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1.
The new mineral sardignaite, a bismuth molybdate with formula BiMo2O7(OH)·2H2O, occurs in quartz veins within a granitic rock at Su Senargiu, near Sarroch, Sardegna, Italy. The name is after the locality. Sardignaite occurs a thin prismatic crystals up to 1 mm in length, with pale yellow color and a white streak. It is transparent with adamantine lustre, non fluorescent, and brittle with a conchoidal fracture. It is associated with bismuthinite, bismoclite, molybdenite, ferrimolybdite, koechlinite, wulfenite, and the new mineral IMA 2009–022. Mohs hardness is ca. 3. D calc is 4.82 g/cm3. The mineral is monoclinic, space group P21/m, with a 5.7797(7), b 11.567(1), c 6.3344(8) Å, β 113.360(9)°, V 388.8(1) Å3. The strongest lines in the powder X-ray diffraction pattern are d(I)(hkl): 3.206(100)(031), 5.03(80)(?101), 1.992(45)(221), 3.120(32)(130). The crystal structure of sardignaite was solved to R(F) 0.056 using single-crystal X-ray diffraction data, and is characterized by edge-sharing dimers of [MoO5(H2O)] octahedra, linked to each other through corner-sharing to give rise to corrugated columns running along b. Such columns are held together by Bi3+ cations, eight-fold coordinated by 7 O + 1 (OH). Both the mineral and its name were approved by the IMA-CNMNC.  相似文献   

2.
A new mineral, mariinskite, BeCr2O4, the chromium analog of chrysoberyl, has been found at the Mariinsky (Malyshevo) deposit, the Ural Emerald Mines, the Central Urals, Russia. The mineral is named after its type locality. It was discovered in chromitite in association with fluorphlogopite, Cr-bearing muscovite, eskolaite, and tourmaline. Mariinskite occurs as anhedral grains ranging from 0.01 to 0.3 mm in size; in some cases it forms pseudohexagonal chrysoberyl-type twins. The mineral is dark-green, with a pale green streak; the Mohs’ hardness is 8.5, microhardness VHN = 1725 kg/mm2. D meas = 4.25(2) g/cm3, D calc = 4.25 g/cm3. Microscopically, it is emerald-green, pleochroic from emerald-green (γ) to yellow-green (β) and greenish yellow (α). The new mineral is biaxial (+), γ = 2.15(1), β = 2.09(3), and α = 2.05(1), 2V meas = 80 ± (10)°, 2V calc = 80.5°. In reflected light, it is gray with green reflections; R max (589) = 12.9%; R min (589) = 12.3%, and there are strong, internal green reflections. The strongest absorption bands in the IR spectrum are as follows (cm?1): 935, 700, 614, 534. Space group Pnma, a = 9.727(3), b = 5.619(1), c = 4.499(1) Å, V = 245.9(3) Å3, Z = 4. The strongest reflections in the X-ray powder diffraction pattern are as follows (d Å, I, hkl): 4.08(40)(101), 3.31(90)(111), 2.629(50)(301), 2.434(50)(220), 2.381(40)(311), 2.139(60)(221), 1.651(100)(222). The average chemical composition of mariinskite (electron microprobe, wt %) is as follows: BeO 16.3, Al2O3 23.89, Cr2O3 58.67, Fe2O3 0.26, V2O3 0.26, TiO2 0.61, total is 99.98. The empirical formula, calculated on the basis of four O atoms is Be1.03(Cr1.22Al0.74Ti0.01Fe0.01V0.01)1.99O4. The compatibility index 1 ? (Kp/Kc), 0.019, is excellent. The type specimens are deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow, and the Ural Geological Museum, Yekaterinburg, Russia.  相似文献   

3.
The crystal structure of a knorringite-type compound, Mg3(Cr1.58Mg0.21Si0.21)Si3O12, synthesized in a multi-anvil press at P = 16 GPa and T = 1,600 °C, was refined from single-crystal X-ray diffraction data up to R = 2.36 % for 314 independent reflections. Garnet was found to be cubic and have space group Ia $\overline{3}$ d, with the unit cell parameters a = 11.5718 (1) Å, V = 1,549.54 (2) Å3. The knorringite crystal studied contains 21 mol% of majorite end-member. The structural characterization of knorringitic garnet is important because the study of its thermodynamic constants provides new constraints on thermobarometry of peridotitic garnet assemblages of the lowermost upper mantle. The Raman spectra of synthetic knorringite have been obtained for the first time.  相似文献   

