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The re-investigation of [Bi2O2(OH)](NO3), dioxidodibismuth(III) hydroxide nitrate, on the basis of single-crystal X-ray diffraction data revealed an apparent structural phase transition of a crystal structure determined previously (space group Cmc21 at 173 K) to a crystal structure with lower symmetry (space group Pna21 at 100 K). The Cmc21 → Pna21 group–subgroup relationship between the two crystal structures is klassengleiche with index 2. In contrast to the crystal structure in Cmc21 with orientational disorder of the nitrate anion, disorder does not occur in the Pna21 structure. Apart from the disorder of the nitrate anion, the general structural set-up in the two crystal structures is very similar: [Bi2O2]2+ layers extend parallel to (001) and alternate with layers of (OH)− anions above and (NO3)− anions below the cationic layer. Whereas the (OH)− anion shows strong bonds to the BiIII cations, the (NO3)− anion weakly binds to the BiIII cations of the cationic layer. A rather weak O—HO hydrogen-bonding inter­action between the (OH)− anion and the (NO3)− anion links adjacent sheets along [001]. [ABSTRACT FROM AUTHOR]

Apexite (IMA2015-002), NaMg(PO4)⋅9H2O, is a new mineral from the Apex mine, Lander County, Nevada, U.S.A., where it occurs as a low-temperature secondary mineral on massive quartz matrix in association with andersonite, calcite, čejkaite, gaylussite, and goethite. Apexite forms colorless needles up to 0.5 µm in length. The streak is white. Crystals are transparent and have vitreous to satiny luster. The Mohs hardness is about 2, the tenacity is brittle, the fracture is curved, and crystals exhibit one perfect cleavage on {100}. The measured density is 1.74(1) g/cm³ and the calculated density is 1.741 g/cm³. Electron microprobe analyses provided: Na2O 9.26, MgO 14.42, P2O5 23.31, H2O 53.01 (structure), total 100.00 wt% (normalized). The empirical formula (based on 13 O apfu) is: Na0.91Mg1.09P1.00O13.00H17.91. Apexite is triclinic, P..., a = 6.9296(7), b = 11.9767(13), c = 14.9436(19) Å, α = 92.109(6), β = 102.884(7), γ = 105.171(7)°, V = 1160.9(2) ų, and Z = 4. The eight strongest lines in the X-ray powder diffraction pattern are [dobs in Å(I)(hkl)]: 14.63(35)(001); 5.11(61)(021,...1,110,...20); 4.68(75)(0...2,...2,1...1,0...3); 4.301(96)(102,013,022,...13); 4.008(44) (...3,1...2); 2.876(46)(040); 2.762(100)(...3,2...1,0...4,...04,015); and 2.507(30)(212,025,...3). Apexite is a new struvite-type phase with a unique structure (R1 = 4.44% for 1401 Fo > 4σF) consisting of four components: (1) a [Na2Mg4(H2O)14]10+ heteropolyhedral cation cluster; (2) a trans edge-sharing chain of Na(H2O)6 octahedra; (3) an isolated PO4 group; and (4) an isolated H2O group. The structural components are linked to one another only via hydrogen bonds. Its structure is related to that of hazenite. [ABSTRACT FROM AUTHOR]

A sample of Sb-rich segnitite from the Black Pine mine, Montana, U.S.A., has been studied by microprobe analyses, single-crystal X-ray diffraction, and μ-EXAFS and XANES spectroscopy. Linear combination fitting of the spectroscopic data provided Sb5+:Sb3+ = 85(2):15(2), where Sb5+ is in octahedral coordination substituting for Fe3+ and Sb3+ is in tetrahedral coordination substituting for As5+. Based upon this Sb5+:Sb3+ ratio, the microprobe analyses yielded the empirical formula Pb1.02 H1.02(Fe3+2.36Sb5+0.41Cu2+0.27)Σ3.04(As5+1.78Sb3+0.07S6+0.02)Σ1.88O8(OH)6.00. The crystal structure refinement and bond valence analysis are consistent with these cation site assignments. The formation of Sb-rich segnitite opens new possibilities for Sb sinks within the supergene zone. Segnitite may, in fact, be an ideal host for the sequestering of several toxic elements for pH < 2. At higher pH values, As is more likely to be incorporated into schwertmannite and ferrihydrite. [ABSTRACT FROM AUTHOR]

Single-crystal diffraction of jarosite, KFe33+(SO4)2(OH)6, has been undertaken at low temperatures that proxy for martian surface conditions. Room-temperature data are consistent with literature data [a = 7.2913(5), c = 17.1744(17), and V = 790.72(11) in R...m], while the first low-temperature data for the mineral is presented (at 253, 213, 173, and 133 K). Data collections between 297 and 133 K show strongly anisotropic thermal expansion, with the c axis much more expandable than the a axis. Much of the anisotropy is due to strong distortion of the KO12 polyhedron, which increases by 8% between 297 and 133 K. The data sets can aid in the identification of jarosite by X-ray diffraction of martian soils using the Curiosity Rover's CheMin instrument. [ABSTRACT FROM AUTHOR]

