tetrahedrite
noun
tet·ra·he·drite
plural -s
: a fine-grained gray mineral (Cu,Fe)12Sb4S13 that is isomorphous with tennantite, consists of a sulfide of copper, iron, and antimony and often also contains zinc, lead, mercury, or silver, occurs in characteristic tetrahedral crystals and also in massive form, and is often a valuable ore of silver and is also worked for copper (hardness 3–4, specific gravity 4.4–5.1)
Word History
Etymology
German tetraëdrit, from Late Greek tetraedros having four faces + German -it -ite