4.
Abramovite, a new mineral species, has been found as fumarole crust on the Kudryavy volcano, Iturup Island, Kuriles, Russia. The mineral is associated with pyrrhotite, pyrite, würtzite, galena, halite, sylvite, and anhydrite. Abramovite occurs as tiny elongated lamellar crystals up to 1 mm long and 0.2 mm wide (average 300 × 50 μ m), which make up chaotic intergrowths in the narrow zone of fumarole crust formed at ～600°C. Most crystals are slightly striated along the elongation. The new mineral is silver gray, with a metallic luster and black streak. Under reflected light, abramovite is white with a yellowish gray hue. It has weak bireflectance; anisotropy is distinct without color effects. The chemical composition (electron microprobe) is as follows, wt %: 20.66 S, 0.98 Se, 0.01 Cu, 0.03 Cd, 11.40 In, 12.11 Sn, 37.11 Pb, 17.30 Bi; the total is 99.60. The empirical formula calculated on the basis of 12 atoms is Pb1.92Sn1.09In1.06Bi0.89(S6.90Se0.13)7.03. The simplified formula is Pb2SnInBiS7. The strongest eight lines in the X-ray powder pattern [d, Å (I)(hkl)] are 5.90(36)(100), 3.90(100)(111), 3.84(71)(112), 3.166(26)(114), 2.921(33)(115), 2.902(16)(200), 2.329(15)(214), 2.186(18)(125). The selected area electron diffraction (SAED) patterns of abramovite are quite similar to those of the homologous cylindrite series minerals. The new mineral is characterized by noncommensurate structure composed of regularly alternated pseudotetragonal and pseudohexagonal sheets. The structure parameters determined from the SAED patterns and X-ray powder diffraction data for pseudotetragonal subcell are: a = 23.4(3), b = 5.77(2), c = 5.83(1) Å, α = 89.1(5) °, β = 89.9(7)°, γ = 91.5(7)°, V = 790(8) Å3; for pseudohexagonal subcell: a = 23.6(3), b = 3.6(1), c = 6.2(1) Å, α = 91(2)°, β = 92(1)°, γ = 90(2)°, V = 532(10) Å3. Abramovite is triclinic, space group P(1). The new mineral is named in honor of Russian mineralogist Dmitry Abramov. The type material of abramovite has been deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow.  相似文献   

5.
The thermo-elastic behaviour of Be2BO3(OH)0.96F0.04 (i.e. natural hambergite, Z = 8, a = 9.7564(1), b = 12.1980(2), c = 4.4300(1) Å, V = 527.21(1) Å3, space group Pbca) has been investigated up to 7 GPa (at 298 K) and up to 1,100 K (at 0.0001 GPa) by means of in situ single-crystal X-ray diffraction and synchrotron powder diffraction, respectively. No phase transition or anomalous elastic behaviour has been observed within the pressure range investigated. P?V data fitted to a third-order Birch–Murnaghan equation of state give: V 0 = 528.89(4) Å3, K T0 = 67.0(4) GPa and K′ = 5.4(1). The evolution of the lattice parameters with pressure is significantly anisotropic, being: K T0(a):K T0(b):K T0(c) = 1:1.13:3.67. The high-temperature experiment shows evidence of structure breakdown at T > 973 K, with a significant increase in the full-width-at-half-maximum of all the Bragg peaks and an anomalous increase in the background of the diffraction pattern. The diffraction pattern was indexable up to 1,098 K. No new crystalline phase was observed up to 1,270 K. The diffraction data collected at room-T after the high-temperature experiment showed that the crystallinity was irreversibly compromised. The evolution of axial and volume thermal expansion coefficient, α, with T was described by the polynomial function: α(T) = α 0 + α 1 T ?1/2. The refined parameters for Be2BO3(OH)0.96F0.04 are: α 0 = 7.1(1) × 10?5 K?1 and α 1 = ?8.9(2) × 10?4 K ?1/2 for the unit-cell volume, α 0(a) = 1.52(9) × 10?5 K?1 and α 1(a) = ?1.4(2) × 10?4 K ?1/2 for the a-axis, α 0(b) = 4.4(1) × 10?5 K?1 and α 1(b) = ?5.9(3) × 10?4 K ?1/2 for the b-axis, α 0(c) = 1.07(8) × 10?5 K?1 and α 1(c) = ?1.5(2) × 10?4 K ?1/2 for the c-axis. The thermo-elastic anisotropy can be described, at a first approximation, by α 0(a):α 0(b):α 0(c) = 1.42:4.11:1. The main deformation mechanisms in response to the applied temperature, based on Rietveld structure refinement, are discussed.  相似文献   