The Distortion Theorem implies that the irregularity of bond distances in a distorted coordination polyhedron causes an increase of mean bond distance. Examination of 40 polyhedra containing the lone-pair cation TeIV shows that this does not imply an increase in polyhedral volume. Volumes of these polyhedra are 10.3-23.7 Å3, compared with the 12.83 Å3 expected for a hypothetical regular octahedron. There is little correlation between volume and measures of polyhedral distortion such as quadratic elongation, bond-angle variance or vector bond valence. However, the oxygens of our polyhedra lie very close to a sphere of best fit, centred at ∼ 1 Å from the TeIV atom. The TeIV-centre distance is an index of lone-pair stereoactivity and is linearly related to the radius Rsph of the sphere; this is explained by a more localized lone pair repelling the anions more strongly, leading to a longer non-bonded distance between the lone pair and anions. Polyhedral volume still varies considerably for a given Rsph, because the oxygen ligands may be distributed over the whole sphere surface, or confined to a small portion of it. The uniformity of this distribution can be estimated from the distance between the sphere centre and the centroid of the O6 polyhedron. TeIV-centre and centroid-centre distances alone then account for 95% of the variation observed in volume for polyhedra which are topologically octahedral. Six of the polyhedra studied that are outliers are closer in shape to pentagonal pyramids than octahedra. These have short distances from the central TeIV cation to other TeIV and/or to large, polarizable cations, suggesting additional weak bonding interactions between these species and the central lone pair. The flexibility of lone-pair polyhedra is further enhanced by the ability of a single polyhedron to accommodate different cations with different degrees of lone-pair activity, which facilitates more diverse solid solution behaviour than would otherwise be the case. [ABSTRACT FROM AUTHOR]

Pericytes are cells that reside on the wall of the blood vessels and their primary function is to maintain the vessel integrity. Recently, it has been realized that pericytes have a much greater role than just the maintenance of vessel integrity essential for the development and formation of a vascular network. Pericytes also have stem cell-like properties and are seemingly able to differentiate into adipocytes, chondrocytes, osteoblasts and granulocytes, leading them to be identified as mesenchymal stem cells (MSCs). More recently it has been suggested that pericytes play a key role in wound healing, whereas the beneficial effects of MSCs in accelerating the wound healing response has been recognized for some time. In this review, we collate the most recent data on pericytes, particularly their role in vessel formation and how they can affect the wound healing process. [ABSTRACT FROM AUTHOR]

Eckhardite, (Ca, Pb)Cu2+Te6+O5(H2O), is a new tellurate mineral from Otto Mountain near Baker, California, U.S.A. It occurs in vugs in quartz in association with Br-rich chlorargyrite, gold, housleyite, khinite, markcooperite, and ottoite. It is interpreted as having formed from the partial oxidation of primary sulfides and tellurides during or following brecciation of quartz veins. Eckhardite is mono-clinic, space group P21/n, with unit-cell dimensions a = 8.1606(8), b = 5.3076(6), c = 11.4412(15) Å, β = 101.549(7)°, V= 485.52(10) ų, and Z = 4. It forms as needles or blades up to about 150 x 15 x 5 µm in size, typically in radial or sub-radial aggregates, but also as isolated needles. The color is light bluish green and the streak is very pale bluish green. Crystals are transparent with vitreous to subadamantine luster. The Mohs hardness is estimated at between 2 and 3. Eckhardite is brittle with an irregular fracture and one likely (but not observed) cleavage on {101}. The calculated density based on the empirical formula is 4.644 g/cm³. The mineral is biaxial (-), with indices of refraction of a = 1. 770 (calc), β = 1.860 (calc), and β = 1.895(5). The measured 2V is 61.2(5)°, dispersion is r < v, perceptible and the optical orientation is Z = b; X ≈ [101]. The pleochroism is: Z (light blue green) < Y (very pale blue green) 4sF) consists of stair-step-like octahedral layers of Te6+O6 and Cu2+O6 octahedra parallel to {101}, which are linked in the [101] direction by bonds to interlayer Ca atoms. The structure can be described as a stacking of stepped HCP layers alternating with chains of CaO7 polyhedra. The structures of bairdite, timroseite, and paratimroseite also contain stair-step-like HCP polyhedral layers. [ABSTRACT FROM AUTHOR]

