Bountiful, UT, United States
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Kasatkin A.V.,Russian Academy of Sciences | Plasil J.,ASCR Institute of Physics Prague | Pekov I.V.,Moscow State University | Belakovskiy D.I.,Russian Academy of Sciences | And 5 more authors.
Journal of Geosciences (Czech Republic) | Year: 2015

Karpenkoite (IMA 2014-092), ideally Co3(V2O7)(OH)2·2H2O, is a new divanadate mineral species, the cobalt analogue of martyite, found at the Little Eva mine, Grand County, Utah, USA. It occurs on sandstone matrix in close association with martyite, quartz, gypsum, baryte, roscoelite and an unidentified Al vanadate. Karpenkoite is a secondary mineral formed during the post-mining oxidation of corvusite and montroseite in a moist environment at ambient temperatures. The new mineral occurs as lamellar crystals, coarsely hexagonal or irregular in shape, typically curved. The crystals form rose-like clusters or globular aggregates up to 0.2 mm across. Karpenkoite is orange with pale yellow-orange streak. It is transparent with a vitreous luster. The mineral is brittle, with laminated fracture and perfect cleavage on {001}. The calculated density is 3.415 g cm-3. The mineral is optically uniaxial (+), with ω = 1.827(8) and ε = 1.843(8). The chemical composition of karpenkoite (wt. %, electron-microprobe data) is: MgO 0.05, CaO 0.26, MnO 1.39, CoO 33.22, NiO 2.02, CuO 0.28, ZnO 12.66, V2O5 38.70, H2O (calc.) 11.61, total 100.19. The empirical formula, calculated on the basis of 11 O apfu, is (Co2.06Zn0.72Ni0.13Mn0.09Ca0.02Cu0.02Mg0.01)Σ3.05V1.98O7(OH)2·2H2O. The Raman spectrum demonstrates symmetric stretching and bending vibrations of V5+O3 units and the O–H stretching and bending vibrations of the H2O molecules. The new mineral is trigonal, the most probable space group is (Formula presented.) (by analogy with its Zn analogue martyite), a = 6.016(4), c = 7.234(6) Å, V = 226.7(2) Å3 and Z = 1. The strongest powder X-ray diffraction lines are [dobs,Å(I)(hkl)]: 7.15(100)(001), 5.19(18)(010), 4.20(25)(101,011), 3.59(21)(002), 2.95(54)(012,102), 2.77(21)(111), 2.60(36)(200), and 2.44(33)(201,021). The new mineral is named in honor of the Russian mineralogist Vladimir Yu. Karpenko (b. 1965), an expert on the mineralogy of vanadium. © 2015, Czech Geological Society. All Rights Reserved.


Kampf A.R.,Natural History Museum of Los Angeles County | Mills S.J.,Khan Research Laboratories | Housley R.M.,California Institute of Technology | Rossman G.R.,California Institute of Technology | And 2 more authors.
American Mineralogist | Year: 2013

Eckhardite, (Ca,Pb)Cu2+Te6+O5(H 2O), is a new tellurate mineral from Otto Mountain near Baker, California, USA. 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 monoclinic, 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) Å3, and Z = 4. It forms as needles or blades up to about 150 × 15 × 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 α = 1. 770 (calc), β = 1.860 (calc), and γ = 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) < X (colorless). The normalized electron microprobe analyses (average of 4) provided: PbO 4.79, CaO 15.90, MgO 0.06, CuO 22.74, Fe2O3 0.06, TeO3 51.01, H 2O 5.45 (structure), total 100 wt%. The empirical formula (based on 6 O apfu) is: Ca0.962Pb0.073Cu0.971 2+Mg0.005Fe0.002 3+Te 0.986 6+ O6H2.052. The Raman spectrum exhibits prominent features consistent with the mineral being a tellurate, as well as an OH stretching feature confirming a hydrous component. The eight strongest powder X ray diffraction lines are [dobs in Å (hkl) I]: 5.94 (101) 100, 3.287 (112) 80, 2.645 (020,2̄13) 89, 2.485 (1̄14,301,014) 48, 2.245 (114,122) 46, 1.809 (223,413,321,4̄04) 40, 1.522 (413,5̄12,421,133) 42, and 1.53 (2̄17,2̄33,4̄06) 43. The crystal structure of eckhardite (R1 = 0.046 for 586 reflections with Fo > 4σF) consists of stair-step-like octahedral layers of Te6+O6 and Cu2+O6 octahedra parallel to {101}, which are linked in the [101̄] 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.