6.
Single crystals of B2O3 are needed for the precise determination of the refractive indices used to calculate the electronic polarizability α of 3-coordinated boron. The α(B) values in turn are used to predict mean refractive indices of borate minerals. Since the contribution of boron to the total polarizability of a mineral is very low, the synthetic compound B2O3 represents an ideal model system because of its high molar content of boron. Millimeter-sized crystals were synthesized at 1 GPa in a piston-cylinder apparatus. The samples were heated above the liquidus (800 °C), subsequently cooled at 15 °C/h to 500 °C and finally quenched. The refractive indices were determined by the immersion method using a microrefractometer spindle stage. The refractive indices n o = 1.653 (3) and n e = 1.632 (3) correspond to a total polarizability for B2O3 of α = 4.877 Å3. These values were used to determine the electronic polarizability of boron of α(B) = 0.16 Å3. Although the surface of the B2O3 crystals was coated with a hydrous film immediately after being exposed to air, its bulk crystallinity is retained for a period of at least 2 months.  相似文献   

7.
It was not possible to carry out a complete analyses of crystal, as the experiment by Ding and Shi et al.. It's analysis precision R=0.25 or more big than this, which value are not satisfied for single crystal study, but we through many test and found the best: [R(int)=14.5%]. The final fullmatix least-squares refinement on F2 converged to R1=0.0791 and wR2=0.1864 for 704 observed reflections [I 3 2s(I)]. Daomanite is orthorhombic system, space group Cmc21, a=3.7520(8))?, b=15.844(4) ?, c=5.8516(12) ?, α=β=γ=90°. V=347.86(14)?3, Z=4. Daomanite chemical formula is Cu Pt AsS 2. Idealized composition Me+M2+M2+S2=CuS ·PtA s S. There is no other similar mineral in the world.  相似文献   

8.
Lisiguangite, CuPtBiS3, is a new mineral species discovered in a PEG-bearing, Co-Cu sulfide vein in garnet pyroxenite of the Yanshan Mountains, Chengde Prefecture, Hebei Province, China. It is associated with chalcopyrite and bornite, galena, minor pyrite, carrolite, molybdenite and the platinum-group minerals daomanite (CuPtAsS2), Co-bearing malanite (Cu(Pt, Co)2S4) sperrylite, moncheite, cooperite and malyshevite (CuPdBiS3), rare damiaoite (Pt2In3) and yixunite (Pt3In). Lisiguangite occurs as idiomorphic crystals, tabular or lamellae (010) and elongated [100] or as aggregates, up to 2 mm long and 0.5 mm wide. The mineral is opaque, has lead-gray color, black streak and metallic luster. The mineral is non-fluorescent. The observed morphology displays the following forms: pinacoids {100}, {010}, {001}, and prism {110}. No twining is observed. The a:b:c ratio, calculated from unit-cell parameters, is 0.6010:1:0.3836. Cleavage: {010} perfect, {001} distinct, {100} may be visible. H Mohs: 21/2; VHN25=46.7-49.8 (mean 48.3) kg/mm2. Tenacity: brittle. Lisiguangite is bright white with a yellowish tint. In reflected light it shows neither internal reflections nor bireflectance or pleochroism. It has weak to moderate anisotropy (blue-greenish to brownish) and parallel-axial extinction. The reflectance values in air (and in oil) for R3, R4 and (imR3, imR4), at the standard Commission on Ore Mineralogy wavelengths are: 37.5, 35.7 (23.4, 22.3) at 470 nm; 38.6, 36.5 (23.6, 22.6) at 546 nm; 39.4, 37.5 (23.6, 22.7) at 589 nm and 40.3, 38.2 (23.7, 22.9) at 650 nm. The average of eight electron-microprobe analyses: Cu 12.98, Pt 30.04, Pd 2.69, Bi 37.65 and S 17.55, totaling 100.91%, corresponding to Cu1.10(Pt 0.83, Pd0.14)Σ0.97Bi0.97S2.96 based on six atoms apfu. The ideal formula is CuPtBiS3. The mineral is orthorhombic. Space group: P212121, a=7.7152(15)?,b=12.838(3)?, c=4.9248(10)?, V=487.80(17)?3, Z=4. The six strongest lines in the X-ray powder-diffraction pattern [d in ? (I) (h k l) are 6.40(30)(020), 3.24(80)(031), 3.03(100)(201), 2.27(40)(051), 2.14(50)(250), 1.865(60)(232).  相似文献   

