a hard, brittle, yellow mineral, FeS, dimorphic with marcasite and occurring abundantly as a native ore, used to make sulfuric acid; iron sulfide
See pyrite in American Heritage Dictionary 4
(pīˈrītˌ)
noun
A brass-colored mineral, FeS2, occurring widely and used as an iron ore and in producing sulfur dioxide for sulfuric acid. Also called fool's gold, iron pyrites.