Crystal chemistry of selenates with mineral-like structures: V. Crystal structures of (H3O)2[(UO2)(SeO4)2(H2O)](H2O)2 and (H3O)2[(UO2)(SeO4)2(H2O)](H2O), new compounds with rhomboclase and goldichite topology

The crystal structures of two new compounds (H₃O)₂[(UO₂)(SeO₄)₂(H₂O)](H₂O)₂ (1, orthorhombic, Pnma, a = 14.0328(18), b = 11.6412(13), c = 8.2146(13) Å, V = 134.9(3) ų) and (H₃O)₂[(UO₂)(SeO₄)₂(H₂O)](H₂O) (2, monoclinic, P2₁/c, a = 7.8670(12), b = 7.5357(7), c = 21.386(3) Å, β = 101.484(12)°, V = 1242.5(3) ų) have been solved by direct methods and refined to R ₁ = 0.076 and 0.080, respectively. The structures of both compounds contain sheet complexes [(UO₂)(SeO₄)₂]^2? formed by cornershared [(UO₂)O₄(H₂O)] bipyramids and SeO₄ tetrahedrons. The sheets are parallel to the (100) plane in structure 1 and to (?102) in structure 2. The [(UO₂)(SeO₄)₂(H₂O)]^2? layers are linked by hydrogen bonds via interlayer groups H₂O and H₃O⁺. The sheet topologies in structures 1 and 2 are different and correspond to the topologies of octahedral and tetrahedral complexes in rhomboclase (H₂O₂)⁺[Fe(SO₄)₂(H₂O)₂] and goldichite K[Fe(SO₄)₂(H₂O)₂](H₂O)₂, respectively.     

Epifanovite,NaCaCu5(PO4)4[AsO2(OH)2] · 7H2O: a New Mineral from the Kester Deposit,Sakha (Yakutia) Republic,Russia

Geology of Ore Deposits - Epifanovite, NaCaCu5(PO4)4[AsO2(OH)2] · 7H2O, a new natural copper, sodium and calcium arsenate–phosphate, has been found in a quartz–phosphate pocket...     

Kampelite,Ba3Mg1.5Sc4(PO4)6(OH)3·4H2O,a new very complex Ba-Sc phosphate mineral from the Kovdor phoscorite-carbonatite complex (Kola Peninsula,Russia)

Mineralogy and Petrology - Kampelite, Ba3Mg1.5Sc4(PO4)6(OH)3·4H2O, is a new Ba-Sc phosphate from the Kovdor phoscorite-carbonatite complex (Kola Peninsula, Russia). It is orthorhombic, Pnma,...     

Sergeysmirnovite,MgZn2(PO4)2 · 4H2O,a New Mineral from the Kester Deposit (Sakha-Yakutia,Russia)

Doklady Earth Sciences - Sergeysmirnovite, MgZn2(PO4)2 · 4H2O, is a new mineral from the oxidation zone of the Kester mineral deposit, Sakha-Yakutia, Russia. This mineral forms...     

Metastable Crystallization and Structural Complexity of Minerals

Doklady Earth Sciences - The physical basis has been elaborated for Goldsmith’s rule that states that the “ease” of crystallization of minerals is related to the simplicity (or...     

Thermodynamics of arsenates,selenites, and sulfates in the oxidation zone of sulfide ores. X. thermal stability and dehydration features of synthetic analogs of the cobaltomenite–ahlfeldite solid solution series

The aim of this study is the experimental investigation of the synthetic analogs of cobaltomenite, CoSeO₃ ? 2H₂O, ahlfeldite, NiSeO₃ ? 2H₂O, members of the cobaltomenite–ahlfeldite solid solution series (Ni _x Co_1–x )SeO₃ ? 2H₂O, and singularities of their dehydration and dissociation. The intermediate members of the cobaltomenite (CoSeO₃ ? 2H₂O)–ahlfeldite (NiSeO₃ ? 2H₂O) series have been synthesized and studied with a combination of X-ray diffraction, scanning electron microscopy, and the simultaneous application of thermogravimetry (TG) and differential scanning calorimetry (DSC) within the temperature range from 25 to 640°C. The complete solid solution series corresponds to the monoclinic space group P2₁/n. Unit-cell dimensions decrease in all crystallographic directions as the amount of Ni increases. The angle β increases from 98.82(1) (cobaltomenite) to 99.05(1)° (ahlfeldite). It has been established that CoSeO₃ ? 2H₂O and NiSeO₃ ? 2H₂O dehydrate at 120–340°C through two stages apparently corresponding, to the formation of intermediate hydrated species CoSeO₃ ? H₂O and NiSeO₃ ? 1/3H₂O. The reaction enthalpies for each dehydration stage of CoSeO₃ ? 2H₂O and NiSeO₃ ? 2H₂O have been determined. Changes of the unit-cell dimensions and dehydration temperatures are rationalized in terms of the Co and Ni site occupancy in the structure of the cobaltomenite–ahlfeldite solid-solution series members.     

The thermodynamics of arsenates,selenites, and sulfates in the oxidation zone of sulfide ores. XI. Solubility of synthetic chalcomenite analog and zinc selenite at 25°C

The aim of this study is the synthesis of CuSeO₃·2H₂O (chalcomenite analog), ZnSeO₃·2H₂O, and ZnSeO₃·H₂O and the investigation of their solubility in water. CuSeO₃·2H₂O has been synthesized from solutions of Cu nitrate and Na selenite, while Zn selenites were synthesized from solutions of Zn nitrate and Na selenite. The samples obtained have been examined with X-ray diffraction and infrared and Raman spectroscopy. The solubility has been determined using the isothermal saturation method in ampoules at 25°C. The solubility has been calculated using the Geochemist’s Workbench (GMB 9.0) software package. Solubility products have been calculated for CuSeO₃·2H₂O (10^–10.63), ZnSeO₃·2H₂O (10^–8.35), and ZnSeO₃·H₂O (10^–7.96). The database used comprises thermodynamic characteristics of 46 elements, 47 base particles, 48 redox pairs, 551 particles in solution, and 624 solid phases. The Eh–pH diagrams of the Zn–Se–H₂O and Cu–Se–H₂O systems were plotted for the average contents of these elements in underground water in oxidation zones of sulfide deposits.     

Mineral systems and the thermodynamics of selenites and selenates in the oxidation zone of sulfide ores – a review

Mineralogy and Petrology - Contemporary mineralogy and geochemistry are concerned with understanding and deciphering processes that occur near the surface of the Earth. These processes are...     

Batisite,Na2BaTi2(Si4O12)O2, from Inagli massif,Aldan, Russia: crystal-structure refinement and high-temperature X-ray diffraction study

Mineralogy and Petrology - The crystal structure of batisite, Na2BaTi2 (Si4O12)O2, from the Inagli massif (Aldan, Yakutia, Russia) was refined to R 1 = 0.032 for 1449 unique...