Ca Polyhedra Research Articles

Insight into carbonation reactivity of polycrystalline CS by DFT simulation

Monocalcium silicate (CS) is a promising carbon-sequestration cementitious material, but experimentally its polymorphs exhibit differing carbonation reactivity. This work utilized first-principles calculations to reveal the intrinsic mechanisms causing carbonation reactivity differences of α-CS, β-CS, and Para-CS by analyzing their crystal structure and electronic structure properties at the atomic scale. The results indicated that the order of carbonation reactivity is α-CS > Para-CS > β-CS. The carbonation of CS minerals depends on Ca-O bond breakage. Electrophilic attack associated with non-bridging oxygen atoms dominates the carbonation reaction. O-2p orbital and Ca-3d state are the main contributors to the electrophilic and nucleophilic reactivity. The crystal and electronic structure synergy enhances α-CS's carbonation reactivity. Analyzing the crystal and electronic structures showed α-CS has the lowest crystal cohesion and is structurally least stable due to its 3-member silica rings and co-edge linkage with Ca polyhedra. The larger volumes, lower bond order, and longer bond length of Ca-O polyhedra in α-CS cause weaker Ca-O bonds and more and easier Ca2+ dissolution than β- and Para- CS. The type and number of electrophilic active O sites in α-CS also facilitate Ca-O bond breaking and CO2 capture. These insightful revelations offer a systematic and efficient approach to identifying minerals demonstrating exceptional carbonation reactivity.

Paratobermorite, Ca4(Al0.5Si0.5)2Si4O16(OH)·2H2O·(Ca·3H2O), a new tobermorite-supergroup mineral with a novel topological type of the microporous crystal structure

Abstract A new mineral paratobermorite with the ideal crystal-chemical formula Ca4(Al0.5Si0.5)2Si4O16 (OH)·2H2O·(Ca·3H2O) is a member of the tobermorite group within the tobermorite supergroup. It was found at the Bazhenovskoe chrysotile asbestos deposit, Central Urals, Russia, in cavities of grossular rodingite in association with prehnite, pectolite, thomsonite-Ca, and calcite. Paratobermorite occurs as well-shaped prismatic to acicular crystals up to 1 × 1.5 × 8 mm3 typically assembled in spray- or bush-like radial clusters or open-work aggregates up to 1.5 cm across, which form interrupted crusts up to 3 × 5 cm2. Paratobermorite is transparent, colorless, pale yellowish, pale beige, or pinkish, with a vitreous luster. The mineral is brittle, with the (001) perfect cleavage. The Mohs hardness is ca. 3½. Dmeas = 2.51 (2) and Dcalc = 2.533 g/cm3. Paratobermorite is optically biaxial (+), α = 1.565 (2), β = 1.566 (2), γ = 1.578 (2), 2 Vmeas = 25 (10)° and 2 Vcalc = 32° (589 nm). Optical orientation is: X = c, Y = b, Z = a. The chemical composition of paratobermorite (electron microprobe, H2O by selective sorption from gaseous products of heating) is Na2O 0.40, K2O 0.28, CaO 36.60, MnO 0.04, BaO 0.07, Al2O3 6.46, SiO2 42.32, H2O 14.10, total 100.27 wt%. The empirical formula calculated on the basis of 22 O atoms per formula unit and (O,OH)17·5H2O is Na0.09K0.04Ca4.72Al0.92Si5.09O15.69(OH)1.31·5H2O. Like other members of the tobermorite supergroup, paratobermorite displays OD character, with two MDO (maximum degree of order) structures: one (MDO1), with non-standard space group F2/d11 and the second (MDO2), just corresponding to the structure-type of the new mineral, with non-standard space group C1121/m; its unit-cell parameters obtained from single-crystal X-ray diffraction data are: a = 11.2220(4), b = 7.3777(2), c = 22.9425(8) Å, γ = 89.990(3)°, V = 1899.46(10) Å3, and Z = 4; polytype 2M. The structure of paratobermorite is solved on a single crystal, R = 8.36%. Like structures of other “tobermorites 11 Å,” it is based on the complex layer built of a sheet of sevenfold Ca-centered polyhedra with wollastonite-type chains of T tetrahedra attached to the Ca-sheet from both sides. The tetrahedral (T) sites T1 and T2 are fully occupied by Si, while alternating T3 and T4 sites are filled by Al and Si in the ratio 1:1. The chains of tetrahedra belonging to neighboring complex layers share common oxygen vertices of the bridging T3,4 tetrahedra to form xonotlite-type ribbons [Si6O17]∞. The heteropolyhedral Ca-T-O scaffolding appears as a microporous quasi-framework with wide channels, which contain additional Ca atoms and H2O molecules. The complex Ca-T-O layers in paratobermorite (so-called “complex modules of type A”) significantly differ in topology (mutual arrangement of T tetrahedra and Ca polyhedra) from the complex Ca-T-O layers in tobermorite (“complex modules of type B”). IR spectrum confirms the presence of nonequivalent H2O molecules and nonequivalent T-O-T angles involving T atoms of two neighboring wollastonite-type chains. Due to the original topological type of the structure and the presence of significant amount of Al, which substitutes Si, paratobermorite can be considered as a novel microporous material, a perspective cation-exchanger.