9.
The crystal chemistry of paratacamite has been re-evaluated by studying a crystal from the holotype specimen BM86958 of composition Cu3.71Zn0.29(OH)6Cl2 using single-crystal X-ray diffraction at 100, 200, 300, 353, 393 and 423 K. At 300 K paratacamite has space group $R\bar{3}$ with unit-cell parameters a 13.644 and c 14.035 Å and exhibits a pronounced subcell, a′ = ½a and c′ = c, analogous to that of the closely related mineral herbertsmithite, Cu3Zn(OH)6Cl2. Between 353 and 393 K, paratacamite undergoes a reversible phase transformation to the herbertsmithite-like substructure, space group $R\bar{3}m$ , unit-cell parameters a 6.839 and c 14.072 Å (393 K). The transformation is characterised by a gradual reduction in intensity of superlattice reflections, which are absent at 393 and 443 K. On cooling from 443 to 300 K at ~10 K min?1, the superlattice reflections reappear and the refined structures ( $R\bar{3}$ ) of the initial and recovered 300 K states are almost identical. The complete reversibility of the transformation establishes that paratacamite of composition Cu3.71Zn0.29(OH)6Cl2 is thermodynamically stable at ambient temperatures. The nature of the rhombic distortion of the M(2)O6 octahedron is discussed by considering two possibilities that are dependent upon the nature of cation substitution in the interlayer sites.  相似文献   

10.
Hydroxylborite, a new mineral species, an analogue of fluoborite with OH > F, has been found at the Titovsky deposit (57°41′N, 125°22′E), the Chersky Range, Dogdo Basin, Sakha-Yakutia Republic, Russia. Prismatic crystals of the new mineral are dominated by the {10\(\overline 1 \)0} faces without distinct end forms and reach (1?1.5) × (0.1?0.2) mm in size. Radial aggregates of such crystals occur in the mineralized marble adjacent to the boron ore (suanite-kotoite-ludwigite). Calcite, dolomite, Mg-rich ludwigite, kotoite, szaibelyite, clinohumite, magnetite, serpentine, and chlorite are associated minerals. Hydroxylborite is transparent colorless, with a white streak and vitreous luster. The new mineral is brittle. The Mohs’ hardness is 3.5. The cleavage is imperfect on {0001}. The density measured with equilibration in heavy liquids is 2.89(1) g/cm3; the calculated density is 2.872 g/cm3. The wave numbers of the absorption bands in the IR spectrum of hydroxylborite are (cm?1; sh is shoulder): 3668, 1233, 824, 742, 630sh, 555sh, 450sh, and 407. The new mineral is optically uniaxial, negative, ω = 1.566(1), and ε = 1.531(1). The chemical composition (electron microprobe, H2O measured with the Penfield method, wt %) is 18.43 B2O3, 65.71 MgO, 10.23 F, 9.73 H2O, 4.31-O = F2, where the total is 99.79. The empirical formula calculated on the basis of 6 anions pfu is as follows: Mg3.03B0.98[(OH)2.00F1.00]O3.00. Hydroxylborite is hexagonal, and the space group is P63/m. The unit-cell dimensions are: a = 8.912(8) Å, c = 3.112(4) Å, V = 214.05(26) Å3, and Z = 2. The strongest reflections in the X-ray powder pattern [d, Å (I, %)(hkil)] are: 7.69(52)(01\(\overline 1 \)0), 4.45(82)(11\(\overline 2 \)0), 2.573(65)(03\(\overline 3 \)0), 2.422(100)(02\(\overline 2 \)1), and 2.128(60)(12\(\overline 3 \)1). The compatibility index 1 ? (K p/K c) is 0.038 (excellent) for the calculated density and 0.044 (good) for the measured density. The type material of hydroxylborite is deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow (inventory number 91968) and the Geological Museum of the All-Russia Institute of Mineral Resources, Moscow (inventory number M-1663).  相似文献   

