Sveinbergeite, Ca(Fe2+6 Fe3+)Ti2(Si4O12)2O2(OH)5(H2O)4, a new astrophyllite-group mineral from the Larvik Plutonic Complex, Oslo Region, Norway: description and crystal structure

2011 ◽  
Vol 75 (5) ◽  
pp. 2687-2702 ◽  
Author(s):  
A. P. Khomyakov ◽  
F. Cámara ◽  
E. Sokolova ◽  
Y. Abdu ◽  
F. C. Hawthorne
Keyword(s):  
Crystal Structure ◽  
Manganese Oxides ◽  
Structure Refinement ◽  
Direct Methods ◽  
Calculated Density ◽  
Group Mineral ◽  
Amateur Mineralogist ◽  
Perfect Cleavage ◽  
Mohs Hardness ◽  
Deep Green

AbstractSveinbergeite, Ca(Fe2+6Fe3+)Ti2(Si4O12)2O2(OH)5(H2O)4, is a new astrophyllite-group mineral discovered in a syenite pegmatite at Buer on the Vesteroya peninsula, Sandefjord, Oslo Region, Norway. The mineral occurs in pegmatite cavities as 0.01—0.05 mm thick lamellar (0.2—0.5×5—10 mm) crystals forming rosette-like divergent groups and spherical aggregates, which are covered by brown coatings of iron (and possibly manganese) oxides, associated with magnesiokatophorite, aegirine, microcline, albite. calcite, fluorapatite, molybdenite, galena and a hochelagaite-like mineral. Crystals of sveinbergeite are deep green with a pale green streak and a vitreous and pearly lustre. Sveinbergeite has perfect cleavage on ﹛001﹜ and a Mohs hardness of 3. Its calculated density is 3.152 g/cm3. It is biaxial positive with α 1.745(2), β 1.746(2), γ 1.753(2), 2V(meas.) = 20(3)°. The mineral is pleochroic according to the scheme Z > X ∽ Y : Z is deep green, X and Y are brownish green. Orientation is as follows: X ┴ L (001), Y ᶺ b = 12°, Z = a, elongation positive. Sveinbergeite is triclinic, space group P1̄, a = 5.329(4), b = 11.803(8), c = 11.822(8) Å; α = 101.140(8)°, β = 98.224(8)°, γ = 102.442(8)°; V = 699.0(8) Å3; Z = 1. The nine strongest lines in the X-ray powder diffraction pattern [d in Å(I)(hkl)] are: 11.395(100)(001,010). 2.880(38)(004), 2.640(31)(2̄10,l̄41), 1.643(24)(07̄1,072), 2.492(20)(2l̄l), 1.616(15)(070), 1.573(14)(3̄2̄2), 2.270(13)(1̄3̄4) and 2.757(12)(1̄40,1̄3̄2). Chemical analysis by electron microprobe gave Nb2O5 0.55, TiO2 10.76, ZrO2 0.48, SiO2 34.41, A12O3 0.34, Fe2O3 5.57, FeO 29.39, MnO 1.27, CaO 3.87, MgO 0.52, K2O 0.49, Na2O 0.27, F 0.24, H2O 8.05, O=F -0.10, sum 96.11 wt.%, the amount of H2O was determined from structure refinement, and the valence state of Fe was calculated from structure refinement in accord with Mossbauer spectroscopy. The empirical formula, calculated on the basis of eight (Si + Al) p.f.u., is (Ca0.95Na0.12K0.14)Σ1.21(Fe2+5.65Fe3+0.93Mn0.25Mg0.18)Σ7.01(Ti1.86Nb0.06Zr0.05Fe3+)Σ2 (Si7091Al0.09)Σ8O34.61H12.34F0.17, Z = 1. The infrared spectrum of the mineral contains the following absorption frequencies: 3588, ∽3398 (broad), ∽3204 (broad), 1628, 1069, 1009, 942, 702, 655 and 560 cm–1. The crystal structure of the mineral was solved by direct methods and refined to an R1 index of 21.81%. The main structural unit in the sveinbergeite structure is an HOH layer which is topologically identical to that in the astrophyllite structure. Sveinbergeite differs from all other minerals of the astrophyllite group in the composition and topology of the interstitial A and B sites and linkage of adjacent HOH layers. The mineral is named in honour of Svein Arne Berge (b. 1949), a noted Norwegian amateur mineralogist and collector who was the first to observe and record this mineral from its type locality as a potential new species.