The crystal structure of a new calcium aluminate phase containing formate

A new calcium aluminate phase containing formate ions was synthesized and its crystal structure determined. This new phase is indicated as M-phase and was firstly observed in Portland cement pastes hydrated in presence of Ca-formate and in excess of water. The crystal structure of the M-phase was successfully solved in the R-3 space group of the trigonal system on the basis of synchrotron X-ray single crystal diffraction data. The structural model was confirmed by Rietveld refinement of the powder diffraction data acquired on the synthesized pure sample. The crystal structure of the M-phase is similar to that of ettringite, being characterized by columns of AlO6 octahedra alternating with groups of three edge-sharing CaO7 polyhedra. The formate ions (HCOO)− share two oxygens with Ca polyhedra and are located in the interspace between the columns. The crystal structure of the M-phase testifies the strong interaction occurring between small organic molecules as formate and the calcium aluminate components of Portland cement.

Dioskouriite, CaCu4Cl6(OH)4∙4H2O: A New Mineral Description, Crystal Chemistry and Polytypism

A new mineral, dioskouriite, CaCu4Cl6(OH)4∙4H2O, represented by two polytypes, monoclinic (2M) and orthorhombic (2O), which occur together, was found in moderately hot zones of two active fumaroles, Glavnaya Tenoritovaya and Arsenatnaya, at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. Dioskouriite seems to be a product of the interactions involving high-temperature sublimate minerals, fumarolic gas and atmospheric water vapor at temperatures not higher than 150 °C. It is associated with avdoninite, belloite, chlorothionite, eriochalcite, sylvite, halite, carnallite, mitscherlichite, chrysothallite, sanguite, romanorlovite, feodosiyite, mellizinkalite, flinteite, kainite, gypsum, sellaite and earlier hematite, tenorite and chalcocyanite in Glavnaya Tenoritovaya and with avdoninite and earlier hematite, tenorite, fluorophlogopite, diopside, clinoenstatite, sanidine, halite, aphthitalite-group sulfates, anhydrite, pseudobrookite, powellite and baryte in Arsenatnaya. Dioskouriite forms tabular, lamellar or flattened prismatic, typically sword-like crystals up to 0.01 mm × 0.04 mm × 0.1 mm combined in groups or crusts up to 1 × 2 mm2 in area. The mineral is transparent, bright green with vitreous luster. It is brittle; cleavage is distinct. The Mohs hardness is ca. 3. Dmeas is 2.75(1) and Dcalc is 2.765 for dioskouriite-2O and 2.820 g cm−3 for dioskouriite-2M. Dioskouriite-2O is optically biaxial (+), α = 1.695(4), β = 1.715(8), γ = 1.750(6) and 2Vmeas. = 70(10)°. The Raman spectrum is reported. The chemical composition (wt%, electron microprobe data, H2O calculated by total difference; dioskouriite-2O/dioskouriite-2M) is: K2O 0.03/0.21; MgO 0.08/0.47; CaO 8.99/8.60; CuO 49.24/49.06; Cl 32.53/32.66; H2O(calc.) 16.48/16.38; -O=Cl −7.35/−7.38; total 100/100. The empirical formulae based on 14 O + Cl apfu are: dioskouriite-2O: Ca1.04(Cu4.02Mg0.01)Σ4.03[Cl5.96(OH)3.90O0.14]Σ10∙4H2O; dioskouriite-2M: (Ca1.00K0.03)Σ4.03(Cu4.01Mg0.08)Σ4.09[Cl5.99(OH)3.83O0.18]Σ10∙4H2O. Dioskouriite-2M has the space group P21/c, a = 7.2792(8), b = 10.3000(7), c = 20.758(2) Å, β = 100.238(11)°, V = 1531.6(2) Å3 and Z = 4; dioskouriite-2O: P212121, a = 7.3193(7), b = 10.3710(10), c = 20.560(3) Å, V = 1560.6(3) Å3 and Z = 4. The crystal structure (solved from single-crystal XRD data, R = 0.104 and 0.081 for dioskouriite-2M and -2O, respectively) is unique. The structures of both polytypes are based upon identical BAB layers parallel to (001) and composed from Cu2+-centered polyhedra. The core of each layer is formed by a sheet A of edge-sharing mixed-ligand octahedra centered by Cu(1), Cu(2), Cu(3), Cu(5) and Cu(6) atoms, whereas distorted Cu(4)(OH)2Cl3 tetragonal pyramids are attached to the A sheet on both sides, along with the Ca(OH)2(H2O)4Cl2 eight-cornered polyhedra, which provide the linkage of the two adjacent layers via long Ca−Cl bonds. The Cu(4) and Ca polyhedra form the B sheet. The difference between the 2M and 2O polytypes arises as a result of different stacking of layers along the c axis. The cation array of the layer corresponds to the capped kagomé lattice that is also observed in several other natural Cu hydroxychlorides: atacamite, clinoatacamite, bobkingite and avdoninite. The mineral is named after Dioskouri, the famous inseparable twin brothers of ancient Greek mythology, Castor and Polydeuces, the same in face but different in exercises and achievements; the name is given in allusion to the existence of two polytypes that are indistinguishable in appearance but different in symmetry, unit cell configuration and XRD pattern.

