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Eckerite, ideally Ag2CuAsS3, is a new mineral from the Lengenbach quarry in the Binn Valley, Valais, Switzerland. It occurs as very rare euhedral crystals up to 300 mm across associated with realgar, sinnerite, hatchite, trechmannite and yellow, fibrous smithite. In thick section eckerite is opaque with a metallic lustre and shows a dark orange-red streak. It is brittle; the Vickers hardness (VHN25) is 70 kg/mm2 (range: 64-78) (Mohs hardness of ~2½-3). In reflected light, eckerite is moderately bireflectant and weakly pleochroic from light grey to a slightly bluish grey. Internal reflections are absent. Under crossed nicols, it is weakly anisotropic with greyish to light blue rotation tints. Reflectance percentages for Rmin and Rmax are 27.6, 31.7 (471.1 nm), 22.8, 26.1 (548.3 nm), 21.5, 24.5 (586.6 nm) and 19.4, 22.3 (652.3 nm), respectively. Eckerite is monoclinic, space group C2/c, with a = 11.8643(3), b = 6.2338(1), c = 16.6785(4) Å , β = 110.842(3)º, V = 1152.81(5) Å3, Z = 8. The crystal structure [R1 = 0.0769 for 1606 reflections with Fo > 4σ(Fo)] is topologically identical to that of xanthoconite and pyrostilpnite. In the structure, AsS3 pyramids are joined by AgS3 triangles to form double sheets parallel to (001); the sheets are linked by Cu(Ag) atoms in a quasi-tetrahedral coordination. Among the three metals sites, Ag2 is dominated by Cu. The mean metal-S distances reflect well the Ag ↔ Cu substitution occurring at this site. The eight strongest powder X-ray diffraction lines [d in Å (I/I0) (hkl)] are: 3.336 (70) (3̅12); 2.941 (100) (3̅14,114); 2.776 (80) (400,2̅06); 2.677 (40) (312); 2.134 (50) (4̅21); 2.084 (40) (2̅08,206); 2.076 (40) (420); 1.738 (40) (2̅28,226). A mean of five electron microprobe analyses gave Ag 52.08(16), Cu 11.18(9), Pb 0.04(1), Sb 0.29(3), As 15.28(11), S 20.73(13), total 99.60 wt.%, corresponding, on the basis of a total of 7 atoms per formula unit, to Ag2.24Cu0.82As0.94Sb0.01S2.99. The new mineral has been approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification (2014-063) and named for Markus Ecker, a well known mineral expert on the Lengenbach minerals for more than 25 years. [ABSTRACT FROM AUTHOR]

Deveroite-(Ce), ideally Ce2(C2O4)3.10H2O, is a new mineral (IMA 2013-003) found in the alpine fissures of Mount Cervandone, overlooking the Devero Valley, Piedmont, Italy. It occurs as sprays of colourless elongated tabular, acicular prisms only on cervandonite-(Ce). It has a white streak, a vitreous lustre, is not fluorescent and has a hardness of 2-2.5 (Mohs' scale). The tenacity is brittle and the crystals have a perfect cleavage along {010}. The calculated density is 2.352 g/cm3. Deveroite-(Ce) is biaxial (-) with 2V of ∼77°, is not pleochroic and the extinction angle (β c) is ∼27°. No twinning was observed. Electron microprobe analyses gave the following chemical formula: (Ce1.01Nd0.33La0.32Pr0.11Y0.11Sm0.01Pb0.04U0.03Th0.01Ca0.04)2.01(C2O4)2.99.9.99H2O. Although synchrotron radiation was not used to solve the structure of deveroite-(Ce) the extremely small size of the sample (13 μm×3 μm×1 μm) did not allow us to obtain reliable structural data. However, it was possible to determine the space group (monoclinic, P21/c) and the unit-cell parameters, which are: a = 11.240(8) Å, b = 9.635(11) Å , c = 10.339(12) Å, b = 114.41(10)°, V = 1019.6 Å3. The strongest lines in the powder diffraction pattern [d in Å (I)(hkl)] are: 10.266(100)(100); 4.816(35.26)(211); 3.415(27.83)(300); 5.125(24.70)(200); and 4.988(22.98)(111). Deveroite-(Ce) is named in recognition of Devero valley and Devero Natural Park. [ABSTRACT FROM AUTHOR]