Ianbruceite, ideally [Zn2(OH)(H2O)(AsO4)](H2O)2, a new arsenate mineral from the Tsumeb mine, Otjikoto (Oshikoto) region, Namibia: description and crystal structure

2012 ◽  
Vol 76 (5) ◽  
pp. 1119-1131 ◽  
Author(s):  
M. A. Cooper ◽  
Y. A. Abdu ◽  
N. A. Ball ◽  
F. C. Hawthorne ◽  
M. E. Back ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Chemical Analysis ◽  
Electron Microprobe ◽  
Lone Pair ◽  
Direct Methods ◽  
Crystal Structure Analysis ◽  
Monoclinic Space Group ◽  
Calculated Density ◽  
Perfect Cleavage ◽  
Mohs Hardness

AbstractIanbruceite, ideally [Zn2(OH)(H2O)(AsO4)](H2O)2, is a new supergene mineral from the Tsumeb mine, Otjikoto (Oshikoto) region, Namibia. It occurs as thin platy crystals up to 80 μm long and a few μm thick, which form flattened aggregates up to 0.10 mm across, and ellipsoidal aggregates up to 0.5 mm across. It is associated with coarse white leiteite, dark blue köttigite, minor legrandite and adamite. Ianbruceite is sky blue to very pale blue with a white streak and a vitreous lustre; it does not fluoresce under ultraviolet light. It has perfect cleavage parallel to (100), is flexible, and deforms plastically. The Mohs hardness is 1 and the calculated density is 3.197 g cm-3. The refractive indices are α = 1.601, β = 1.660, γ = 1.662, all ±0.002; 2Vobs = 18(2)°, 2Vcalc = 20°, and the dispersion is r < v, weak. Ianbruceite is monoclinic, space group P21/c, a = 11.793(2), b = 9.1138(14), c = 6.8265(10) Å, β = 103.859(9)°, V = 712.3(3) Å3, Z = 4, a:b:c = 1.2940:1:0.7490. The seven strongest lines in the X-ray powder diffraction pattern [d(Å), I, (hkl)] are as follows: 11.29, 100, (100); 2.922, 17, (130); 3.143, 15, (202); 3.744, 11, (300); 2.655, 9, (230); 1.598, 8, (152); 2.252, 7, (222). Chemical analysis by electron microprobe gave As2O5 36.27, As2O3 1.26, Al2O3 0.37, ZnO 49.72, MnO 0.32, FeO 0.71, K2O 0.25, H2Ocalc 19.89, sum 108.79 wt.%; the very high oxide sum is due to the fact that the calculated H2O content is determined from crystal-structure analysis, but H2O is lost under vacuum in the electron microprobe.The crystal structure of ianbruceite was solved by direct methods and refined to an R1 index of 8.6%. The As is tetrahedrally coordinated by four O anions with a mean As O distance of 1.687 Å. Zigzag [[5]Zn[6]Znϕ7] chains extend in the c direction and are linked in the b direction by sharing corners with (AsO4) tetrahedra to form slabs with a composition [Zn2(OH)(H2O)(AsO4)]. The space between these slabs is filled with disordered (H2O) groups and minor lone-pair stereoactive As3+. The ideal formula derived from chemical analysis and crystal-structure solution and refinement is [Zn2(OH)(H2O)(AsO4)](H2O)2.

Description and crystal structure of domerockite, Cu4(AsO4)(AsO3OH)(OH)3·H2O, a new mineral from the Dome Rock Mine, South Australia

2013 ◽  
Vol 77 (4) ◽  
pp. 509-522 ◽  
Author(s):  
P. Elliott ◽  
U. Kolitsch ◽  
A. C. Willis ◽  
E. Libowitzky
Keyword(s):  
Crystal Structure ◽  
Structure Refinement ◽  
South Australia ◽  
Direct Methods ◽  
New Mineral ◽  
Calculated Density ◽  
Bluish Green ◽  
Distorted Octahedra ◽  
Mohs Hardness ◽  
Greenish Blue