Kampf A.R.,Natural History Museum of Los Angeles County | Mills S.J.,Khan Research Laboratories | Housley R.M.,California Institute of Technology | Rossman G.R.,California Institute of Technology | And 2 more authors.
American Mineralogist | Year: 2013

Bairdite, Pb2Cu4 2+Te2 6+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/cm 3. 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: Pb2.05Ca0.01Cu3.99 2+Te2.00 6+S0.96O 17.00H4.16. 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 > 4δF) contains edge-sharing chains of Te 6+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.


Mills S.J.,Khan Research Laboratories | Kampf A.R.,Natural History Museum of Los Angeles County | Christy A.G.,Australian National University | Housley R.M.,California Institute of Technology | And 3 more authors.
European Journal of Mineralogy | Year: 2014

Favreauite, ideally PbBiCu6O4(SeO3)4(OH) · H2O, is a new secondary selenite mineral from the El Dragón mine, Antonio Quijarro Province, Potosí Department, Bolivia. The mineral occurs in vughs in a matrix of (Co, Cu)-rich penroseite, dolomite and goethite. Associated minerals are: ahlfeldite, allophane, calcite, chalcomenite, malachite, molybdomenite and an unnamed Al selenite. Favreauite forms tiny green square tabular crystals, flattened on {001}, up to 0.1 mm on edge and 0.01 mm thick, occurring in subparallel and divergent groups. The Mohs hardness of favreauite is estimated as ≈:3; it has perfect cleavage on {001}, an irregular fracture and a vitreous lustre. The calculated density based on the empirical formula is 4.851 g cm-3. Favreauite is uniaxial (-), with mean refractive index estimated as 1.854 from the Gladstone-Dale relationship. It is pleochroic in shades of green, O < E. Electron microprobe analyses gave the empirical formula Pb0.95Ca0.17Bi0.90Cu5.81Se4.10O16(OH) · 1H2O, based on 18 O pfu. The Raman spectrum shows strong SeO3 bands at 847 cm-1 (v1), 764 and 795 cm-1 (v3), 493 and 542 cm-1 (v2), and 320 and 392 cm-1 (v4). Favreauite is tetragonal, space group P4/n, with the unit-cell parameters: a = 9.860(4) Å, c = 9.700(5) Å, V= 943.0(9) Å3 and Z= 2. The eight strongest lines in the X-ray powder diffraction pattern are [dobs/Å (I) (hkl)]: 5.67(100)(111), 3.470(76)(220,202), 3.190(35)(003), 2.961(40)(311,113), 2.709(33)(302,203), 2.632(34)(231,312), 2.247(36)(331,133), and 1.6652(33)(305,513,531). The crystal structure was refined to R1 = 0.0329 for 1354 observed reflections [Fo > 4σFo] and 0.0356 for all 1432 unique reflections. Favreauite is a close structural relative of nabokoite, KCu7Te4+O4(SO4)5Cl, and atlasovite, KCu6Fe3+BiO4(SO4)5Cl. In all cases, oxygen-centred tetrahedra share edges to form corrugated [Cu6MO4] layers (M = Bi or Te) which can be derived from the framework structure of murdochite, Pb4+Cu2 + 6O8-x(Cl,Br)2x by selective deletion of atoms. In favreauite, additional OH and H2O between the layers are weakly bound to Cu, giving it Jahn-Teller distorted 4 + 2 coordination. The Cu-Bi-O layer is braced by SeO3 pyramids. The Bi3+ and interlayer Pb2+ form an approximately face-centred cubic array analogous to the Pb4+ sites in murdochite. Unlike Bi3+, Pb2+ is in a site with nonpolar 4 point symmetry, which suppresses the stereoactivity of its lone pair. © 2014 E. Schweizerbart'sche Verlagsbuchhandlung, D-70176 Stuttgart.