A single crystal of natrojarosite, NaFe3(SO4)2(OH)6, was investigated by single-crystal X-ray diffraction at high-pressure conditions (up to 8.8 GPa) using a diamond-anvil cell. The unit-cell parameters were determined at 11 different pressures and no indications of a phase transition were found up to the maximum pressure reached. The volume and axial moduli were fitted to a third-order Birch-Murnaghan equation-of-state which gave the following values: V0 = 769.6(2) Å3, KT0 = 50.6(9) GPa, K' = 9.9(4); a = 7.3172(6) Å, KT' = 104(2), K' = 7.6(9); c = 16.5965(20) Å, KT0 = 24.6(4) and K' = 7.1(2). The crystal structure of natrojarosite was refined at seven different pressures up to 8.779(11) GPa [a = 7.3170(4), c = 16.5955(5) Å and V = 769.46(9) Å 3 in R3m at 0.00010(1) GPa and a = 7.1594(8), c = 15.6003(17) Å and V = 692.49(8) Å 3 at 8.779(11) GPa]. The structural analysis shows that the 12-fold Na polyhedron accommodates most of the deformation by a large volume decrease (14%) and strong polyhedral distortion (63%). Our results indicate that natrojarosite has the most compressible structure of the supergroup studied sofar, and has a very strong axial anisotropy. [ABSTRACT FROM AUTHOR]

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 Dmeas = 2.25(2) g cm−3 and Dcalc = 2.338 g cm−3 for manganoblödite and Dmeas = 2.29(2) g cm−3 and Dcalc = 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: Na1.96(Mn0.44Mg0.29Co0.14Ni0.06)Σ0.93S2.03O8·4H2O. 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: Na1.96(Co0.36Mg0.30Mn0.17Ni0.12)Σ 0.95S2.02O8·4H2O. 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) Å3 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) Å3 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)(2̅01); 3.791(26)(2̅11); 3.338(21)(310); 3.291(100)(220, 021), 3.256(67)(211,1̅21), 2.968(22)(2̅21), 2.647(24)(4̅01); for cobaltoblödite: 4.551(80)(210, 011); 4.269(50)(2̅01); 3.795(18)(2̅11); 3.339(43)(310); 3.29(100)(220, 021), 3.258(58)(211, 1̅21), 2.644(21)( 4̅01), 2.296(22)( 1̅22). The crystal structures of both minerals were refined by single-crystal X-ray diffraction to R1 = 0.0459 (manganoblödite) and R1 = 0.0339 (cobaltoblödite). [ABSTRACT FROM AUTHOR]

The new mineral species oxycalcioroméite, Ca2Sb5+2 O6O, has been discovered at the Buca della Vena mine, Stazzema, Apuan Alps, Tuscany, Italy. It occurs as euhedral octahedra, up to 0.1 mm in size, embedded in dolostone lenses in the baryte + pyrite + iron oxides ore. Associated minerals are calcite, cinnabar, derbylite, dolomite, hematite, 'mica', pyrite, sphalerite and 'tourmaline'. Oxycalcioroméite is reddish-brown in colour and transparent. It is isotropic, with ncalc = 1.950. Electron microprobe analysis gave (wt.%; n = 6) Sb2O5 63.73, TiO2 3.53, SnO2 0.28, Sb2O3 10.93, V2O3 0.68, Al2O3 0.28, PbO 0.68, FeO 5.52, MnO 0.13, CaO 13.68, Na2O 0.83, F 1.20, O = F - 0.51, total 100.96. No H2O, above the detection limit, was indicated by either infrared or micro-Raman spectroscopies. The empirical formula, based on 2 cations at the B site, is (Ca1.073Fe2+0.338Sb3+0.330Na0.118 Pb0.013Mn0.008)Σ=1.880(Sb5+ 1.734Ti0.194V0.040Al0.024Sn0.008)Σ=2.000(O6.682F0.278)Σ6.960. The crystal structure study gives a cubic unit cell, space group Fd3m, with a 10.3042(7) Å, V 1094.06(13) Å 3, Z = 8. The five strongest X-ray powder diffraction lines are [d (Å)I (visually estimated)(hkl)]: 3.105(m)(311); 2.977(s)(222); 2.576(m)(400); 1.824(ms)(440); and 1.556(ms)(622). The crystal structure of oxycalcioroméite has been solved by X-ray single-crystal study on the basis of 114 observed reflections, with a final R1 = 0.0114. It agrees with the general features of the members of the pyrochlore supergroup. [ABSTRACT FROM AUTHOR]

