Alumovesuvianite,Ca19Al(Al,Mg)12Si18O69(OH)9, a new vesuvianite-group member from the Jeffrey mine,asbestos, Estrie region,Québec,Canada

Mineralogy and Petrology - Alumovesuvianite (IMA 2016–014), ideally Ca19Al(Al,Mg)12Si18O69(OH)9, is a new vesuvianite-group member found in the rodingite zone at the contact of a gabbroid...     

Refinement of the crystal structure of bonshtedtite, Na3Fe(PO4)(CO3)

The crystal structure of bonshtedtite, Na₃Fe(PO₄)(CO₃) (monoclinic, P2₁/m, a = 5.137(4), b = 6.644(4), c = 8.908(6) Å, β = 90.554(14)°, V = 304.0(4) ų, Z = 2) has been refined to R ₁ = 0.041 on the basis of 1314 unique reflections. The structure is similar to that of other minerals of the bradleyite group. It is based on the [Fe(PO₄)(CO₃)]^3? layers oriented parallel to (001). The layers are formed by corner-sharing PO₄ tetrahedra and FeO₄(CO₃) complexes, where FeO₆ tetrahedra and CO₃ triangles are edge-shared. The topology of the octa-tetrahedral layer in bonshtedtite is similar to that of the autunite-group minerals, but it differs from the latter in terms of local topological properties.     

Romanorlovite,a New Copper and Potassium Hydroxychloride from the Tolbachik Volcano,Kamchatka, Russia

A new mineral romanorlovite has been found in the upper, moderately hot zones of two fumaroles, Glavnaya Tenoritovaya (Major Tenorite) and Arsenatnaya (Arsenate), located at the second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. It is associated with avdoninite in both fumaroles, and in Glavnaya Tenoritovaya, it is also associated with belloite, sylvite, carnallite, mitscherlichite, sanguite, chlorothionite, eriochalcite, chrysothallite, and mellizinkalite. Romanorlovite occurs as prismatic, equant, or tabular tetragonal crystals up to 0.1 mm in size, crystal clusters up to 0.5 mm, and crusts up to 2 × 2 mm in area. The mineral is transparent with vitreous luster. Its color varies from yellow-brown to dark brown, and tiny crystals are honey- or golden-yellow. Cleavage is not observed. Romanorlovite is brittle. The Mohs hardness is ca ~3. The calculated density varies from 2.72 to 2.79 g/cm³ depending on the content of admixed Pb. The mineral is optically uniaxial (–), ω = 1.727(3), ε = 1.694(2). The Raman spectrum has been reported. The chemical composition of the holotype sample (wt %; electron microprobe data, contents of О and H calculated by stoichiometry) is as follows: 21.52 K, 0.89 Pb, 28.79 Cu, 0.02 Zn, 44.74 Cl, 4.85 O_calc, 0.41 H_calc, total 101.22. Its empirical formula calculated based on Cl₂₅ with (ОН)₄(Н2О)₂ is K_10.90Pb_0.09Cu_8.97Zn_0.01Cl₂₅(OH)₄ · 2H₂O. The simplified formula is K₁₁Cu₉Cl₂₅(OH)₄ · 2H₂O (Z = 4). Romanorlovite is tetragonal, space group[ I4/mmm. The unit cell parameters are (1) holotype: a = 17.5804(7), c = 15.9075(6) Å, V = 4916.5(3) ų; (2) the sample enriched in Pb on which the crystal structure was refined: a = 17.5538(19), c = 15.8620(17) Å, V= 4887.7(9) ų. The strongest reflections of the powder XRD pattern (d, Å–I[hkl]) are 12.48–56[110], 11.74–36[101], 8.80–100[200], 7.97–34[002], 6.71–40[112], 3.165–32[512], 2.933–80[215, 433], 2.607–38[514]. The mineral is named in honor of Roman Yu. Orlov (1929-2005), Russian mineralogist and physicist, who worked in the Department of Mineralogy, Moscow State University.     

Thermodynamics of arsenates,selenites, and sulfates in the oxidation zone of sulfide ores: I. Thermodynamic constants at ambient conditions

Understanding and deciphering processes proceeding near the surface are among the urgent tasks of contemporary mineralogy and geochemistry, which are especially important for resolving ecological challenges and developing principles of rational environmental management. The paper presents systematized data published on thermodynamics of minerals (arsenates, sulfates, selenites, and selenates), which are formed in the weathering zone of sulfide ores, and determines approaches to quantitative physicochemical modeling of their formation conditions. Diagrams of phase and chemical equilibria (Eh-pH, diagrams of solubility) of the subsystems of the model system Fe-Cu-Zn-Pb-Co-Ni-As-Se-S-H₂O (Fe²⁺, Fe³⁺, Cu²⁺, Zn²⁺, Pb²⁺, Ni²⁺, Co²⁺, H⁺//SeO₃²⁻, SeO₄²⁻, AsO₄³⁻, SO₄²⁻, OH⁻-H₂O) are used as a thermodynamic basis for modeling mineral-forming processes in the weathering zone of ore deposits. Seventy-two arsenates, about 70 sulfates, and 7 selenites and selenates have been identified in the framework of this system. The available published values of standard thermodynamic functions of the formation of minerals and chemical compounds are given, as well as the Pitzer equation parameters to describe the sulfate systems, which are substantially specific due to the high solubility of their components.     

Thermodynamics of Arsenates,Selenites, and Sulfates in the Oxidation Zone of Sulfide Ores. XIV. Selenium Minerals in the Oxidation Zone of the Yubileynoe Massive Sulfide Deposit,the South Urals

Selenium is one of the most important minor elements in massive sulfide ores. This study focuses on selenium minerals present in the oxidation zone of the Yubeleinoe massive sulfide deposit, the South Urals, Russia: clausthalite (PbSe), tiemannite (HgSe), and naumannite (Ag₂Se). These minerals are associated with goethite and siderite. Thermodynamic modeling was used to estimate the physicochemical parameters of selenide stability and the possible formation of Pb, Hg, and Ag selenites as a result of sulfide ore oxidation. The Eh–pH diagrams for the Fe–S–CO₂–H₂O and Fe–Se–CO₂–H₂O systems were calculated to estimate the physicochemical formation conditions of the Yubileinoe oxidation zone, as well as for the M–Se–Н₂О and M–S–H₂O (M = Hg, Pb, Ag) systems. The physicochemical parameters of clausthalite, naumannite, and tiemannite stability are consistent with these conditions. Only the formation of PbSeO3 is theoretically possible among Pb, Ag, and Hg selenites.

     

Refinement of the mangan-neptunite crystal structure

The crystal structure of mangan-neptunite, a manganese analogue of neptunite, has been refined in two space groups (Cc and C2/c). The mineral is monoclinic, with the correct space group Cc; the unit-cell dimensions are: a = 16.4821(6), b = 12.5195(4), c = 10.0292(3) Å, β = 115.474(1)°, and V = 1868.31 ų. The crystal structure has been refined to R ₁ = 0.0307 (wR ₂ = 0.0901) on the basis of 4892 observed reflections with |F _hkl | ≥ 4σ|F _hkl |. The most plausible acentric model is caused by the Ti- and (Fe, Mn, Mg)-ordering in the structure. Ti-octahedrons are strongly distorted and consist of short bond Ti-O (1.7 Å), one long bond (2.2 Å), and four equal bonds (2.0 Å). Fe-octahedrons are regularly shaped, with all Fe-O bonds being approximately identical.