py·rite 
(pīrīt′)
(pīrīt′)n.
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.
[Middle English perides, pirite, from Old French pirite, from Latin pyrītēs, flint; see PYRITES.]
py·ritic (-rĭtĭk), py·riti·cal (-ĭ-kəl) adj.