Manganoblodite, Na2Mn(SO4)2•4H2O, and cobaltoblodite, Na2Co(SO4)2•4H2O: two new members of the blodite group from the Blue Lizard mine, San Juan County, Utah, USA

Two new minerals - manganoblodite (IMA2012-029), ideally Na2Mn(SO4)(2)center dot 4H(2)O, and cobaltoblodite (IMA2012-059), ideally Na2Co(SO4)(2)center dot 4H(2)O, the Mn-dominant and Co-dominant analogues of blodite, respectively, were found at the Blue Lizard mine, San Juan County, Utah, USA. They are closely associated with blodite (Mn-Co-Ni-bearing), chalcanthite, gypsum, sideronatrite, johannite, quartz and feldspar. Both new minerals occur as aggregates of anhedral grains up to 60 mu m (manganoblodite) and 200 mu m (cobaltoblodite) forming thin crusts covering areas up to 2 x 2 cm on the surface of other sulfates. Both new species often occur as intimate intergrowths with each other and also with Mn-Co-Ni-bearing blodite. Manganoblodite and cobaltoblodite are transparent, colourless in single grains and reddish-pink in aggregates and crusts, with a white streak and vitreous lustre. Their Mohs' hardness is similar to 21/2. They are brittle, have uneven fracture and no obvious parting or cleavage. The measured and calculated densities are D-meas = 2.25(2) g cm(-3) and D-calc = 2.338 g cm(-3) for manganoblodite and D-meas = 2.29(2) g cm(-3) and D-calc = 2.347 g cm(-3) for cobaltoblodite. Optically both species are biaxial negative. The mean refractive indices are alpha = 1.493(2), beta = 1.498(2) and gamma = 1.501(2) for manganoblodite and alpha = 1.498(2), beta = 1.503(2) and gamma = 1.505(2) for cobaltoblodite. The chemical composition of manganoblodite (wt.%, electron-microprobe data) is: Na2O 16.94, MgO 3.29, MnO 8.80, CoO 2.96, NiO 1.34, SO3 45.39, H2O (calc.) 20.14, total 98.86. The empirical formula, calculated on the basis of 12 O a.pf.u., is: Na-1.96(Mn0.44Mg0.29Co0.14Ni0.06)(Sigma 0.93)S2.03O8 center dot 4H(2)O. The chemical composition of cobaltoblodite (wt.%, electron-microprobe data) is: Na2O 17.00, MgO 3.42, MnO 3.38, CoO 7.52, NiO 2.53, SO3 45.41, H2O (calc.) 20.20, total 99.46. The empirical formula, calculated on the basis of 12 O a.p.f.u., is: Na-1.96(Co0.36Mg0.30Mn0.17Ni0.12)(Sigma 0.95)S2.02O8 center dot 4H(2)O; Both minerals are monoclinic, space group P2(1)/a, with a = 11.137(2), b = 8.279(1), c = 5.5381(9) angstrom, beta = 100.42(1)degrees, V = 502.20(14) angstrom(3) and Z = 2 (manganoplodite); and a = 11.147(1), b = 8.268(1), c = 5.5396(7) angstrom, beta = 100.517(11)degrees, V = 501.97(10) angstrom(3) and Z = 2 (cobaltoblodite). The strongest diffractions from X-ray powder pattern [listed as (d,angstrom(I)(hkl)] are for manganoblodite: 4.556(70)(210, 011); 4.266(45)((2) over bar 01); 3.791(26)((2) over bar 11); 3.338(21)(310); 3.291(100)(220, 021), 3.256(67)(211, (1) over bar 21), 2.968(22)((2) over bar 21), 2.647(24)((4) over bar 01); for cobaltoblodite: 4.551(80)(210, 011); 4.269(50)((2) over bar 01); 3.795(18)((2) over bar 11); 3.339(43)(310); 3.29(100)(220, 021), 3.258(58)(211, (1) over bar 21), 2.644(21)((4) over bar 01), 2.296(22)((1) over bar 22). The crystal structures of both minerals were refined by single-crystal X-ray diffraction to R-1 = 0.0459 (manganoblodite) and R-1 = 0.0339 (cobaltoblodite).