Bairdite, Pb2Cu42+Te26+O10(OH)2(SO4)(H2O), is a new tellurate-sulfate from Otto Mountain near Baker, California, U.S.A. It occurs in vugs in quartz associated with khinite, cerussite, goethite, and hematite. It is interpreted as having formed from the partial oxidation of primary sulfides and tellurides during or following brecciation of quartz veins. Bairdite is monoclinic, space group P21/c, with unit-cell dimensions a = 14.3126(10), b = 5.2267(3), c = 9.4878(5) Å, b = 106.815(7)°, V = 679.41(7) Å3, and Z = 2. Bairdite occurs as diamond-shaped tabular crystals up to about 250 mm long and 5 mm thick, in subparallel and fan-shaped aggregates. The color is lime green, the streak is pale lime green, and the luster is adamantine. The Mohs hardness is estimated at between 2 and 3. Bairdite is brittle with an irregular fracture and one perfect cleavage on {100}. The calculated density based on the empirical formula is 6.062 g/cm3. Bairdite is biaxial (+), with calculated indices of refraction of a = 1.953, b = 1.966, and g = 2.039. The measured 2V is 47(2)°, dispersion is r < v, strong and the optical orientation is Y = b; Z ^ a = 34° in obtuse angle b. The pleochroism is strong: Z (pale green) <<< X (green) < Y (green). Electron microprobe analyses (average of 4) provided: PbO 34.22, CaO 0.06, CuO 23.80, TeO3 26.34, SO3 5.74, H2O 2.81 (structure), total 92.97 wt%. The empirical formula (based on 17 O atoms pfu) is: Pb2.05Ca0.01Cu2+3.99Te6+2.00S0.96O17.00H4.16. The eight strongest powder X-ray diffraction lines are [dobs in Å (hkl) I]: 4.77 (110,102) 50, 4.522 (002,011,111) 66, 3.48 (multiple) 62, 2.999 (311,411) 97, 2.701 (502,113,213) 79, 2.614 (013,020) 100, 1.727 (multiple) 65, and 1.509 (911,033,324) 83. The crystal structure of bairdite (R1 = 0.072 for 1406 reflections with Fo > 4σF) contains edge-sharing chains of Te6+O6 and Cu2+O6 octahedra parallel to b that are joined by corner-sharing in the a direction, forming thick stair-step-like hexagonal close packed layers parallel to {100}. The polyhedral sheet has similarities to those in the structures of timroseite and paratimroseite. The thick interlayer region contains PbO10 polyhedra and half-occupied SO4 groups. Raman and infrared spectral data are presented [ABSTRACT FROM AUTHOR]

Bond-valence parameters r0 and b have been re-determined for TeIV-O: r0 = 1.9605 Å, b = 0.41; TeVI-O: r0 = 1.921 Å, b = 0.56; and TeIV-Cl: r0 = 2.3115 Å, b = 0.555. Bond distance data from 208 independent TeIV-O polyhedra, 118 TeVI-O polyhedra and 26 TeIV-Cl polyhedra were used, and all neighbours out to 3.5 Å were included. Root-mean square deviations of bond-valence sums on Te from ideal values were 0.1934, 0.1939 and 0.0865 v.u. The good fit for TeIV-O over a range of Te coordination numbers from 3 to 12 demonstrates that there is no essential difference in character between short `primary' Te-O bonds, oriented away from the Te lone pair, and longer `secondary' Te-O bonds on the same side of the Te atom as the lone pair. Comparison of bond-valence sums for Te-O polyhedra obtained using the new parameters with those calculated using earlier literature values shows that the new parameters give a narrower spread of calculated bond-valence sums, which means much closer to the formal valence for both oxidation states of tellurium. [ABSTRACT FROM AUTHOR]

The garnet supergroup includes all minerals isostructural with garnet regardless of what elements occupy the four atomic sites, i.e., the supergroup includes several chemical classes. There are presently 32 approved species, with an additional 5 possible species needing further study to be approved. The general formula for the garnet supergroup minerals is {X3}[Y2](Z3)φ12, where X, Y, and Z refer to dodecahedral, octahedral, and tetrahedral sites, respectively, and φ is O, OH, or F. Most garnets are cubic, space group ... (no. 230), but two OH-bearing species (henritermierite and holtstamite) have tetragonal symmetry, space group, I41/acd (no. 142), and their X, Z, and φ sites are split into more symmetrically unique atomic positions. Total charge at the Z site and symmetry are criteria for distinguishing groups, whereas the dominant-constituent and dominant-valency rules are critical in identifying species. Twenty-nine species belong to one of five groups: the tetragonal henritermierite group and the isometric bitikleite, schorlomite, garnet, and berzeliite groups with a total charge at Z of 8 (silicate), 9 (oxide), 10 (silicate), 12 (silicate), and 15 (vanadate, arsenate), respectively. Three species are single representatives of potential groups in which Z is vacant or occupied by monovalent (halide, hydroxide) or divalent cations (oxide). We recommend that suffixes (other than Levinson modifiers) not be used in naming minerals in the garnet supergroup. Existing names with suffixes have been replaced with new root names where necessary: bitikleite-(SnAl) to bitikleite, bitikleite-(SnFe) to dzhuluite, bitikleite-(ZrFe) to usturite, and elbrusite-(Zr) to elbrusite. The name hibschite has been discredited in favor of grossular as Si is the dominant cation at the Z site. Twenty-one end-members have been reported as subordinate components in minerals of the garnet supergroup of which six have been reported in amounts up to 20 mol% or more, and, thus, there is potential for more species to be discovered in the garnet supergroup. The nomenclature outlined in this report has been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (Voting Proposal 11-D). [ABSTRACT FROM AUTHOR]