The high‐pressure phase of lawsonite: A single crystal study of a key mantle hydrous phase

AbstractLawsonite CaAl2Si2O7(OH)2·H2O is an important water carrier in subducting oceanic crusts and the primary hydrous phase in basalt at depths greater than ~80 km. We have conducted high‐pressure synchrotron single‐crystal X‐ray diffraction experiments on natural lawsonite at room temperature up to ~10.0 GPa to study its high‐pressure polymorphism. We find that lawsonite remains orthorhombic with Cmcm symmetry up to ~9.3 GPa and shows nearly isotropic compression. Above ~9.3 GPa, lawsonite becomes monoclinic with P21/m symmetry. Across the phase transition, the Ca polyhedron becomes markedly distorted, and the average positions of the H2O molecules and hydroxyls change. The changes observed in the H‐atom positions under compression are different than the low‐temperature changes in this material. We resolve for the first time the H‐bonding configuration of the high‐pressure monoclinic phase of lawsonite. A bond valence approach is deployed to determine that the phase transition from orthorhombic to monoclinic is primarily driven by the Si2O7 groups, and in particular their bridging oxygen atoms (O1). The changes in the structure strongly indicate that entropy increases across the symmetry‐lowering transition and hence that the slope of the phase transition is negative. Monoclinic lawsonite is thus stable under the pressure and temperature conditions that exist in the Earth and is likely to be a major water carrier in colder, deep subducted slabs. Monoclinic lawsonite also likely has enhanced electrical conductivity along its c axis due to its dynamically disordered hydrogen atoms.

HydropascoitE, Ca3(V10O28)·24H2O, A New Decavanadate Mineral From the Packrat Mine, Mesa County, Colorado

Abstract Hydropascoite, Ca 3 (V 10 O 28 )·24H 2 O, is a new mineral species (IMA2016-032) discovered in the Packrat mine, near Gateway, Mesa County, Colorado. It occurs as blades up to 2 mm in length on asphaltum associated with montroseite- and corvusite-bearing sandstone. Hydropascoite is dark yellow green, with a pistachio green streak, vitreous luster, Mohs hardness of ca . 1½, brittle tenacity, irregular fracture, and one perfect cleavage on {001}. Density (meas.) is 2.38(2) g/cm 3 . Hydropascoite is biaxial (–), with α 1.730(5), β 1.780(5), γ 1.790(5) (white light); 2 V (meas.) = 54.1(6)°, and extreme dispersion. The optical orientation is X ^ a ≈ 10°, Z ^ c* ≈ 20°. Hydropascoite is pleochroic, with X = bluish green, Y = orange, Z = yellowish green; X > Z > Y . Electron probe microanalysis gave the empirical formula (Ca 2.69 Na 0.30 ) Σ2.99 (H 0.31 V 5+ 10 O 28 )·24H 2 O, based on O = 52. Hydropascoite is triclinic, , a 10.08700(19), b 11.0708(2), c 21.8112(15) A, α 94.112(7)°, β 96.053(7)°, γ 116.398(8)°, V 2150.2(2) A 3 , and Z = 2. The strongest four lines in the diffraction pattern are [ d in A( I )( hkl )]: 8.92(100)(), 10.70(31)(002), 9.77(28)(010), and 7.4539(22)(). The atomic arrangement of hydropascoite was solved and refined to R 1 = 0.0488 for 8187 independent reflections with F > 4σ F . The structural unit in hydropascoite is the [V 10 O 28 ] 6– decavanadate group; charge balance in the structure is maintained by the [Ca 3 ·24H 2 O] 6+ interstitial complex. The three Ca polyhedra in the interstitial complex are not polymerized. Linkage between the structural unit and the components of the interstitial complex is principally by hydrogen bonding. In addition to the extensive hydrogen bonding, three oxygen atoms of the structural unit bond directly to calcium atoms of the interstitial complex. The mineral is named to recognize its chemical and structural similarity to pascoite, Ca 3 (V 10 O 28 )·17H 2 O, and its higher H 2 O content.

Hydroxylgugiaite: A New Beryllium Silicate Mineral From the Larvik Plutonic Complex, Southern Norway and the Ilímaussaq Alkaline Complex, South Greenland; The First Member of the Melilite Group To Incorporate A Hydrogen Atom