Kampf A.R.,Natural History Museum of Los Angeles County | Mills S.J.,University of British Columbia | Housley R.M.,California Institute of Technology | Mararty J.,3457 E. Silver Oak Road | Thorne B.,3898 S. Newport Circle
American Mineralogist | Year: 2010

Markcooperite, Pb2(UO2)Te6+O6, is a new tellurate from Otto Mountain near Baker, California, named in honor of Mark A. Cooper of the University of Manitoba for his contributions to mineralogy. The new mineral occurs on fracture surfaces and in small vugs in brecciated quartz veins. Markcooperite is directly associated with bromian chlorargyrite, iodargyrite, khinite-4O, wulfenite, and four other new tellurates: housleyite, thorneite, ottoite, and timroseite. Various other secondary minerals occur in the veins, including two other new secondary tellurium minerals: paratimroseite and telluroperite. Markcooperite is monoclinic, space group P21/c, a = 5.722(2), b = 7.7478(2), c = 7.889(2) Å, β = 90.833(5)°, V = 349.7(2) Å3, and Z = 2. It occurs as pseudotetragonal prisms to 0.2 mm with the forms {100} and {011} and as botryoidal intergrowths to 0.3 mm in diameter; no twinning was observed. Markcooperite is orange and transparent, with a light orange streak and adamantine luster, and is non-fluorescent. Mohs hardness is estimated at 3. The mineral is brittle, with an irregular fracture and perfect {100} cleavage. The calculated density is 8.496 g/cm3 based on the empirical formula. Markcooperite is biaxial (+), with indices of refraction a = 2.11, β = 2.12, ? = 2.29 calculated using the Gladstone-Dale relationship, measured a-β birefringence of 0.01 and measured 2V of 30(5)°. The optical orientation is X = c, Y = b, Z = a. The mineral is slightly pleochroic in shades of orange, with absorption: X > Y = Z. No dispersion was observed. Electron microprobe analysis provided PbO 50.07, TeO3 22.64, UO3 25.01, Cl 0.03, O=Cl -0.01, total 97.74 wt%; the empirical formula (based on O+Cl = 8) is Pb2.05U0.80Te6+ 1.18O7.99Cl0.01. The strongest powder X-ray diffraction lines are [dobs in Å (hkl) I]: 3.235 (120, 102, 102) 100, 2.873 (200) 40, 2.985 (121, 112, 121) 37, 2.774 (022) 30, 3.501 (021, 012) 29, 2.220 (221, 221, 212) 23, 1.990 (222, 222) 21, and 1.715 (320) 22. The crystal structure (R1 = 0.052) is based on sheets of corner-sharing uranyl square bipyramids and tellurate octahedra, with Pb atoms between the sheets. Markcooperite is the first compound to show Te6+ substitution for U6+ within the same crystallographic site. Markcooperite is structurally related to synthetic Pb(UO2)O2.


Kampf A.R.,Natural History Museum of Los Angeles County | Mills S.J.,University of British Columbia | Housley R.M.,California Institute of Technology | Mararty J.,3457 E. Silver Oak Road | Thorne B.,3898 S. Newport Circle
American Mineralogist | Year: 2010