11.
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12.
A new mineral species, named naquite(FeSi), is found in the podiform chromitites of the Luobusha ophiolite in Qusong County, Tibet, China. The detailed composition is Fe 65.65, Si 32.57 and Al 1.78 wt%. The mineral is cubic, space group P213. The irregular crystals range from 15 to 50 μm in diameter and form an intergrowth with luobusaite. Naquite is steel grey in color, opaque, with a metallic lustre and gives a grayish-black streak. The mineral is brittle, has a conchoidal fracture and no apparent cleavage. The estimated Mohs hardness is 6.5, and the calculated density is 6.128 g/cm3. Unit-cell parameters are a 4.486 (4) ?, V 90.28 (6) ?3, Z=4. The five strongest powder diffraction lines [d in ? (hkl) (I/I0)] are: 3.1742 (110) (40), 2.5917(111) (43), 2.0076 (210) (100), 1.8307 (211) (65), and 1.1990 (321) (36). Originally called ‘fersilicite’, the species and new name have now been approved by the CNMNC (IMA 2010–010).  相似文献   

13.
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14.
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 Ocalc, 0.41 Hcalc, total 101.22. Its empirical formula calculated based on Cl25 with (ОН)4(Н2О)2 is K10.90Pb0.09Cu8.97Zn0.01Cl25(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) Å3; (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) Å3. 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.  相似文献   

15.
《地学前缘(英文版)》2020,11(6):2339-2346
A new cerite group mineral species, taipingite-(Ce), ideally (Ce73+, Ca2)Σ9Mg(SiO4)3[SiO3(OH)]4F3, has been found in the Taipingzhen rare earth element (REE) deposit in the North Qinling Orogen (NQO), Central China. It forms subhedral grains (up to approximately 100 ​μm ​× ​200 ​μm) commonly intergrown with the REE mineral assemblages and is closely associated with allanite-(Ce), gatelite-(Ce), törnebohmite-(Ce), fluocerite-(Ce), fluocerite-(La), fluorite, bastnäsite-(Ce), parisite-(Ce) and calcite. Taipingite-(Ce) is light red to pinkish brown under a binocular microscope and pale brown to colorless in thin section, and it is translucent to transparent with a grayish-white streak and vitreous luster. This mineral is brittle with conchoidal fracture; has a Mohs hardness value of approximately 5½ and exhibits no cleavage twinning or parting. The calculated density is 4.900(5) g/cm3. Optically, taipingite-(Ce) is uniaxial (+), with ω ​= ​1.808(5), ε ​= ​1.812(7), c ​= ​ε, and a ​= ​b ​= ​ω. Furthermore, this mineral is insoluble in HCl, HNO3 and H2SO4. Electron microprobe analysis demonstrated that the sample was relatively pure, yielding the empirical formula (with calculated H2O): (Ce4.02La1.64Nd1.49Pr0.41Sm0.10Gd0.02Ho0.02Tm0.01Lu0.02Y0.03Ca0.66Mg0.05Th0.01–0.51)Σ9(Mg0.75Fe0.253+)Σ1(SiO4)3{[SiO3(OH)]3.98[PO3(OH)]0.02}Σ4(F1.81OH1.17Cl0.02)Σ3. Taipingite-(Ce) is trigonal and exhibits space group symmetry R3c with unit cell parameters a ​= ​10.7246(3) Å, c ​= ​37.9528(14) Å, V ​= ​3780.39(20) Å3 and Z ​= ​6. The strongest eight lines in the X-ray diffraction pattern are [d in Å(I)(hkl)]: 4.518(50)(202), 3.455(95)(122), 3.297(85)(214), 3.098(35)(300), 2.941(100)(02,10), 2.683(65)(220), 1.945(40)(238) and 1.754(40)(30,18). The crystal structure has been refined to a R1 factor of 0.025, calculated for the 2312 unique observed reflections (Fo ​≥ ​4σ). The mineral is named after its discovery locality and is characterized as the F-dominant analogue of cerite-(Ce).  相似文献   