Areas of non-coding DNA, originally termed "junk DNA", contain sequences for small non-coding RNAs, which when processed into smaller products called microRNAs (miRNAs), facilitate a high level of control on gene transcription and protein production. MiRNAs have been identified in the skin controlling processes such as cell proliferation, differentiation and apoptosis, and as such they have been shown to have important roles in skin morphogenesis, wound healing and regeneration. They can exert control by up-regulating as well as down-regulating specific processes. Additionally, there is a high degree of complexity with miRNAs with one miRNA capable of controlling many genes and more than one miRNA per gene so they can potentially offer a broad treatment therapy rather than a single gene targeting approach. Thus, miRNAs provide an interesting and exciting opportunity to develop new therapeutics and for furthering our understanding of the regulatory control in disease. Here we review the current knowledge of miRNA expression and function in the skin and how miRNAs may modulate wound repair and tissue regeneration. [ABSTRACT FROM AUTHOR]

Fuettererite, Pb3Cu 62+Te6+O6(OH)7Cl5, is a new tellurate from Otto Mountain near Baker, California, named for Otto Fuetterer who is largely responsible for the development of the mining claims on Otto Mountain. The new mineral is known from only two specimens, one from the NE2 vein and the other from the Bird Nest drift. Fuettererite occurs in vugs in quartz, on the first specimen associated with Br-rich chlorargyrite, iodargyrite, and telluroperite and on the second specimen associated with anglesite, anatacamite, atacamite, chalcopyrite, galena, goethite, hematite, muscovite, phosphohedyphane, timroseite, and wulfenite. It is interpreted as having formed from the partial oxidation of primary sulfides and tellurides during or following brecciation of quartz veins. Fuettererite is hexagonal, with space group R3, α = 8.4035(12), c = 44.681(4) Å, V = 2732.6(6) Å3, and Z = 6. Crystals are tabular to short prismatic, exhibit the forms {100}, {101}, and {001} and reach a maximum dimension of 50 µm. The color is bluish green, the streak is pale bluish-green, and the luster is adamantine. The Mohs hardness is estimated at between 2 and 3. The new mineral is brittle with irregular fracture and one perfect cleavage on {001}. The calculated density based on the empirical formula is 5.528 g/cm³. Fuettererite is uniaxial (-), with calculated indices of refraction of ω = 2.04 and ε = 1.97, and is dichroic bluish-green, E < O. Electron microprobe analysis provided: PbO 41.45, CuO 30.35, Al2O3 0.23, TeO3 12.80, Cl 12.08, H2O 3.55 (structure), O=Cl -2.73, total 97.73 wt%. The empirical formula (based on 18 O + Cl apfu) is: Pb2.88Cu5.922+Al0.07Te1.136+O6.59(OH)6.12Cl5.29. The ten strongest powder X-ray diffraction lines are [dobs in Å (hkl) I]: 6.106 (104) 44, 3.733 (0.0.12) 100, 2.749 (121) 53, 2.6686 (124) 49, 2.5289 (127) 41, 2.2772 (1.2.11) 38, 1.9637 (315, 1.2.16) 87, 1.8999 (multiple) 48, 1.5976 (multiple) 40, and 1.5843 (410, 1.2.23, 143) 44. The crystal structure of fuettererite (R1 = 0.031 for 971 reflections with Fo > 4σF) contains edge-sharing sheets of CuO5Cl and TeO6 octahedra. These sheets are virtually identical to that in the structure of spangolite, but in fuettererite they are linked together to form a double sheet. The double octahedral sheets alternate with thick double layers of PbO2Cl6 polyhedra. The CuO5Cl octahedra exhibit pronounced Jahn-Teller distortions and the PbO2Cl6 polyhedron has a lopsided distribution of bond lengths attributable to the localization of the Pb2+ 6s² lone-pair electrons. [ABSTRACT FROM AUTHOR]

Agaite, Pb3Cu2+Te6+O5(OH)2(CO3), is a new tellurate from the Aga mine on Otto Mountain near Baker, California, U.S.A. The new mineral is known from only one specimen. It occurs on quartz in association with cerussite, Br-rich chlorargyrite, chrysocolla, goethite, khinite, markcooperite, muscovite, phosphohedyphane, timroseite, and wulfenite. It is interpreted as having formed from the partial oxidation of primary sulfides and tellurides during or following brecciation of quartz veins. Agaite is orthorhombic, space group Pca21, with unit-cell dimensions a = 10.6522(7), b = 9.1630(5), c = 9.6011(7) Å, V = 937.12(11) Å3, and Z = 4. Agaite crystals form as blades flattened on {010} and probably elongated on [001], and are up to about 20 µm thick and 200 µm in length. The color is blue, the streak is pale blue, and the luster is adamantine. The Mohs hardness is estimated at between 2 and 3. Agaite is brittle with an irregular fracture and one perfect cleavage on {010}. The calculated density based on the empirical formula is 6.987 g/cm³. Agaite is biaxial (-), with calculated indices of refraction of α = 2.015, β = 2.065, and γ = 2.070°. The measured 2V is 34(5)° and the optical orientation is X = b, Y = c, and Z = a. It is pleochroic: X = pale blue, Y and Z = blue; X < Y = Z. Electron microprobe analyses (average of 4) provided: PbO 65.91, CuO 7.75, TeO3 17.41, CO2 4.33 (structure), H2O 1.78 (structure), total 97.18 wt%. The empirical formula (based on 10 O apfu) is: Pb3.00Cu0.992+Te1.016+O5(OH)2(CO3). The eight strongest powder X-ray diffraction lines are [dobs in Å (hkl) I]: 4.26 (012) 28, 4.165 (211) 14, 3.303 (022, 310, 221) 100, 2.7472 (131, 203, 312) 68, 2.571 (032, 401, 231) 14, 2.0814 (332, 422) 21, 2.0306 (511) 17, and 1.7468 (multiple) 40. The crystal structure of agaite (R1 = 0.033 for 1913 reflections with Fo > 4σF) contains edge-sharing chains of Cu2+O5 square pyramids and Te6+O6 octahedra parallel to a that are joined by corner-sharing in the c direction, forming a polyhedral sheet parallel to {010}. The polyhedral sheet is very similar to those in the structures of timroseite and paratimroseite. The thick interlayer region contains 8- and 9-coordinated Pb2+, as well as CO3 and OH groups. The Pb coordinations have lopsided distributions of bond lengths attributable to the localization of the Pb2+ 6s2 lone-pair electrons [ABSTRACT FROM AUTHOR]