AbstractDomerockite, Cu4(AsO4)2(AsO3OH)(OH)3·H2O, is a new mineral from the Dome Rock Mine, South Australia. It occurs as aggregates of bluish green, equant to short prismatic and tabular crystals up to 0.3 mm long and 0.2 mm across. Domerockite is translucent, with a vitreous lustre and pale green streak. It displays no fluorescence under UV irradiation. The mineral is brittle with an uneven fracture, a Mohs hardness of ∼3 and a calculated density of 4.44 g/cm3 (based on the structure refinement). Optically, it is biaxial negative, with α = 1.798(4), β = 1.814(4), γ = 1.817(4), 2Vcalc. = 46°; pleochroism is very weak; X pale greenish yellow, Y greenish blue, Z greenish blue; absorption X < Y = Z; orientation is uncertain. Chemical analysis by electron microprobe gave CuO 52.04, ZnO 0.78, BaO 0.11, As2O537.67, P2O50.32, SiO20.24, H2O 8.84, total 100.00 wt.%, with H2O calculated by difference. The empirical chemical formula is (Cu3.94, Zn0.06)Σ4.00H0.91(As1.97, P0.03, Si0.02)Σ2.02O8(OH)3.00˙H2O based on 12 oxygen atoms.Domerockite is triclinic, space group P, with a = 5.378(11), b = 8.962(18) c = 9.841(2) Å, α = 75.25(3), β = 83.56(3), γ = 79.97(3)°, V = 450.5(16) Å3 and Z = 2. The eight strongest lines in the X-ray powder diffraction pattern are [d (Å), (I)(hkl)]: 4.716 (30)(101, 002, 111), 3.697 (25)(121), 3.605 (30)(120, 12), 3.119 (60)(12), 3.073 (100)(1), 2.856 (40)(02, 030), 2.464 (50)(212, 13), 2.443 (40)(014). The crystal structure of domerockite has been solved by direct methods and refined to an R index of 7.44% using 2635 observed reflections. The structure comprises [Cuφ4] (φ = O, OH) chains of edge-sharing sharing, distorted octahedra that extend along [10] and are decorated by AsO4 tetrahedra to form sheets in the (010) plane. Dimers of edge-sharing [CuO4(OH)(H2O)] octahedra share corners with dimers of edge-sharing [CuO4(OH)] square pyramids to form zigzag chains which extend along [101]. The chains lie between and link to the sheets by sharings corners of octahedra, square pyramids and tetrahedra to form a heteropolyhedral framework.

Wiklundite, ideally Pb2[4](Mn2+,Zn)3(Fe3+,Mn2+)2(Mn2+,Mg)19(As3+O3)2[(Si,As5+)O4]6(OH)18Cl6, a new mineral from Långban, Filipstad, Värmland, Sweden: Description and crystal structure

2017 ◽  
Vol 81 (4) ◽  
pp. 841-855 ◽  
Author(s):  
Mark A. Cooper ◽  
Frank C. Hawthorne ◽  
Jörgen Langhof ◽  
Ulf Hålenius ◽  
Dan Holtstam
Keyword(s):  
Crystal Structure ◽  
Structure Refinement ◽  
Direct Methods ◽  
New Mineral ◽  
Silicate Mineral ◽  
Calculated Density ◽  
International Mineralogical Association ◽  
Perfect Cleavage