16.
A single crystal of natrolite, Na2Al2Si3O10 ·2H2O (space group Fdd2), was studied by X-ray diffraction methods at room temperature. The intensities were measured in a complete sphere of reflection up to sinΘ/ λ=0.903 Å?1. A refinement of high-order diffraction data yielded residuals of R/(F)=0.9%, Rw(F)=0.8%, GoF=1.40 for 1856 high-angle reflections (0.7≤sinΘ/ λ≤0.903 Å?1) and R(F)=1.0%, Rw(F)=1.2%, GoF=3.07 for all 3471 independent reflections in the complete sphere of reflection. The X-X method was used to calculate deformation electron densities (DED) in natrolite. Within all tetrahedra, residual electron density-was found in the T-O bond directions indicating a considerable covalent contribution to the chemical bond. The range of the interatomic peak heights was from 0.19 to 0.34 e/Å3 in the SiO4 tetrahedra and from 0.11 to 0.23 e/Å3 in the AlO4 tetrahedron. The ionic contribution to the chemical bond manifests itself in the displacement of the peaks towards the oxygen atoms. Charge displacement due to interaction of nonframework cations with framework oxygen atoms as well as electron densities attributable to the lone pair orbitals in the water molecule have been observed.  相似文献   

17.
Single crystals of the garnet Mn2+ 3Mn3+ 2[SiO4]3 and coesite were synthesised from MnO2-SiO2 oxide mixtures at 1000°C and 9 GPa in a multianvil press. The crystal structure of the garnet [space group Ia3¯d, a=11.801(2) Å] was refined at room temperature and 100 K from single-crystal X-ray data to R1=2.36% and R1=2.71%, respectively. In contrast to tetragonal Ca3Mn3+ 2[GeO4]3 (space group I41/a), the high-pressure garnet is cubic and does not display an ordered Jahn-Teller distortion of octahedral Mn3+. A disordered Jahn-Teller distortion either dynamic or static is evidenced by unusual high anisotropic displacement parameters. The room temperature structure is characterised by following bond lengths: Si-O=1.636(4) Å (tetrahedron), Mn3+-O=1.995 (4) Å (octahedron), Mn2+-O=2.280(5) and 2.409(4) Å (dodecahedron). The cubic structure was preserved upon cooling to 100 K [a=11.788(2) Å] and upon compressing up to 11.8 GPa in a diamond-anvil cell. Pressure variation of the unit cell parameter expressed by a third-order Birch-Murnaghan equation of state led to a bulk modulus K 0=151.6(8) GPa and its pressure derivatives K′=6.38(19). The peak positions of the Raman spectrum recorded for Mn2+ 3Mn3+ 2[SiO4]3 were assigned based on a calderite Mn2+ 3Fe3+ 2[SiO4]3 model extrapolated from andradite and grossular literature data.  相似文献   

18.
A new mineral kobyashevite, Cu5(SO4)2(OH)6·4H2O (IMA 2011–066), was found at the Kapital’naya mine, Vishnevye Mountains, South Urals, Russia. It is a supergene mineral that occurs in cavities of a calcite-quartz vein with pyrite and chalcopyrite. Kobyashevite forms elongated crystals up to 0.2 mm typically curved or split and combined into thin crusts up to 1?×?2 mm. Kobyashevite is bluish-green to turquoise-coloured. Lustre is vitreous. Mohs hardness is 2½. Cleavage is {010} distinct. D(calc.) is 3.16 g/cm3. Kobyashevite is optically biaxial (?), α 1.602(4), β 1.666(5), γ 1.679(5), 2 V(meas.) 50(10)°. The chemical composition (wt%, electron-microprobe data) is: CuO 57.72, ZnO 0.09, FeO 0.28, SO3 23.52, H2O(calc.) 18.39, total 100.00. The empirical formula, calculated based on 18 O, is: Cu4.96Fe0.03Zn0.01S2.01O8.04(OH)5.96·4H2O. Kobyashevite is triclinic, $ P\overline{\,1 } $ , a 6.0731(6), b 11.0597(13), c 5.5094(6)?Å, α 102.883(9)°, β 92.348(8)°, γ 92.597(9)°, V 359.87(7)?Å3, Z?=?1. Strong reflections of the X-ray powder pattern [d,Å-I(hkl)] are: 10.84–100(010); 5.399–40(020); 5.178–12(110); 3.590–16(030); 2.691–16(20–1, 040, 002), 2.653–12(04–1, 02–2), 2.583–12(2–11, 201, 2–1–1), 2.425–12(03–2, 211, 131). The crystal structure (single-crystal X-ray data, R?=?0.0399) сontains [Cu4(SO4)2(OH)6] corrugated layers linked via isolated [CuO2(H2O)4] octahedra; the structural formula is CuCu4(SO4)2(OH)6·4H2O. Kobyashevite is a devilline-group member. It is named in memory of the Russian mineralogist Yuriy Stepanovich Kobyashev (1935–2009), a specialist on mineralogy of the Urals.  相似文献   

