Pyrite

Widely known as fool's gold, pyrite is the most common sulfide mineral, an iron sulfide (FeS2) whose metallic luster and pale brass-yellow color give it a superficial resemblance to gold. It crystallizes in the cubic system as cubes, pyritohedra, or octahedra and shows a greenish-black to brownish-black streak, indistinct cleavage, and a Mohs hardness of 6 to 6.5. Its specific gravity ranges from 4.95 to 5.10. Pyrite occurs in all rock types and serves as a significant source of both iron and sulfur, the latter recovered for sulfuric acid production. Unlike true gold, it is brittle, hard enough to scratch glass, and shows a dark streak that betrays its identity.

Known as 'fool's gold,' pyrite is the most common sulfide mineral. Its metallic luster and pale brass-yellow color give it a superficial resemblance to gold. Pyrite occurs in all rock types and is a significant source of iron and sulfur.