Pyrite & Quartz Face (From Our Private Collection)A golden yellow to brown, widely occurring mineral sulfide, FeS2, Pyrite is used as an iron ore and to produce sulfur dioxide for sulfuric acid. It is also known as Fool's Gold because it resembles gold, even though it is harder (H. 5 6) and a paler yellow. Pyrite is often found in quartz veins, sometimes even with gold. Pyrite crystals are common; it may also occur as grains or in masses. It streaks a greenish black and when tarnished, may resemble