Telluroperite, Pb3Te4+O4Cl2, is a new tellurite from Otto Mountain near Baker, California. The new mineral occurs on fracture surfaces and in small vugs in brecciated quartz veins in direct association with acanthite, bromine-rich chlorargyrite, caledonite, cerussite, galena, goethite, and linarite. Various other secondary minerals occur in the veins, including six new tellurates, housleyite, markcooperite, paratimroseite, ottoite, thorneite, and timroseite. Telluroperite is orthorhombic, space group Bmmb, a = 5.5649(6), b = 5.5565(6), c = 12.4750(14) Å, V = 386.37(7) Å3, and Z = 2. The new mineral occurs as rounded square tablets and flakes up to 0.25 mm on edge and 0.02 mm thick. The form {001} is prominent and is probably bounded by {100}, {010}, and {110}. It is bluish-green and transparent, with a pale bluish-green streak and adamantine luster. The mineral is non-fluorescent. Mohs hardness is estimated to be between 2 and 3. The mineral is brittle, with a curved fracture and perfect {001} cleavage. The calculated density based on the empirical formula is 7.323 g/cm3. Telluroperite is biaxial (-), with very small 2V (̃10°). The average index of refraction is 2.219 calculated by the Gladstone-Dale relationship. The optical orientation is X = c and the mineral exhibits moderate bluish-green pleochrosim; absorption: X < Y = Z. Electron microprobe analysis provided PbO 72.70, TeO2 19.26, Cl 9.44, O=Cl -2.31, total 99.27 wt%. The empirical formula (based on O+Cl = 6) is Pb2.79Te4+ 1.03O3.72Cl2.28. The six strongest powder X-ray diffraction lines are [dobs in Å (hkl) I]: 3.750 (111) 58, 2.857 (113) 100, 2.781 (020, 200) 43, 2.075 (024, 204) 31, 1.966 (220) 30, and 1.620 (117, 313, 133) 52. The crystal structure (R1 = 0.056) is based on the Sillén X1 structure-type and consists of a three-dimensional structural topology with lead-oxide halide polyhedra linked to tellurium/lead oxide groups. The mineral is named for the relationship to perite and the dominance of Te (with Pb) in the Bi site of perite.


Kampf A.R.,Natural History Museum of Los Angeles County | Mills S.J.,University of British Columbia | Housley R.M.,California Institute of Technology | Mararty J.,3457 E. Silver Oak Road | Thorne B.,3898 S. Newport Circle
American Mineralogist | Year: 2010

Timroseite, Pb2Cu52+(Te6+O 6)2(OH)2, and paratimroseite, Pb 2Cu4 2+(Te6+O6) 2(H2O)2, are two new tellurates from Otto Mountain near Baker, California. Timroseite is named in honor of Timothy (Tim) P. Rose and paratimroseite is named for its relationship to timroseite. Both new minerals occur on fracture surfaces and in small vugs in brecciated quartz veins. Timroseite is directly associated with acanthite, cerussite, bromine-rich chlorargyrite, chrysocolla, gold, housleyite, iodargyrite, khinite-4O, markcooperite, ottoite, paratimroseite, thorneite, vauquelinite, and wulfenite. Paratimroseite is directly associated with calcite, cerussite, housleyite, khinite-4O, markcooperite, and timroseite. Timroseite is orthorhombic, space group P21nm, a = 5.2000(2), b = 9.6225(4), c = 11.5340(5) Å, V = 577.13(4) Å3, and Z = 2. Paratimroseite is orthorhombic, space group P212121, a = 5.1943(4), b = 9.6198(10), c = 11.6746(11) Å, V = 583.35(9) Å3, and Z = 2. Timroseite commonly occurs as olive to lime green, irregular, rounded masses and rarely in crystals as dark olive green, equant rhombs, and diamond-shaped plates in subparallel sheaf-like aggregates. It has a very pale yellowish green streak, dull to adamantine luster, a hardness of about 2= (Mohs), brittle tenacity, irregular fracture, no cleavage, and a calculated density of 6.981 g/cm3. Paratimroseite occurs as vibrant "neon" green blades typically intergrown in irregular clusters and as lime green botryoids. It has a very pale green streak, dull to adamantine luster, a hardness of about 3 (Mohs), brittle tenacity, irregular fracture, good {001} cleavage, and a calculated density of 6.556 g/cm3. Timroseite is biaxial (+) with a large 2V, indices of refraction < 2, orientation X = b, Y = a, Z = c and pleochroism: X = greenish yellow, Y = yellowish green, Z = dark green (Z < Y < X). Paratimroseite is biaxial (-) with a large 2V, indices of refraction < 2, orientation X = c, Y = b, Z = a and pleochroism: X = light green, Y = green, Z = green (Y = Z >> X). Electron microprobe analysis of timroseite provided PbO 35.85, CuO 29.57, TeO3 27.75, Cl 0.04, H2O 1.38 (structure), O=Cl -0.01, total 94.58 wt%; the empirical formula (based on O+Cl = 14) is Pb2.07 Cu2+ 4.80Te 6+ 2.04O12(OH)1.98Cl0.02. Electron microprobe analysis of paratimroseite provided PbO 36.11, CuO 26.27, TeO3 29.80, Cl 0.04, H2O 3.01 (structure), O=Cl -0.01, total 95.22 wt%; the empirical formula (based on O+Cl = 14) is Pb 1.94Cu2+ 3.96Te6+ 2.03O12(H2O)1.99Cl0.01. The strongest powder X-ray diffraction lines for timroseite are [dobs in Å (hkl) I]: 3.693 (022) 43, 3.578 (112) 44, 3.008 (023) 84, 2.950 (113) 88, 2.732 (130) 100, 1.785 (multiple) 33, 1.475 (332) 36; and for paratimroseite 4.771 (101) 76, 4.463 (021) 32, 3.544 (120) 44, 3.029 (023,122) 100, 2.973 (113) 48, 2.665 (131) 41, 2.469 (114) 40, 2.246 (221) 34. The crystal structures of timroseite (R1 = 0.029) and paratimroseite (R1 = 0.039) are very closely related. The structures are based upon edge- and corner-sharing sheets of Te and Cu polyhedra parallel to (001) and the sheets in both structures are identical in topology and virtually identical in geometry. In timroseite, the sheets are joined to one another along c by sharing the apical O atoms of Cu octahedra, as well as by sharing edges and corners with an additional CuO5 square pyramid located between the sheets. The sheets in paratimroseite are joined only via Pb-O and H bonds.


