Chalcopyrite with Byssolite

The French Creek Mine was a source for magnetite from 1845 to 1928. The dumps were opened for collecting soon after and it quickly became famous for the highly distinctive flattened disphenoids with hoppered faces in delicate parallel groups. The back is partially coated with mattes of Byssolite. This example is a true classic, Found in 1979 by Al Bullock. Ex George Loud

Locality: French Creek Mine, St Peters, Pennsylvania

Composition: copper iron sulfide