Abstract Hydroxylgugiaite, ideally (Ca 3 □ 1 ) Σ4 (Si 3.5 Be 2.5 ) Σ6 O 11 (OH) 3 , is a new mineral species from two localities in the Larvik plutonic complex in Porsgrunn, Telemark, Norway, and one locality in Ilimaussaq, Greenland. Hydroxylgugiaite crystals occur as squat dipyramids {111} (30 × 50 μm) or as elongate tetragonal prisms. The crystals are translucent, white to pale grey in color, with a white streak and vitreous luster. It is brittle, with no apparent cleavage. Hydroxylgugiaite is uniaxial positive with ω = 1.622 ± 0.002 and ϵ = 1.632 ± 0.002. There is no pleochroism and birefringence is low. The average of eight analyses of a single grain of type material (oxide wt.%) gave Na 2 O 2.04, CaO 32.90, FeO 0.22, MnO 0.74, BeO 13.47 (LA-ICP-MS), Al 2 O 3 0.74, SiO 2 44.06, F 1.74, H 2 O (assuming 3 OH + F) 4.93, Total (–0.73 O = F) 100.10. Potassium, strontium, and magnesium were measured but not detected. The calculated density is 2.79 g cm –3 . The empirical formula on the basis of 14 anions including 3 OH – + F – is: (Ca 2.76 Na 0.31 Mn 0.05 Fe 0.01 ) Σ3.13 (Si 3.45 Be 2.53 Al 0.07 ) Σ6.05 O 11 [(OH) 2.57 F 0.43 ] Σ3 . The formula from crystal-structure analysis of the Saga specimen is: (Ca 3.02 □ 0.98 ) Σ4 (Si 1.79 Be 0.21 ) Σ2 (Be 2.29 Si 1.71 ) Σ4 O 11 (OH) 3 . Combined structural and chemical data gives the following formula for the Nakkaalaaq specimen: (Ca 2.88 □ 0.98 Na 0.12 Mn 0.02 ) Σ4 (Si 1.80 Be 0.17 Al 0.03 ) Σ2 (Be 2.32 Si 1.68 ) Σ4 O 11 [(OH) 2.70 F 0.30 ] Σ3 ; with simplified formula (Ca,□) 4 (Si,Be) 2 (Be,Si) 4 O 11 (OH) 3 . The crystal structure of hydroxylgugiaite is tetragonal in acentric space group P 2 1 / m , with a 7.4151(2), b 7.4151, c 4.9652(1) A, V 272.9(1) A 3 , and Z = 1. It has been refined to an R index of 0.028 on the basis of 342 observed reflections and a correction for the {110} twin law. It is an H-bearing member of the melilite group. The structure has two distinct layers. The one crystallographically distinct Ca site with eight-fold coordination is a square antiprism polyhedron. The Ca polyhedra are in a layer with the H atoms. A second layer consists of corner-sharing Si/Be atoms in tetrahedral coordination with O. One H atom is bonded to an apical O atom that is not shared by two tetrahedra. This H atom is present only when there is a Ca -site vacancy. The other H atom is loosely bonded to the same O atom but at a different site. The IR spectrum supports this H-bonding scheme. Additional hydroxylgugiaite data is given for the other localities.

Mineralogy and Crystallography of Stokesite From Inner Mongolia, China

Abstract Stokesite, ideally CaSnSi 3 O 9 ·2H 2 O, is a rare hydrated calcium tin inosilicate mineral. The stokesite reported in this paper was found on the surface of large magnetite crystals within cavities of tin-iron ore at the Huanggangliang iron deposit, Chifeng, Inner Mongolia, China, and is associated with calcite, andradite, magnetite, vesuvianite, cassiterite, fluorite, quartz, mica, and clinochlore. Dominant forms are pinacoids {100} and {010} and orthorhombic bipyramid {344}. The empirical formula, calculated on the basis of nine O atoms per formula unit except for H 2 O, is (Ca 0.94 Mn 0.09 ) Σ1.03 (Sn 0.97 Fe 0.05 ) Σ1.02 Si 2.99 O 9 ·2H 2 O, Z = 4. The crystal structure of stokesite was refined in space group Pnna , a 14.4783(12), b 11.5879(10), c 5.2292(4) A, V 877.32(12) A 3 , R = 0.037. The crystal structure contains (Si 3 O 9 ) chains and Sn and Ca polyhedra. Here, we report and discuss the infrared spectrum, the differential thermal curve of stokesite, and the hydrogen bonding. Chifeng stokesite is a low-temperature hydrothermal mineral.

The crystal chemistry and the compressibility of silicate-carbonate minerals: Spurrite, galuskinite and tilleyite

Spurrite Ca5(SiO4)2(CO3), galuskinite Ca7(SiO4)3(CO3) and tilleyite Ca5(Si2O7)(CO3)2 are three representative minerals formed in high-temperature skarns in the silicate-carbonate system. Their crystal chemistry and compressibility have been investigated using first-principles theoretical simulation. These minerals are structurally described as the combination of interwoven layers constituted by Ca polyhedra and Si polyhedra, with the [CO3] triangles being “separators” to depolymerize the Si–Ca aggregations. With the effect of pressure, the Si polyhedra and the [CO3] groups present rigid behaviors whereas the Ca–O bonds undergo considerable compression. Several pressure-induced abnormities in the lattice parameter variations have been identified, revealing the existence of subtle changes in the compression process. Isothermal equations of state parameters are obtained: K0 = 71.1(1) GPa, V0 = 1003.31(4) Å3 and K0′ = 5.4(1) for spurrite; K0 = 75.0(1) GPa, V0 = 1360.30(7) Å3, K0′ = 5.4(1) for galuskinite, and K0 = 69.7(3) GPa, V0 = 1168.90(2) Å3 and K0′ = 4.0(1) for tilleyite. These compounds have similar K0 values to calcite CaCO3 but are much more compressible than larnite β-Ca2SiO4. Generally for these minerals, the bulk modulus exhibits a negative correlation with the [CO3] proportion. The structural and compressional properties of silicate-carbonate minerals compared with silicates and carbonates are expected to be a guide for further investigations on Si polyhedra and [CO3] coexistent phases.

An acentric calcium borate Ca2[B5O9]·(OH)·H2O: synthesis, structure, and nonliner optical property.

A novel noncentrosymmetric calcium borate, Ca2[B5O9]·(OH)·H2O (1), was synthesized under solvothermal condition using mixed solvents of pyridine and H2O. Compound 1 crystallizes in the monoclinic space group Cc. Its structure contains [B5O12] units and features a three-dimensional (3D) pcu net with nine-membered ring (9-MR) channels along the b-axis, where the Ca(2+) cations, OH(-) ions, and H2O molecules are located. Each Ca polyhedron shares three edges and one vertex with four neighbors to form a 3D dia Ca-O network. The pcu B-O net and dia Ca-O net are further interpenetrated to give the final denser net. The second harmonic generation (SHG) measurement shows that compound 1 is a type I phase-matchable material with a strong SHG response of ∼3 times that of KH2PO4. In addition, it exhibits a wide transparency range with a short UV cutoff edge below 200 nm. These results reveal that the compound is a potential deep-UV nonlinear optical material. The Vienna ab initio theoretical studies indicate the good SHG response is derived from the synergistic effect of the π-conjugated systems of BO3 groups and distorted CaO9 polyhedra.