Christy A.G.,Australian National University | Kampf A.R.,Natural History Museum of Los Angeles County | Mills S.J.,Khan Research Laboratories | Housley R.M.,California Institute of Technology | Thorne B.,3898 S. Newport Circle
Mineralogical Magazine | Year: 2014

The crystal structure of burckhardite from the type locality, Moctezuma, Sonora, Mexico, has been refined to R 1 = 0.0362 and wR 2 = 0.0370 for 215 reflections with I > 2σ(I). Burckhardtite is trigonal, space group P31m, with the unit-cell parameters a = 5.2566(5) Å, c = 13.0221(10) Å, V = 311.62(5) Å3 and Z = 1 for the ideal formula unit Pb2(Fe3+Te6+)[AlSi3O8]O6. There is no long-range order of (Fe3+, Te6+) or (Al3+, Si4+). New microprobe data were used to estimate site scattering factors, and Raman spectroscopic data showed no evidence of O-H stretching bands. Burckhardtite is not closely related to the micas, as supposed previously, but is a double-sheet silicate in which the aluminosilicate anion resembles that of minerals such as cymrite and kampfite. The [(Fe3+Te6+)O6]3- part of the structure is not bonded directly to the aluminosilicate layer, but forms a discrete anionic phyllotellurate layer that alternates with the [AlSi3O8]- double sheets. Similar phyllotellurate layers are known from several synthetic phases. In burckhardtite, Pb2+ cations intercalate between phyllosilicate and phyllotellurate layers, forming a Pb2[FeTeO6] module that is topologically similar to a slab of the structure of rosiaite, Pb[Sb2O6]. The crystal symmetry, structure, classification as a double-sheet silicate and chemical formula, including the determination of the 6+ valence of Te and absence of essential H2O, are all new findings for the mineral. © 2014 Mineralogical Society.


Kampf A.R.,Natural History Museum of Los Angeles County | Mararty J.,3457 E. Silver Oak Road | Thorne B.,3898 S. Newport Circle
American Mineralogist | Year: 2010

