Geocronite
Geocronite is a mineral, a mixed sulfosalt containing lead, antimony, and arsenic with a formula of Pb14(Sb, As)6S23. Geocronite is the antimony rich endmember of a solid solution series. The arsenic rich endmember is named jordanite. It occurs as grey, black, to silvery white monoclinic crystals. It is found in hydrothermal veins usually associated with other similar minerals, particularly the sulfides of iron and copper.