The Probert Encyclopaedia of Rocks & Minerals

FAHLERZ

Fahlerz or gray copper ore, is of a steel-gray or iron-black colour mineral that occurs crystallized in the form of the tetrahedron and also massive and disseminated. Its fracture is uneven or imperfectly conchoidal. It consists of from 30 to 40 per cent of copper with iron and sulphur;
but it also contains in very variable proportions zinc, lead, antimony, and silver.
Research Fahlerz