Weddellite from renal stones: Structure refinement and dependence of crystal chemical features on H2O content

The refinement of the structures of 17 weddellite crystals [Ca(C 2 O 4 )·(2+ x )H 2 O, I 4/ m , a = 12.329–12.378 A, c = 7.345–7.366 A, V = 1117.8–1128.6 A 3 ], which were taken from the oxalic renal stones of the St. Petersburg (Russian Federation) citizens of both sexes aged from 24 to 65 years, has been carried out by the means of single-crystal X-ray diffraction ( R 1 = 0.024–0.057). According to the results of the study, the amount of “zeolitic” water molecules ( x ) in the structure of weddellite varies from 0.13 to 0.37 pfu. A significant positive correlation between the amount of “zeolitic” water in the structure of weddellite and the closest interatomic distance between coordination water molecules in the large channels (OW1-OW1) was found as well as positive correlation between the value of the a parameter and the average distance of in Ca polyhedron. Obtained linear regression equation: x = 5.43 a – 66.80, can be used for determination of the “zeolitic” water amount using the known unit-cell a parameter with mean-root-square error ±0.03 pfu. It was found that the x value for the crystals selected from the “mono-weddellite” stones ( x = 0.13–0.24) are at the bottom of the range, thus we can assume that weddellite crystals with fewer “zeolitic” water amounts would be relatively stable. This work expands the knowledge of pathogenic crystal growth processes in living organisms and the development of the theory of oxalate stone formation in humans and animals, and may provide a building block for biomolecular technologies that approach the prevention and treatment of diseases associated with lithiasis.

Structure and modeling of disorder in miserite from the Murun (Russia) and Dara-i-Pioz (Tajikistan) massifs

The structure, structural disorder and chemistry of miserite from the charoite-bearing rocks of the Murun massif (Russia) and from alkaline-syenite pegmatitic rocks of the Dara-i-Pioz massif (Tajikistan) were investigated employing a combination of electron microprobe, single crystal diffraction and micro-Fourier transform infrared spectroscopy analysis. Chemical analysis of the sample investigated by X-ray diffraction evidenced that Dara-i-Pioz miserite has a greater REE concentration than Murun miserite (~0.22 vs. 0.05 apfu, respectively) and also contains Y (0.14 apfu), which is absent in Murun miserite. The occurrence of a band at about 1,600 cm−1 testified to the presence of H2O in miserite at hand. Structural analyses yielded average cell parameters of a = 10.092, b = 16.016, c = 7.356 A, α = 96.60°, β = 111.27° and γ = 76.34°. Anisotropic structural refinement in space group P $$\bar{1}$$ converged at similar values for the analyzed samples (R ~3.4, R w ~3.8 %). An interesting feature shown by both the miserite specimen is the presence, revealed by difference Fourier analysis, of a disordered part of the structure. This turned out to be due to the flipping of the tetrahedra belonging to the isolated [Si2O7]6− diorthogroups, one of the two radicals (the other is [Si12O30]12−) characterizing the miserite structure. The sixfold and seven-vertex Ca polyhedra linked to the inverted diorthogroups show variation in coordination number with respect to those of the ordered structure.

Wopmayite, Ideally Ca6Na3 Mn(Po4)3(PO3Oh)4, A New Phosphate Mineral From The Tanco Mine, Bernic Lake, Manitoba: Description And Crystal Structure