The new mineral whelanite, Cu2Ca6 [Si6O17(OH)](CO3)(OH)3 (H2O)2, was approved by the Commission on New Minerals and Mineral Names (IMA) in 1977, but until now a description has not been published. The mineral is orthorhombic with space group Pn2n and cell parameters a = 5.6551(4), b = 3.683(3), c = 27.1372(7) Å, V = 565.3(5) ų, and Z = 1. The mineral occurs with thaumasite, stringhamite, and kinoite in a copper-rich, diopside-garnet-magnetite skarn at the Bawana mine, Beaver County, Utah, and has also been confirmed to occur at other localities. At the Bawana mine, it is found as irregular clusters and radial aggregates of platy to lath-like crystals up to 1 mm in length, flattened on {001} and elongated on [100]. The color and streak are pale blue and the luster is vitreous. The laths are flexible, but not elastic. Cleavage is perfect on {001} and good on {010}, producing splintery fracture. The Mohs' hardness is about 2 1/2. The measured density is 2.74(3) g/cm³ and the calculated density is 2.737 g/cm³ based upon the empirical formula. The mineral is biaxial (-), α = 1.612(2), β = 1.622(calc), and γ = 1.626(2), and 2Vmeas = 64(1)°. The pleochroism is weak: X = Y (pale blue) < Z (light blue). The optical orientation is X = a, Y = c, Z = b. A combination of electron microprobe analyses and thermogravimetric analyses (for CO2 and H2O) yielded: CaO 34.46, CuO 12.09, FeO 1.52, SiO2 37.96, CO2 5.93, H2O 8.86, total 100.82 wt%, providing the empirical formula (based on O = 26): Cu1.41Fe0.20Ca5.68Si5.84C1.25O26H9.09. Raman spectroscopy shows evidence of (CO3)2-, (OH)-, and H2O. The strongest powder X-ray diffraction lines are [d(hkl)I]: 6.79(004)52, 3.072(111)43, 3.013(112)100, 2.921(113)39, 2.802(114)45, 2.522(116,205)44, and 1.839(020,1.1.12)37. The crystal structure (R1 = 3.89% for 567 Fo > 4σF) contains two different types of polyhedral layers parallel to {001}, which alternate along [001] and are linked to one another by sharing corners with wollastonite-like silicate chains running parallel [010]. One polyhedral layer, consisting of edge-sharing CaO7 polyhedra, is identical to that in the structures of the tobermorites (tobermorite 9Å, tobermorite 11Å, tobermorite 14Å, and clinotobermorite). The other layer is brucite-like, with alternating ribbons of edge-sharing Cu2+O6 and CaO6 octahedra. Disordered CO3 and H2O groups are also located in the interlayer region. The crystal structure of whelanite exhibits OD character. [ABSTRACT FROM AUTHOR]

The crystal structures of the 3 R polytypes of takovite and woodallite are presented. The structure of takovite was solved on a single crystal from the Agoudal mine, Bou Azzer district, Tazenakht, Morocco to R1 = 1.87 % for 94 unique reflections [Fo4σF] in R3m, with unit cell parameters a = 3.0290(2) and c = 22.5995(15) Å. The crystal structure of woodallite [space group K3m, with unit cell parameters a = 3.10124(8) and c = 23.6817(16) Å] was refined utilising the Rietveld method on a sample from the MKD5 orebody at the Mount Keith Nickel Mine, Western Australia. [ABSTRACT FROM AUTHOR]

Metanatroautunite, Na[(UO2)(PO4)](H2O)3, from the Lake Boga granite, Victoria, Australia, has tetragonal symmetry, space group P4/ncc, with the unit-cell parameters: a = 6.9935(7), c = 17.5101(12) Å, V = 856.40(13) ų, and Z = 4. The crystal structure has been solved and refined to R1 = 0.0398 for 368 unique reflections [F > 4σ(F)] and 0.0456 for all 496 unique reflections. Metanatroautunite has an almost identical corrugated polyhedral sheet to meta-autunite-group minerals, consisting of corner-sharing uranyl square pyramids and phosphate tetrahedra. Hydrogen bonds (and cation-oxygen bonds) link the water molecules in the interlayer into square-planar sets, which are connected together creating 8-membered arrays. Metanatroautunite is identical to synthetic Na[(UO2)(PO4)](H2O)3. [ABSTRACT FROM AUTHOR]

