Iron pyrite, also known as "fool's gold", is a mineral that resembles gold but is actually composed of iron sulfide. There are several synonyms for this mineral, including "pyrite", "iron sulfide", "brass bronze", and "marcasite". Pyrite is a Greek word which means "firestone" due to its ability to produce sparks when struck against metal or stone. Iron sulfide is a term used in chemistry to describe the compound of iron and sulfur. Brass bronze is a term used to refer to minerals that contain both copper and iron sulfides. Marcasite, on the other hand, is a polymorph of pyrite with a unique crystal structure.