Wopmayite, ideally Ca 6 Na 3 □Mn(PO 4 ) 3 (PO 3 OH) 4 , is a new secondary mineral from the Tanco mine, Bernic Lake, Manitoba. It occurs in vugs in a single 5–10 cm mass of phosphate-carbonate mineralization in a spodumene-rich boulder found in the dumps of the Tanco Mine, Bernic Lake, Manitoba, Canada. It is a secondary mineral that crystallized together with rhodochrosite, quartz, whitlockite, apatite, and other phases after dissolution of primary lithiophosphate by hydrothermal solutions. The initial crystal of wopmayite was a corroded {1011} rhomb ∼150 microns across. Wopmayite is colorless to white to pale pink with a white streak and a vitreous luster, and does not fluoresce under ultraviolet light. It has a Mohs hardness of 5, is brittle, has an irregular to subconchoidal fracture, and shows no cleavage or parting. The calculated density is 3.027 g/cm 3 . It is uniaxial (-), ω = 1.617, ɛ = 1.613, both ± 0.002. Wopmayite is hexagonal-rhombohedral, space group R 3 c , a 10.3926(2), c 37.1694(9) A, V 3476.7(2) A 3 , Z = 6, a:c = 1:3.577. The seven strongest lines in the X-ray powder-diffraction pattern are as follows: d (A), I , ( h k l ): 2.858, 100, (02.10); 3.186, 88, (234); 2.589, 68, (240); 5.166, 33, (120); 6.421, 32, (114); 8.017, 31, (012); and 3.425, 29, (1110). Chemical analysis by electron microprobe gave P 2 O 5 46.40, Al 2 O 3 0.38, Fe 2 O 3 0.80, FeO 0.96, MnO 3.74, MgO 0.41, CaO 37.65, SrO 0.91, Na 2 O 5.43, and H 2 O(calc) 2.00, sum 98.68 wt.%. The H 2 O content was determined by crystal-structure analysis. On the basis of 28 O apfu , the empirical formula is (Ca 7 .19 Na 1.88 Sr 0.09 ) Σ9.16 (Mn 0.56 Mg 0.11 Fe 2+ 0.14 Fe 3+ 0.11 Al 0.08 ) Σ1.00 (PO 4 ) 4.63 (PO 3 OH) 2.37 , and the endmember formula is Ca 6 Na 3 □Mn(PO 4 ) 3 (PO 3 OH) 4 . The crystal structure of wopmayite was solved by direct methods and refined to an R 1 index of 2.21% based on 2288 unique observed reflections collected on a three-circle rotating-anode ( M o K α X-radiation) diffractometer equipped with multilayer optics and an APEX-II detector. Wopmayite has a structural unit consisting of an [M 2+ (PO 4 ) 6 ] arrangement that is topologically the same as the structural units in the whitlockite and merrillite structures. The [M 2+ (PO 4 ) 6 ] clusters are linked by Ca polyhedra and (PO 3 Φ) groups of the form {Ca 9 X (PO 3 Φ)} where Φ = O,OH and X = (□, Na, Ca), depending on the mineral species. Wopmayite is related to whitlockite by the substitution Na + H → Ca + □, whereby Na is incorporated primarily at the Ca (3) site and H attaches to the P (1) tetrahedron to produce an acid-phosphate group. Thus merrillite contains no acid-phosphate group, whitlockite contains a single acid-phosphate group at P (3), and wopmayite contains acid-phosphate groups at both P (1) and P (3).

Volkovskite, a complex borate mineral: Refined crystallographic data and optics

Volkovskite [KCa 4 B 22 O 32 (OH) 10 Cl·4H 2 O] has been identified among numerous borate minerals obtained from potash deposits in New Brunswick. The crystals are vitreous, translucent, and colorless, varying from pale to deep orange. The crystals possess perfect {010} and {100} cleavages occurring as thinly layered pseudohexagonal/triangular, elongated platy masses. Volkovskite is biaxial positive, with indices of refraction α 1.539(2), β 1.540(2), and γ 1.605(2); 2 V Meas = 14.6°(7.2°), 2 V Calc . = 14.4°. There is no dispersion and no pleochroism. Volkovskite is triclinic, space group P 1 with cell parameters refined from the X-ray powder-diffraction pattern: a 6.539(3), b 24.194(5), c 6.576(3) A, α 92.2(4.4), β 119.1(1.3), γ 97.4(5.4)°, V 894.7(6) A 3 . The six strongest lines of the X-ray powder diffraction pattern [ d in A( I )( hkl )] are: 11.937(28.8)(020), 7.938(100)(030), 5.951(31.4)(040), 3.400(73.6)(070), 2.644(74.3)(090), and 1.983(13.0)(0120). A crystal structure refinement confirms the basic model of Rastsvetaeva et al. (1992). The crystal structure determination refined to R = 2.1% for 5266 unique reflections. The layered borate structure consists of a double layer of borate sheets parallel to (010). Between the double layers there are two types of cross linkage: Ca polyhedra bond two double layer slabs and K polyhedra bond the double slabs. Many borate minerals found in potash deposits form layered structures, such as biringuccite, nasinite, gowerite, veatchite polytypes, and volkovskite. The volkovskite structure obtained in this study is compared to related layered borates.

Calciodelrioite, Ca(VO3)2(H2O)4, the Ca analogue of delrioite, Sr(VO3)2(H2O)4

AbstractCalciodelrioite, ideally Ca(VO3)2(H2O)4, is a new mineral (IMA 2012-031) from the uraniumvanadium deposits of the eastern Colorado Plateau in the USA. The type locality is the West Sunday mine, Slick Rock district, San Miguel County, Colorado. The new mineral occurs on fracture surfaces in corvusite- and montroseite-impregnated sandstone and forms as a result of the oxidative alteration of these phases. At the West Sunday mine, calciodelrioite is associated with celestine, gypsum, huemulite, metarossite, pascoite and rossite. The mineral occurs as transparent colourless needles, bundles of tan to brown needles and star bursts of nearly black broad blades composed of tightly intergrown needles. Crystals are elongate and striated parallel to [100], exhibiting the prismatic forms {001} and {011} and having terminations possibly composed of the forms {100} and {61}. The mineral is transparent and has a white streak, subadamantine lustre, Mohs hardness of about 2½, brittle tenacity, irregular to splintery fracture, one perfect cleavage on {001} and possibly one or more additional cleavages parallel to [100]. Calciodelrioite is soluble in water. The calculated density is 2.451 g cm– 3. It is optically biaxial (+) with α = 1.733(3), β = 1.775(3), γ = 1.825(3) (white light), 2Vmeas = 87.3(9)° and 2Vcalc = 87°. The optical orientation is X = b; Z ≈ a. No pleochroism was observed. Electronmicroprobe analyses of two calciodelrioite samples and type delrioite provided the empirical formulae (Ca0.88Sr0.07Na0.04K0.01)Σ1.00(V1.00O3)2(H2.01O)4, (Ca0.76Sr0.21Na0.01)Σ0.98(V1.00O3)2(H2.01O)4 and (Sr0.67Ca0.32)Σ0.99(V1.00O3)2(H2.00O)4, respectively. Calciodelrioite is monoclinic, I2/a, with unit-cell parameters a = 14.6389(10), b = 6.9591(4), c = 17.052(2) Å, β = 102.568(9)°, V = 1695.5(3) Å3 and Z = 8. The seven strongest lines in the X-ray powder diffraction pattern [listed as dobs Å (I)(hkl)] are as follows: 6.450(100)(011); 4.350(16)(013); 3.489(18)(020); 3.215(17)(022); 3.027(50)(multiple); 2.560(28)(15,413); 1.786(18)(028). In the structure of calciodelrioite (refined to R1 = 3.14% for 1216 Fo > 4σF), V5+O5 polyhedra link by sharing edges to form a zigzag divanadate [VO3] chain along a, similar to that in the structure of rossite. The chains are linked via bonds to Ca atoms, which also bond to H2O groups, yielding CaO3(H2O)6 polyhedra. The Ca polyhedra form a chain along b. Each of the two symmetrically independent VO5 polyhedra has two short vanadyl bonds and three long equatorial bonds. Calciodelrioite and delrioite are isostructural and are the endmembers of the series Ca(VO3)2(H2O)4–Sr(VO3)2(H2O)4. Calciodelrioite is dimorphous with rossite, which has a similar structure; however, the smaller 8-coordinate Ca site in rossite does not accommodate Sr.