Falsterite, ideally Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed., is a new mineral from the Palermo No. 1 pegmatite in North Groton, Grafton County, New Hampshire, U.S.A., and also occurs at the Estes pegmatite quarry, Baldwin, Cumberland County, Maine, U.S.A. It formed as the result of secondary alteration of primary triphylite and associated sphalerite. The crystals occur as very thin greenish-blue plates and rectangular laths, up to 0.7 mm in length, but no more than a few micrometers thick. Laths are flattened on {010}, elongate along [100], and exhibit lamellar twinning. The mineral is transparent and has a very pale greenish-blue streak, vitreous luster, Mohs hardness of about 2, flexible tenacity, irregular fracture, and perfect cleavage on {010}. The measured and calculated densities are 2.78(3) and 2.837 g/cm&#xsup3;, respectively. It is optically biaxial (--), α = 1.575(10),β = 1.600(5), γ = 1.610(5) (white light), 2Vmeas = 60(10), and 2Vcalc = 63.8. Falsterite exhibits strong dispersion, r > v. The optical orientation is X = b, Y ≈ a, Z ≈ c. Pleochroism is pronounced: X, Z = colorless to very pale yellow, Y = blue green; Y >> X ≈ Z. Electron-microprobe analyses (average of 7), with FeO and Fe2O3 apportioned and H2O calculated on structural grounds, provided: CaO 6.36, MgO 2.13, MnO 8.10, ZnO 18.49, FeO 8.02, Fe2O3 8.90, Al2O3 0.02, P2O5 31.81, H2O 16.17, total 100.00 wt%. The empirical formula (based on 50 O atoms) is Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. The mineral dissolves very easily in cold, dilute HC1. Falsterite is monoclinic, P21/c, with the unit-cell parameters: a = 6.3868(18), b = 21.260(7), c = 15.365(5) Å, β = 90.564(6), V = 2086.2(1.1) ų, and Z = 2. The eight strongest lines in the X-ray powder diffraction pattern are [dobs in Å(I)(hkl)]: 12.86(34)(011); 10.675(100)(020); 4.834(12)(102,ī12); 4.043(18)(ī32); 3.220(25)(ī52); 3.107(14)(044); 2.846(19)(2ֿ22); 1.596(14)(0·12·4). The structure of falsterite (R1 = 6.42% for 714 Fo > 4σF) contains edge-sharing chains of Fe2+/Fe3+O6 octahedra and corner-sharing chains of ZnO4 tetrahedra along [100]. These chains are linked to one another by PO4 tetrahedra, forming a sheet parallel to {010}. Mn2+O6 octahedra and CaO7 polyhedra also link to this sheet, resulting in a thick slab. The slabs are bridged in the [010] direction by edge-sharing dimers of MgO6 octahedra, which link to the slabs by sharing edges with ZnO4 tetrahedra in adjacent slabs. The structures of falsterite and schoonerite, while topologically quite different, share similar components and structural features. [ABSTRACT FROM AUTHOR]

We describe the first documented case of {101̅0} twinning by reflection (or by twofold rotation about [100]) or merohedry (class II) in a member of the apatite supergroup. Twinning about [100] had previously been noted for the apatite supergroup but not confirmed. Pyromorphite crystals from Puech de Compolibat, Combret, Aveyron, France, were studied by single-crystal X-ray diffraction [a = 10.0017(19), c = 7.3413(16) Å, and V = 636.0(2) ų, in P63/m], where twinning was confirmed with the approximate twin fraction 62:38. Subsequent inspection of the morphology confirmed the nature of the twinning. The pyromorphite crystals are typically elongate and show the faces: (21̅1̅0), (2̅110), (0001), (0001̅), (101̅0), (1̅010), (101̅2̅), and (1̅012̅). [ABSTRACT FROM AUTHOR]

