Pyrite

FeS₂ - Mohs Hardness: 6-6½. The name pyrite comes from pyrite lithos, which, in Greek, means \u27stone which strikes fire\u27 in reference to the tendency of the mineral to spark when struck against steel. In fact, pyrite was used for that purpose in early flintlock rifles. Pyrite has a nickname that has become famous - \u22Fool\u27s Gold\u22. The mineral\u27s gold color, metallic luster, and high specific gravity often cause it to be mistaken for gold by inexperienced prospectors.http://utdr.utoledo.edu/rock-mineral/1038/thumbnail.jp