Acetate Bridged Trinuclear Zn, Ca and Mg Metal Complexes with 2- and 4-Substituted Pyridines

The structures of the complexes [Zn2(C5H6N2)2(C2H3O2)6Ca], compound 1; [Zn(C7H10N2)2Cl2] compound 2; and [Zn2(C5H6N2)2(C2H3O2)6Mg] compound 3 were established by spectral and X-ray diffraction studies. These complexes form part of the project of design and synthesis of new alkaline-earth metal complexes with multiple applications in the fields of catalysis, material science and biochemistry. Compound 1 crystallizes in the monoclinic space group P21/c with unit cell parameters a = 11.6918(11), b = 8.2850(8), c = 15.3472(15) A, β = 96.4140(10)°, Z = 2. Compound 2 crystallizes in the orthorhombic space group Pccn with unit cell parameters a = 13.6485(13), b = 14.2962(14), c = 18.2459(18) A, Z = 8. Compound 3 crystallizes in the monoclinic space group P21/c with unit cell parameters a = 7.5531(8), b = 22.905(3), c = 8.7137(9) A, Z = 2. All three structures (1–3) were solved by direct methods and refined to R = 0.0257, 0.0346 and 0.0244, respectively. For compound 1 crystallizes with the Ca2+ ion coincident with crystallographic centre of symmetry forming a dimer. The Ca2+ ion is six-fold coordinated by three acetate ligands. The Ca polyhedron may be described as a distorted tricapped trigonal prism. The Zn2+ ion is four-fold coordinated by three O atoms from three acetate groups (atoms O2, O4 and O5) and an N atom from the 2-aminopyridine moiety. The Zn polyhedral may be described as a distorted tetrahedral coordination. Compound 2 crystallizes as a crystallographic C2-symmetric complex, in which each Zn2+ ion is bound to two 4-dimethylaminopyridine units, and two Cl−1 ions. The tetracoordinated Zn atoms adopt a distorted tetrahedral geometry. Compound 3 crystallizes with the Mg2+ ion coincident with crystallographic centre of symmetry forming a dimer. The Mg2+ ion is octahedrally coordinated by six O atoms from three acetate groups. The Zn2+ ions are in a tetrahedral geometry. In the crystal structures 1 and 3, the molecules are stabilized by N–H······O; C–H······O interactions. However in the crystal structure 2, the molecules are stabilized by C–H·····Cl interactions. The crystal structures of three new acetate bridged trinuclear metal complexes with 2- and 4-substituted aminopyridines and their conformation were obtained by X-ray diffraction techniques from suitable single crystals. These complexes form part of the project for design and synthesis of new alkaline-earth metal complexes with multiple applications in the fields of catalysis, material science and biochemistry.

Crystallization, crystal-structure refinement, and IR spectroscopy of a synthetic hexahydroborite analog

The crystal structure of the hexahydroborite analog Ca[B(OH)4]2 · 2H2O (a = 7.9941(3) A, b = 6.6321(2) A, c = 7.9871(3) A, β = 104.166(4)°, V = 410.58(3) A3, sp. gr. P2/c, Z = 2, ρcalc = 1.891 g/cm3; Xcalibur S CCD automated diffractometer, 1196 reflections with I > 2σ(I), λMoKα), which was synthesized by the hydrothermal method via the recrystallization of calciborite CaB2O4 (M) in the M − B2O3 − H2O system (t = 250°C and P = 70–80 atm), was refined by the least-squares method with anisotropic displacement parameters (H atoms were located; R1 = 0.0260). The structure of synthetic hexahydroborite consists of infinite columns running along the c axis. The columns are formed by Ca polyhedra linked together and to [B(OH)4] orthotetrahedra by sharing edges. Along the two other axes, the translationally equivalent columns are linked only by hydrogen bonds. The presence of a stronger bond between the discrete (Ca-B-O) columns along the shortest (b = 6.6 A) axis accounts for the possibility of the shift of the columns by 1/2Tb and the formation of the second modification of Ca[B(OH)4]2 · 2H2O. The crystals of synthetic hexahydroborite were studied by IR spectroscopy. A crystal-chemical analysis was performed for a series of natural metaborates with the general formula CaB2O4 · nH2O (CaO: B2O3 = 1: 1, n = 0–6), including calciborite CaB2O4 and hexahydroborite CaB2O4 · 6H2O as the end members.