Chromschieffelinite, Pb10Te6O20(OH) 14(CrO4)(H2O) 5, is a new tellurate from Otto Mountain near Baker, California, named as the chromate analog of schieffelinite, Pb10Te6O20(OH) 14(SO4)(H2O) 5. The new mineral occurs in a single 1 mm vug in a quartz vein. Associated mineral species include: chalcopyrite, chry socolla, galena, goethite, hematite, khinite, pyrite, and wulfenite. Chromschieffelinite is orthorhombic, space group C2221, a = 9.6646(3), b = 19.4962(8), c = 10.5101(7) Å, V= 1980.33(17) ų, and Z = 2. Crystals are blocky to tabular on {010} with striations parallel to [001]. The forms observed are {010}, {210}, {120}, {150}, {180}, {212}, and {101}, and crystals reach 0.2 mm in maximum dimension. The color and streak are pale yellow and the luster is adamantine. The Mohs hardness is estimated at 2. The new mineral is brittle with irregular fracture and one perfect cleavage on {010}. The calculated density based on the ideal formula is 5.892 g/cm³. Chromschieffelinite is biaxial (-) with indices of refraction α = 1.930(5), β = 1.960(5), and γ = 1.975(5), measured in white light. The measured 2V is 68(2)°, the dispersion is strong, r < v, and the optical orientation is X = b, Y = c, Z = a. No pleochroism was observed. Electron microprobe analysis provided: PbO 59.42, TeO3 29.08, CrO3 1.86, H2O 6.63 (structure), total 96.99 wt%; the empirical formula (based on 6 Te) is Pb9.65Te6O19.96(OH)14.04(CrO4)0.67(H2O)6.32. The strongest powder X-ray diffraction lines are [dobs in Å (hkl)I]: 9.814 (020) 100, 3.575 (042,202)41, 3.347 (222)44, 3.262 (241,060,113) 53, 3.052 (311) 45, 2.9455 (152,133) 55, 2.0396 (115,353) 33, and 1.6500 (multiple) 33. The crystal structures of schieffelinite (R1 = 0.0282) and chromschieffelinite (R1 = 0.0277) contain isolated Te6+O6 octahedra and TeDue to image rights restrictions, multiple line equation(s) cannot be graphically displayed.O11 corner-sharing dimers, which are linked into a three-dimensional framework via bonds to Pb2+ atoms. The framework has large channels along c, which contain disordered SO4 or CrO4 groups and H2O. The lone- electron pair of each Pb2+ is stereochemically active, resulting in one-sided Pb-O coordination arrangements. The short Pb-O bonds of the Pb2+ coordinations are all to Te6+O6 octahedra, resulting in strongly bonded layers parallel to {010}, which accounts for the perfect {010} cleavage. [ABSTRACT FROM AUTHOR]

The crystal structures of the tellurite minerals juabite, CaCu10(Te4+O3)4 (AsO4)4(OH)2(H2O)4, poughite, Fe3+ 2(Te4+O3)2(SO4) (H2O) 2⋅H2O and rodalquilarite, Fe3+ 2(Te4+O2OH) 3 (Te4+O3)Cl, have been refined to R1 (Fo > 4σF) = 2.36%, 2.38% and 1.84%, respectively. The determination of H atom positions in all three structures has allowed the elucidation of the hydrogen bonding schemes and detailed bond-valence analyses. These are the only tellurite mineral structures for which H atom positions have been determined. The structures of all contain one-sided Te4+ coordinations as Te4+O3 pyramids with additional anions at greater distances. The one-sided coordinations are attributable to the stereochemically active 6s⊃2 lone-electron-pair of the Te4+. The overall linkage schemes in these structures are quite different, yet all can be considered layer structures in which relatively weak long Te-0 and/or Te-Cl bonds are involved in the linkages between layers. In juabite, a long apical Cu-O bond participates in the linkage between layers and, in poughite and rodalquilarite, hydrogen bonding also links the layers. [ABSTRACT FROM AUTHOR]

Abstract: Yb2(SO4)3·3H2O, synthesised by hydrothermal methods at 220(2)°C, has been investigated by single crystal X-ray diffraction. Yb2(SO4)3·3H2O crystallises in space group Cmc21 and is isostructural with Lu2(SO4)3·3H2O. The crystal structure has been refined to R 1=0.0145 for 3412 reflections [F o >3σ(F)], and 0.0150 for all 3472 reflections. The structure of Yb2(SO4)3·3H2O is a complex framework of YbO6 octahedra, YbO8 and YbO5(H2O)3 polyhedra and SO4 tetrahedra. Thermal data shows that Yb2(SO4)3·3H2O decomposes between 120 and 190°C to form β-Yb2(SO4)3. The structure of a twinned crystal of β-Yb2(SO4)3 was solved and refined using an amplimode refinement in R3c with an R 1=0.0755 for 8944 reflections [F o >3σ(F)], and 0.1483 for all 16,361 reflections. β-Yb2(SO4)3 has a unique structural topology based on a 3D network of pinwheels. [Copyright &y& Elsevier]

Yttriaite-(Y), ideally Y2O3, is a new mineral (IMA2010-039) from the alluvial deposits of the Bol'shaya Pol'ya River, Subpolar Urals, Russia. The new mineral occurs as isolated crystals, typically cubo-octahedra <6 µm in size, embedded in massive native tungsten. Associated minerals include: copper, zircon, osmium, gold, and pyrite. The main forms observed are {100} and {111}. Due to the crystal size, physical properties could not be determined; however, the properties of synthetic Y2O3 are well known. Synthetic Y2O3 crystals are colorless to white with a white streak; crystals are transparent with an adamantine luster, while massive Y2O3 is typically translucent with an earthy luster. Synthetic Y2O3 has a Vickers hardness of 653.91, which corresponds to 5.5 on the Mohs scale. Synthetic Y2O3 crystals have good cleavage on {111}. Yttriaite-(Y) is isotropic; the refractive index measured at 587 nm on synthetic Y2O3 is n = 1.931. The empirical chemical formula (mean of 4 electron microprobe analyses) calculated on the basis of 3 O is: Y1.98Dy0.01Yb0.01O3. Yttriaite-(Y) is cubic, space group Ia3̄, with parameters a = 10.6018(7) Å, V = 1191.62(7) ų, and Z = 16. The five strongest lines in the powder X-ray diffraction pattern (measured on synthetic Y2O3 using synchrotron radiation) are [dobs in Å (I) (hkl)]: 3.0646 (100) (222), 1.8746 (55) (440), 1.5984 (38) (622), 2.6537 (26) (400), and 4.3356 (14) (211). The mineral name is based on the common name for the chemical compound, yttria. [ABSTRACT FROM AUTHOR]

