Oxo-mangani-leakeite from the Hoskins mine, New South Wales, Australia: occurrence and mineral description

摘要

Oxo-mangano-leakeite, a newly approved end-member of the amphibole supergroup (IMA-CNMNC 2015-035), has been found in a rock containing manganese silicate and oxide at the Hoskins Mine, a Mn deposit 3 km west of Grenfell, New South Wales. The end-member formula of oxo-mangani-leakeite is (NaNa2)-Na-A-Na-B (C)(Mn43+Li) Si-T(8) O-22 O-W(2), which would require SiO2 53.15, Mn2O3 34.91, Li2O 1.66, Na2O 10.28, total 100.00 wt.%. The empirical formula derived for the sample of this work from electron and ion microprobe analysis using constraints resulting from single-crystal structure refinement is (A)(Na0.65K0.36)(Sigma) (=) (1.01) (B)(Na-1.94 Ca-0.06)(Sigma) (=) (2.00) (C)(Mg1.60Zn0.01Mn2.323+ Fe-0.44 3+Al0.03Ti0.034+ Li-0.58)(Sigma) (=) (5.01) (T)(Si7.98Al0.02)(Sigma) (=) O-8.00(22)W(O1.34OH0.66)(Sigma) = (2.00). Oxo-mangano-leakeite is biaxial (-), with alpha = 1.681, beta = 1.712, gamma = 1.738, all +/- 0.002, and 2V (meas.) = 81.0(4)degrees, 2V (calc.) = 83.5 degrees. The unit-cell dimensions are a = 9.875(5), b = 17.873(9), c = 5.295(2) angstrom, beta = 104.74(3)degrees, V = 903.8 (7) angstrom(3); the space group is C2/m, with Z = 2. The strongest ten reflections in the powder X-ray pattern [d values (in angstrom), I, (hkl)] are: 8.423, 100, (110); 3.377, 46, (131); 4.461, 40, (040); 4.451, 40, (021); 3.134, 37, (310); 2.694, 37, (151); 2.282, 27, ((3) over bar 12); 2.734, 25, ((3) over bar 31); 2.575, 24, (061); 2.331, 24, [((3) over bar 51) ((4) over bar 21)]. The holotype material is deposited in the Canadian Museum of Nature, Ottawa, under the catalogue number CMNMC 86895.