THE CRYSTAL STRUCTURE OF CAVANSITE: LOCATION OF THE H2O MOLECULES AND HYDROGEN ATOMS IN Ca(VO)(Si4O10)*4H2O

Cavansite, Ca(VO)(Si4O10)•4H2O, is a novel layer silicate, dimorphous with pentagonite. The earlier determination of its structure did not yield the location of the hydrogen atoms or clear resolution of the oxygen atoms of the H2O molecules. In this study, structures are reported from data collected at 100(2) and 296(2) K, and they clearly resolve and allow refinement of the position of the H atoms. The 100 K and 296 K structures were refined to R 1 values of 0.0141 and 0.0389, respectively. Cavansite is orthorhombic with space-group symmetry Pcmn , with a 9.7518(4), b 13.6854(6), and c 9.5965(4) A at 100 K, and a 9.7614(7), b 13.6666(10), and c 9.6049(7) A at 296 K. Cavansite consists of two layers, a layer of silicate tetrahedra and a layer formed of irregular CaO4(OH2)4 polyhedra and VO5 square-based pyramids that alternate in ribbons parallel to [100] in (010); the layers join laterally at the four corners of the base of the V pyramid. The silicate layer consists of four- and eight-membered rings of silicate tetrahedra with apices pointing along [010] or [010]. The four oxygen atoms in the Ca polyhedron that are not linked to the V square-based pyramids are part of H2O molecules. Adjacent ribbons in (010) are linked by hydrogen bonding.

THE CRYSTAL STRUCTURE OF VLADIMIRITE, WITH A REVISED CHEMICAL FORMULA, Ca4(AsO4)2(AsO3OH){middle dot}4H2O

Two samples of vladimirite, one from Bou Azzer, Morocco, and the other from a new occurrence in Copiapo, Chile (designated as R100075 and R080001, respectively), were examined with an electron microprobe, single-crystal X-ray diffraction, and Raman spectroscopy. Our results show that vladimirite is monoclinic with space group P 2 1 / c and unit-cell parameters a 5.8279(2), b 10.1802(4), c 22.8944(10) A, β 96.943(2)°, and V 1348.35(9) A 3 for R100075 and a 5.8220(1), b 10.1750(2), c 22.8816(6) A, β 96.902(1)°, and V 1345.66(5) A 3 for R080001. The structure determinations, with R 1 = 0.022 and 0.023 for R100075 and R080001, respectively, yielded an ideal chemical formula Ca 4 (AsO 4 ) 2 (AsO 3 OH)·4H 2 O (Z = 4) for this mineral, in contrast to Ca 5 (AsO 4 ) 2 (AsO 3 OH) 2 ·5H 2 O (Z = 3) documented in the literature. The chemical compositions for R100075 and R080001 are Ca 4.03 (AsO 4 ) 2 (As 0.99 O 3 OH)·4H 2 O and Ca 3.97 (AsO 4 ) 2 (As 1.01 O 3 OH)·4H 2 O, with trace Zn and Mn, respectively. The structure is characterized by undulating layers formed by the four nonequivalent, rather irregular Ca polyhedra [Ca1O 6 (H 2 O), Ca2O 6 (H 2 O), Ca3O 4 (H 2 O) 3 , and Ca4O 5 (H 2 O) 3 ] linked through the sharing of edges and vertices. These undulating layers are parallel to (010) and are interconnected by AsO 4 and AsO 3 OH tetrahedra, as well as hydrogen bonds, along the b axis. Vladimirite is remarkable inasmuch as one of the hydrogen-bonded O–H···O distances (O12H–H···O3) is only 2.465(2) A, which is the shortest donor–acceptor distance of all known Ca-bearing arsenate minerals, similar to the short donor–acceptor distances observed in several synthetic compounds containing AsO 3 OH groups.

Crystal structure of complex natural aluminum magnesium calcium iron oxide

The structure of a new natural oxide found near the Tashelga River (Eastern Siberia) was studied by X-ray diffraction. The pseudo-orthorhombic unit cell parameters are a = 5.6973(1) A, b = 17.1823(4) A, c = 23.5718(5) A, β = 90°, sp. gr. Pc. The structure was refined to R = 0.0516 based on 4773 reflections with |F| > 7σ(F) taking into account the twin plane perpendicular to the z axis (the twin components are 0.47 and 0.53). The crystal-chemical formula (Z = 4) is Ca2Mg2IVFe2(2+)IV[Al14VIO31(OH)][Al2IVO][AlIV]ALIV(OH)], where the Roman numerals designate the coordination of the atoms. The structure of the mineral is based on wide ribbons of edge-sharing Al octahedra (an integral part of the spinel layer). The ribbons run along the shortest x axis and are inclined to the y and z axes. The adjacent ribbons are shifted with respect to each other along the y axis, resulting in the formation of step-like layers in which the two-ribbon thickness alternates with the three-ribbon thickness. Additional Al octahedra and Mg and Fe2+ tetrahedra are located between the ribbons. The layers are linked together to form a three-dimensional framework by Al tetrahedra, Ca polyhedra, and hydrogen bonds with the participation of OH groups.