Two Pbca orthopyroxene samples, donpeacorite (DP N.1) and enstatite (B22 N.60) with chemical formulae Mn0.54Ca0.03Mg1.43Si2O6 (XMn = 0.27) and Fe0.54Ca0.03Mg1.43Si2O6 (XFe = 0.27), respectively, were investigated by single-crystal X-ray diffraction at high-temperature conditions. The nearly identical XFe and XMn make the two samples the perfect candidates to investigate the effect of the compositional change at the M2 site (i.e. Fe-Mn substitution) on the thermal expansion behaviour of orthopyroxenes. Therefore, the unit-cell parameter thermal expansion behaviour of both samples has been investigated in the temperature range between room T and 1073 K. No evidence for phase transitions was found over that range. The two samples have been previously disordered with an ex situ annealing at ~1273 K. The unit-cell parameters and volume thermal expansion data, collected on the disordered samples, have been fitted to a Fei Equation of State (EoS) and the following coefficients obtained: V0 = 853.35(4) Å3, αV,303K = 2.31(24) × 10-5 K-1 and V0 = 845.40(6) Å3, aV,303K = 2.51(25) × 10-5 K-1 for DP N.1 and B22 N.60, respectively. While there is no difference in the volume thermal expansion coefficient as a function of composition and the expansion along the b direction is nearly identical for both samples, slight differences have been found along a and c lattice directions. The thermal expansion along the a direction is counterbalanced by that along c being responsible for the changes in lattice expansion scheme from αb > αc > αa at room T, to αc > αb > αa at high T. Therefore, as a result of the different behaviour along a and c, the unit-cell volume thermal expansion for both samples is identical within estimated standard deviations. The negligible effect of the Fe-Mn substitution on the bulk thermal expansion can be applied when dealing with geothermobarometry based on the elastic host-inclusion approach (e.g. Nestola et al., 2011; Howell et al., 2010; Angel et al., 2014a,b, 2015). In fact, though the compressibility effect is still not known, the nearly identical thermal expansion coefficients will not affect the entrapment pressure (Pe). [ABSTRACT FROM AUTHOR]

The high-pressure behaviour of the thaumasite structure was investigated using synchrotron powder X-ray diffraction, up to 19.5 GPa. Based on Rietveld refinements, thaumasite retained the roompressure P63 space group throughout the whole investigated pressure range while the pressure dependence of the refined unit-cell parameters can be cast into three different compression regimes, each corresponding to a different thaumasite phase (th-I, th-II and th-III) related by isosymmetric phase transitions. In particular, the phase transition in the 7.40-15.02 GPa P-range (i.e. from th-II to th-III) is associated with an inversion of the axial bulk moduli which, by analogy with ettringite, can be rationalized as due to a change in the relative strengths of the iono-covalent bonds along the [Ca3Si(OH)6(H2O)12]4+ columns parallel to the c axis vs. the O-H bonds linking the columns within the ab plane. The linear inverse relationship between the low- and high-temperature data from the literature with those collected under high-pressure conditions reveals that the same bonding regime governs the anisotropic expansion and contraction of thaumasite up to ~1.4 GPa and 400 K (HP-HT stability limits of th-I phase). [ABSTRACT FROM AUTHOR]