Pyrite

The mineral pyrite, also known as fool's gold, is the most abundant sulfide mineral. Pyrite's metallic luster and pale brass-yellow hue give it a superficial resemblance to gold, hence the well-known nickname of fool's gold. The color has also led to the nicknames brass, brazzle and Brazil, primarily used to refer to pyrite found in coal. The name pyrite is derived from the Greek πυρίτης λίθος (pyritēs lithos), "stone or mineral which strikes fire." FeS2