The tetrahedrite group. Nomenclature and classification
The classification of the tetrahedrite group minerals in keeping with the current IMA-accepted nomenclature rules is discussed. Tetrahedrite isotypes are cubic, with space group symmetry I 4 ̄ 3m. $Ioverline43m.$The general structural formula of minerals belonging to this group can be written as M(2)A6M(1)(B4C2)X(3) D4S(1)Y12S(2)Z, where A = Cu+, Ag+, o (vacancy), and (Ag6)4+ clusters; B = Cu+, and Ag+; C = Zn2+, Fe2+, Hg2+, Cd2+, Mn2+, Cu2+, Cu+, and Fe3+; D = Sb3+, As3+, Bi3+, and Te4+; Y = S2- and Se2-; and Z = S2-, Se2-, and o.