Formula: Cu31S16 Monoclinic
Description: Djurleite is a black massive mineral most often found as a supergene mineral in copper deposits. It is easily mistaken for chalcocite, hence frequently overlooked.
Heyl and others (1970, 1978) note it as occurring with chalcocite in the Upper Mississippi Valley zinc-lead district in Grant, Iowa, and Lafayette Counties, but give no locality information. A sample (NS.21977.003) in the UW–Madison Geology Museum has a black coating on pyrite from Mineral Point that was determined to be djurleite (Klaus Westphal, 1990, personal communication).