broader chemical family.
Sulfidation: A chemical process in which sulfur reacts with a material to form sulfides. Sulfidation can produce iron sulfide where sulfur-bearing material reacts with metallic iron.
Meteorite: A natural solid object from space that survives passage through an atmosphere and reaches a planetary surface. Meteorites are the principal natural setting in which troilite is encountered.
Domenico Troili: An eighteenth-century Italian naturalist who described a meteorite fall at Albareto in 1766. The mineral was named for Troili, whose account included the material later recognized as troilite.
Stoichiometry: The quantitative relationship between elements in a chemical compound or reactants in a reaction. Troilite’s FeS formula expresses its nearly one-to-one iron-to-sulfur ratio.
Iron–sulfur system: The set of phases and reactions formed by iron and sulfur at different compositions and temperatures. Its phase relations help explain when FeS crystallizes and how it changes with heating.
Chondrite: A stony meteorite containing rounded silicate inclusions called chondrules. Troilite occurs among the metal and sulfide grains in many chondrites.
Albareto meteorite: A meteorite that fell near Albareto, Italy, in 1766 and was described by Domenico Troili. Its reported sulfide material is central to the mineral’s naming history.
Crystal structure: The ordered, repeating arrangement of atoms in a crystalline solid. Troilite’s mineral identity includes an ordered atomic arrangement, not just an FeS formula.
Troilite–pyrrhotite transition: The temperature-dependent structural change between troilite and high-temperature iron-deficient sulfide phases. Heating can transform troilite’s low-temperature structure into a pyrrhotite-related form.

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Iron(II) sulfideBroader topic: It is the naturally occurring mineral form identified with FeS.