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(named for the 18th-century Italian scientist D. Troili, who described a meteorite containing the mineral), a mineral Of the sulfide group, FeS.
Troilite crystallizes in a hexagonal system, and its crystal structure resembles that of hexagonal pyrrhotite. It forms brownish yellow rounded segregations with a metallic luster; less fre quently it occurs as poorly formed crystals. In cryptocrystalline aggregates it is black. Its hardness on Mohs’ scale is 4, and its density is 4,600–4,840 kg/m3. Troilite is primarily a meteorite mineral; terrestrial troilite is rare, occurring as inclusions in native iron and in copper ores and chromites associated with ultra-basic rocks.