Stichtite, ideally Mg6Cr2CO3(OH)16⋅4H2O, from Stichtite Hill, Tasmania, Australia, and barbertonite, also ideally Mg6Cr2CO3(OH)16⋅4H2O, from the Kaapsehoop asbestos mine, South Africa, have been studied by powder X-ray diffraction and their structures have been refined using the Rietveld method. Stichtite from Stichtite Hill crystallizes in the rhombohedral space group R3̄m, with unit-cell parameters a = 3.09575(3) and c = 23.5069(6) Å, V = 195.099(6) ų, with Z = 3/8. Barbertonite from the Kaapsehoop asbestos mine crystallizes in the hexagonal space group P63/mmc. The co-type specimens of barbertonite were found to be intergrown mixtures consisting of barbertonite and stichtite. Unit-cell parameters of barbertonite from the co-type specimens were a = 3.09689(6), c = 15.6193(8) Å, and V = 129.731(8) ų and a = 3.09646(6), c = 15.627(1) Å V = 129.76(1) ų, and Z = 1/4. Rietveld refinements of both stichtite and barbertonite show that they are polytypes rather than polymorphs and do not represent distinct mineral species. Several possible nomenclature systems are discussed for the naming of hydrotalcite minerals and groups. Raman band assignments are also presented for stichtite from Stichtite Hill. Stichtite and hydrotalcite minerals make up a large proportion of the ore at the Mount Keith nickel mine in Western Australia. Bulk powder diffraction shows the ore contains 6.1 wt% stichtite and 5.6 wt% iowaite. Hydrotalcite group minerals provide an important potential reservoir of CO2. At Mount Keith, the amount of CO2 mined as stichtite could exceed 45 000 metric tons per year, while exchange of Cl for CO3 could fix in excess of 40 000 metric tons CO2 per year if end-member iowaite is reacted to form pyaroaurite. [ABSTRACT FROM AUTHOR]

Auriacusite, ideally Fe3+Cu2+AsO4O, is a new arsenate mineral (IMA2009–037) and the Fe3+ analogue of olivenite, from the Black Pine mine, 14.5 km NW of Philipsburg, Granite Co., Montana, USA. It occurs lining quartz vughs and coating quartz crystals and is associated with segnitite, brochantite, malachite, tetrahedrite and pyrite. Auriacusite forms fibrous crystals up to about 5 µm in width and up to about 100 µm in length, which are intergrown to form fibrous mats. Individual crystals are a brownish golden yellow, whilst the fibrous mats are ochreous yellow. The crystals have a silky lustre and a brownish yellow streak. Mohs hardness is about 3 (estimated). The fracture is irregular and the tenacity is brittle. Auriacusite crystals are biaxial (+), with α = 1.830(5), β = 1.865(5) and γ = 1.910(5), measured using white light, and with 2 Vmeas. = 83(3)º and 2 Vcalc. = 84.6º. Orientation: X = a, Y = c, Z = b. Crystals are nonpleochroic or too weakly so to be observed. The empirical formula (based on 5 O atoms) is (FeCu0.85Zn0.03)Σ2.21(As0.51Sb0.27Si0.04 S0.02Te0.01)Σ0.85O5. Auriacusite is orthorhombic, space group Pnnm, a = 8.6235(7), b = 8.2757(7), c = 5.9501(5) Å, V = 424.63(6) Å3, Z = 4. The five strongest lines in the powder X-ray diffraction pattern are [ dobs in Å / ( I) / hkl]: 4.884 / (100) / 101, 001; 2.991 / (92) / 220; 2.476 / (85) / 311; 2.416 / (83) / 022; 2.669 / (74) / 221. The crystal structure was solved from single-crystal X-ray diffraction data utilising synchrotron radiation and refined to R1 = 0.1010 on the basis of 951 unique reflections with Fo > 4σ F. Auriacusite is identified as a member of the olivenite group with Fe3+ replacing Zn2+ or Cu2+ in trigonal bipyramidal coordination. Evidence suggests that auriacusite is an intermediate member between olivenite and an as yet undescribed Fe3+Fe3+-dominant member. The name is derived from the Latin auri (golden yellow) and acus (needle), in reference to its colour and crystal morphology. [ABSTRACT FROM AUTHOR]

The results are presented of Gibbs ensemble Monte Carlo (GEMC) simulations examining the nematic-isotropic (N-I) coexistence envelope of a liquid crystal mixture. The system studied is a 50:50 mixture of 1000 generalized Gay-Berne particles with axial ratios 2.0:1 and 2.5:1. For this system, stable N-I coexistence is observed over run lengths in excess of 5 x 10[sup 5] GEMC sweeps. There is unambiguous evidence of fractionation, the mole fractions of long particles in the coexisting phases typically differing by 11%. The measured coexistence envelope does not conform to the lens shape predicted by Onsager theory; qualitative finite size arguments are given in explanation of this distortion. [ABSTRACT FROM AUTHOR]