• journal_title：Mineralogical Magazine
• Contributor：A. V. Kasatkin ; F. Nestola ; J. Plášil ; J. Marty ; D. I. Belakovskiy ; A. A. Agakhanov ; S. J. Mills ; D. Pedron ; A. Lanza ; M. Favaro ; S. Bianchin ; I. S. Lykova ; V. Goliáš ; W. D. Birch
• Publisher：Mineralogical Society of Great Britain and Ireland
• Date：2013-04-01
• Format：text/html
• Language：en
• Identifier：10.1180/minmag.2013.077.3.10
• journal_abbrev：Mineralogical Magazine
• issn：0026-461X
• volume：77
• issue：3
• firstpage：367
• section：Articles

Two new minerals – manganoblödite (IMA2012–029), ideally Na₂Mn(SO₄)₂·4H₂O, and cobaltoblödite (IMA2012–059), ideally Na₂Co(SO₄)₂·4H₂O, the Mn-dominant and Co-dominant analogues of blödite, respectively, were found at the Blue Lizard mine, San Juan County, Utah, USA. They are closely associated with blödite (Mn-Co-Ni-bearing), chalcanthite, gypsum, sideronatrite, johannite, quartz and feldspar. Both new minerals occur as aggregates of anhedral grains up to 60 μm (manganoblödite) and 200 μm (cobaltoblödite) forming thin crusts covering areas up to 2×2 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 blödite. Manganoblödite and cobaltoblödite are transparent, colourless in single grains and reddish-pink in aggregates and crusts, with a white streak and vitreous lustre. Their Mohs' hardness is ~2½. 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 manganoblödite and D_meas = 2.29(2) g cm⁻³ and D_calc = 2.347 g cm⁻³ for cobaltoblödite. Optically both species are biaxial negative. The mean refractive indices are α = 1.493(2), β = 1.498(2) and γ = 1.501(2) for manganoblödite and α = 1.498(2), β = 1.503(2) and γ = 1.505(2) for cobaltoblödite. The chemical composition of manganoblödite (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.p.f.u., is: Na_1.96(Mn_0.44Mg_0.29Co_0.14Ni_0.06)_Σ0.93S_2.03O₈·4H₂O. The chemical composition of cobaltoblödite (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(Co_0.36Mg_0.30Mn_0.17Ni_0.12)_Σ0.95S_2.02O₈·4H₂O. Both minerals are monoclinic, space group P2₁/a, with a = 11.137(2), b = 8.279(1), c = 5.5381(9) Å, β = 100.42(1)°, V = 502.20(14) ų and Z = 2 (manganoblödite); and a = 11.147(1), b = 8.268(1), c = 5.5396(7) Å, β = 100.517(11)°, V = 501.97(10) ų and Z = 2 (cobaltoblödite). The strongest diffractions from X-ray powder pattern [listed as (d, Å(I)(hkl)] are for manganoblödite: 4.556(70)(210, 011); 4.266(45)(2İ01); 3.791(26)(2İ11); 3.338(21)(310); 3.291(100)(220, 021), 3.256(67)(211, 1İ21), 2.968(22)(2İ 21), 2.647(24)(4İ01); for cobaltoblödite: 4.551(80)(210, 011); 4.269(50)(2İ01); 3.795(18)(2İ11); 3.339(43)(310); 3.29(100)(220, 021), 3.258(58)(211, 1İ21), 2.644(21)(4İ01), 2.296(22)(1İ22). The crystal structures of both minerals were refined by single-crystal X-ray diffraction to R₁ = 0.0459 (manganoblödite) and R₁ = 0.0339 (cobaltoblödite).