Housleyite, Pb6CuTe4O18(OH)2, is a new tellurate from Otto Mountain near Baker, California, named in honor of Robert M. Housley. The new mineral occurs on fracture surfaces and in small vugs in brecciated quartz veins. Housleyite is directly associated with acanthite, cerussite, gold, iodargyrite, khinite-4O, wulfenite, and three other new tellurates: Markcooperite, ottoite, and thorneite. A variety of other secondary minerals occur in the veins, including three other new secondary tellurium minerals, paratimroseite, telluroperite, and timroseite. Housleyite is monoclinic, space group P21/n, a = 7.8552(5), b = 10.4836(7), c = 11.0426(8) Å, bβ = 95.547(2)°, and Z = 2. Crystals are prismatic to bladed with elongation parallel to b and typically occur in bow tie-like aggregates, drusy balls, and irregular sprays. It is pale to medium greenish blue and transparent, with pale blue streak and adamantine luster. Mohs hardness is estimated at 3. The mineral is brittle, with an irregular fracture. Cleavage was not observed, but is likely on {101}. The calculated density is 7.845(1) g/cm3. Housleyite is biaxial (+), with 2V = 50° to 60° and strong inclined dispersion, r > v, but indices of refraction are too high to be measured. The optic orientation is Y = b, Z ^ c ≈40° in obtuse β and pleochroism is Y (medium green-blue) > Z (light green-blue) > X. Energy dispersive spectroscopy provided PbO 62.53, CuO 3.77, TeO3 32.85, H3O 0.84 (structure), total 99.99 wt%.; the empirical formula (based on O = 20) is b5.99Cu1.01Te4.00O 18(OH)2. The strongest powder X-ray diffraction lines are [dobs in Å (hkl) I]: 3.336 (202, 031, 122) 69, 3.292 (113) 50, 3.195 (130, 103) 100, 3.068 (221, 202) 47, 3.007 (023) 49, 2.942 (032, 212) 80, 2.723 (123, 213, 132) 29, 2.580 (230, 301, 231) 38. The crystal structure (R1 = 0.028) consists of corner-sharing chains of TeO6 octahedra along [101] linked into slabs parallel to {101} by sharing edges and corners with strongly Jahn-Teller (4+2) distorted and severely skewed CuO 6 octahedra. Lead (Pb) atoms in lopsided nine- and elevenfold coordinations form additional links within and between the octahedral sheets.


Kampf A.R.,Natural History Museum of Los Angeles County | Mills S.J.,Khan Research Laboratories | Nash B.P.,University of Utah | Thorne B.,3898 S Newport Circle | Favreau G.,421 Avenue Jean Monnet
European Journal of Mineralogy | Year: 2016

Alfredopetrovite, Al2(Se4+O3)3·6H2O, is a new secondary selenite mineral from the El Dragón mine, Antonio Quijarro Province, Potosí Department, Bolivia. The mineral occurs in vugs in a matrix of Co-rich krut'aite-penroseite, dolomite and goethite. Associated minerals are: ahlfeldite, allophane, calcite, chalcomenite, favreauite, felso{combining double acute accent}bányaite, malachite and molybdomenite. Crystals occur in drusy/scaly coatings and compact balls, the latter to 0.5 mm in diameter. Individual crystals are up to about 0.1 mm across. The Mohs hardness of alfredopetrovite is 2 1/2; it has no cleavage, curved fracture and a vitreous lustre. The calculated density based on the empirical formula is 2.504 g cm-3. Alfredopetrovite is uniaxial (+), with ω = 1.554(2) and ε = 1.566(2) (white light), and exhibits no pleochroism. Electron microprobe analyses gave the empirical formula Al1.94Cu0.07Ni0.03Co0.01Se2.95O15H12.16, based on 15 O apfu. Alfredopetrovite is hexagonal, space group P62c, with the unit-cell parameters: a = 8.818(3) Å, c = 10.721(2) Å, V = 722.0(5) Å3 and Z = 2. The eight strongest lines in the X-ray powder diffraction pattern are [dobs/Å (I) (hkl)]: 7.63(55)(100), 6.22(55)(101), 5.37(26)(002), 4.398(40)(110,102), 3.404(100)(112), 2.783(50)(211), 2.606(22)(203), and 1.6609(26)(410,322,314,116). The crystal structure was refined to R1 = 0.0268 for 240 observed reflections [Fo > 4σF]. The structure is comprised of fairly regular AlO6 octahedra and Se4+O3 triangular pyramids. Three Se4+O3 pyramids link two adjacent AlO6 octahedra forming a [Al(H2O)3]2(Se4+O3)3 cluster structural unit. These structural units are bonded to one another only via hydrogen bonds yielding a structure with relatively large channels along [001]. The configuration of the cluster is similar to that of the distinctive unit in the NASICON structure, commonly referred to as a lantern unit. © 2015 E. Schweizerbart'sche Verlagsbuchhandlung.

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