19.
A pyroxene with composition LiNiSi2O6 was synthesized at T = 1,473 K and P = 2.0 GPa; the cell parameters at T = 298 K are a = 9.4169(6) Å, b = 8.4465(7) Å, c = 5.2464(3) Å, β = 110.534(6)°, V = 390.78(3) Å3. TEM examination of the LiNiSi2O6 pyroxene showed the presence of h + k odd reflections indicative of a primitive lattice, and of antiphase domains obtained by dark field imaging of the h + k odd reflections. A HT in situ investigation was performed by examining TEM selected area diffraction patterns collected at high temperature and synchrotron radiation powder diffraction. In HTTEM the LiNiSi2O6 was examined together with LiCrSi2O6 pyroxene. In LiCrSi2O6 the h + k odd critical reflections disappear at about 340 K; they are sharp up to the transition temperature and do not change their shape until they disappear. In LiNiSi2O6 the h + k odd reflections are present up to sample deterioration at 650 K. A high temperature synchrotron radiation powder diffraction investigation was performed on LiNiSi2O6 between 298 and 773 K. The analysis of critical reflections and of changes in cell parameters shows that the space group is P-centred up to the highest temperature. The comparative analysis of the thermal and spontaneous strain contributions in P21/c and C2/c pyroxenes indicates that the high temperature strain in P-LiNiSi2O6 is very similar to that due to thermal strain only in C2/c spodumene and that a spontaneous strain contribution related to pre-transition features is not apparent in LiNiSi2O6. A different high-temperature behaviour in LiNiSi2O6 with respect to other pyroxenes is suggested, possibly in relation with the presence of Jahn–Teller distortion of the M1 polyhedron centred by low-spin Ni3+.  相似文献   

20.
Two samples of hydroxyl-clinohumite, sample SZ0407B with approximate composition Mg8.674(14)Fe0.374(4)(Si0.99(1)O4)4(OH)2 and sample SZ0411B with composition Mg9(SiO4)4(OH)2, were synthesized at 12 GPa and 1,250 °C coexisting with olivine. Unit-cell parameters determined by single-crystal X-ray diffraction are given as follows: a = 4.7525(4) Å, b = 10.2935(12) Å, c = 13.7077(10) Å, α = 100.645(9)°, V = 659.04(9) Å3 for SZ0407B, and a = 4.7518(6) Å, b = 10.2861(12) Å, c = 13.7008(9) Å, α = 100.638(9)°, V = 658.15(9) Å3 for SZ0411B. Single-crystal X-ray intensity data were collected for crystal structure refinements of both samples. Relative to the pure-Mg sample, Fe decreases M3–OH bond lengths by ~0.010(3) Å, consistent with some ferric iron ordering into M3. Raman spectroscopy shows two strong bands in the lattice-mode region at 650 and 690 cm?1 in the Fe-bearing sample, which are not observed in the pure-Mg sample. Spectra in the H2O region show at least five bands, which are deconvolved into seven distinct O–H-stretching modes. Thermal expansion measurements were carried out for both samples from 153 to 787 K by single-crystal X-ray diffraction. The average a-, b-, c-axial and volumetric thermal expansion coefficients (10?6 K?1) are 10.5(1), 12.3(2), 12.5(2) and 34.9(5) for SZ0407B, respectively, and 11.1(1), 12.6(3), 13.7(3), 36.8(6) for SZ0411B, respectively. After heating, the unit-cell parameters were refined again for each sample at ambient condition, and no significant changes were observed, indicating no significant oxidation or dehydration during the experiment. For the DHMS phases along the brucite–forsterite join, linear regression gives a systematic linear decrease in expansivity with increasing density. Further, substitution of ferrous iron into these structures decreases thermal expansivity, making the Fe-bearing varieties slightly stiffer.  相似文献   

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