HUANZALAITE, MgWO4, A NEW MINERAL SPECIES FROM THE HUANZALA MINE, PERU

Huanzalaite, ideally MgWO4, occurs as inclusions in scheelite in the Huanzala mine, Peru. It forms orange to reddish brown aggregates composed of minute (<10 mu m) crystals. The average size of the aggregates is approximately 0.1 mm across. It is monoclinic, P2/c, with cell parameters a 4.7027(15), b 5.6894(11), c 4.9413(9) angstrom, beta 90.70(2)degrees, V 132.20(5) angstrom(3) and Z = 2. The strongest seven lines in the powder XRD pattern [d in (angstrom)(I/I-0)(hkl)] are: 3.73(100)(011), 2.91(94)(111), 2.93(83)(111), 4.70(74) (100), 3.63(39)(110), 2.47(39)(002) and 2.18(32)(121). The mean composition derived from ten electron-microprobe analyses contains (wt.%); WO3 84.81, MgO 12.49, MnO 1.78, FeO 1.39, with trace amounts of Ca, and lead to the empirical formula (Mg0.85Mn0.07Fe0.05) S0.97W1.01O4. Huanzalaite is a member of the wolframite group (class 4.DB of Strunz & Nickel), and is the Mg-dominant analogue of hubnerite, MnWO4, ferberite, FeWO4, and sanmartinite, ZnWO4. The calculated density of huanzalaite is 6.953 g/cm(3). Huanzalaite shows bluish fluorescence under UV light. The mineral formed during the metasomatic emplacement of the copper orebody. The source of Mg in this mineral, as well as in the associated sellaite, talc and tremolite, may be dolomite in limestone, which is the host rock of the orebody.