AbstractWiklundite, ideally Pb2[4](Mn2+,Zn)3(Fe3+,Mn2+)2(Mn2+,Mg)19(As3+O3)2[(Si,As5+)O4]6(OH)18Cl6, isa new arseno-silicate mineral from Långban, Filipstad, Värmland, Sweden. Both the mineral and the name have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA 2015-057). Wiklundite and a disordered wiklundite-like mineral form radiating, sheaf-like aggregates (up to 1 mm long) of thin brownish-red and slightly bent lath-shaped crystals. It occurs in a dolomite-rich skarn in association with tephroite, mimetite, turneaurite, johnbaumite, jacobsite, barite, native lead, filipstadite andparwelite. Wiklundite is reddish brown to dark brown, and the streak is pale yellowish brown. The lustre is resinous to sub-metallic, almost somewhat bronzy, and wiklundite does not fluoresce under ultraviolet light. The calculated density is 4.072 g cm–3. Wiklundite is brittle with an irregular fracture, and has perfect cleavage on {001}; no parting or twinning was observed. Wiklundite is uniaxial (–), orange red and non-pleochroic in transmitted light, but shows incomplete extinction and distorted interference figures, preventing complete determination of optical properties. Electron-microprobe analysis (H2O calculated from the structure) of wiklundite gave SiO2 11.17, Al2O3 0.06, Fe2O3 4.46, As2O5 0.75, As2O3 6.81, MnO 47.89, ZnO 0.78,CaO 0.09, PbO 14.48, Cl 6.65, H2O 5.18, O=Cl2 –1.50, total 97.11 wt.%, As valences and H2O content taken from the crystal-structure refinement, and Fe3+/(Fe2+ + Fe3+) determined by Mössbauer spectroscopy. Wiklundite is hexagonal-rhombohedral, space group R3c, a = 8.257(2), c = 126.59(4) Å, V = 7474(6) Å3, Z = 6. The crystal structure of wiklundite was solved by direct methods and refined to a final R1 index of 3.2%. The structure consists of a stacking of five layers of polyhedra: three layers consist of trimers of edge-sharing Mn2+-dominant octahedra linked by (SiO4) tetrahedra, (Fe3+(OH)6) dominant octahedra and (AsO3) triangular pyramids; one layerof corner-sharing (SiO4) and (Mn2+O4) tetrahedra; and one layer of (Mn2+Cl6) octahedra and (Pb2+(OH)3Cl6) polyhedra. The mineral is named after Markus Wiklund (b. 1969) and Stefan Wiklund (b. 1972), the well-known Swedish mineral collectors who jointly found the specimen containing the mineral.

Fluoro-sodic-ferropedrizite, NaLi2(Fe22+Al2Li)Si8O22F2, a new mineral of the amphibole group from the Sutlug River, Tuva Republic, Russia: description and crystal structure

2009 ◽  
Vol 73 (3) ◽  
pp. 487-494 ◽  
Author(s):  
R. Oberti ◽  
M. Boiocchi ◽  
N. A. Ball ◽  
F. C. Hawthorne
Keyword(s):  
Crystal Structure ◽  
Country Rock ◽  
Structure Refinement ◽  
Polarized Light ◽  
New Mineral ◽  
Monoclinic Space Group ◽  
Crystal Structure Refinement ◽  
Calculated Density ◽  
Plagioclase Feldspar ◽  
Mohs Hardness

AbstractFluoro-sodic-ferropedrizite, ideally ANaBLi2C()TSi8O22WF2, is a new mineral of the amphibole group from the Sutlug River, Tuva Republic, Russia. It occurs at the endogenic contact of a Li-pegmatite with country rocks near to a diabase dyke and formed by reaction of the pegmatitic melt with the country rock. Fluoro-sodic-ferropedrizite occurs as prismatic to acicular crystals, ranging in length from 0.1–3 cm and widths of up to 50 μm. Crystals occur inparallel to sub-parallel aggregates up to 5 mm across ina matrix of calcite and plagioclase feldspar. Crystals are pale bluish-grey with a greyish-white streak.Fluoro-sodic-ferropedrizite is brittle, has a Mohs hardness of ~6 and a splintery fracture; it is non-fluorescent with perfect {110} cleavage, no observable parting, and has a calculated density of 3.116 g cm–3. In plane-polarized light, it is pleochroic, X = pale purple-grey, Y = light grey, Z = colourless; X ^ a = 71.2º (in β acute), Y || b, Z ^ c = 83.4º (in β obtuse). Fluoro-sodic-ferropedrizite is biaxial positive, α = 1.642(1), β = 1.644(1), γ = 1.652(1); 2V(obs) = 68.0(3)º, 2V(calc) = 56.4º. Fluoro-sodic-ferropedrizite is monoclinic, space group C2/m, a = 9.3720(4) Å, b = 17.6312(8) Å, c = 5.2732(3) Å, β = 102.247(4)º, V = 851.5(2) Å3, Z = 2. The strongest ten X-ray diffraction lines in the powder patternare (d in Å ,(I),(hkl)): 8.146,(10),(110); 2.686,(9),(151); 3.008,(8),(310); 4.430,(7),(021); 2.485,(6),(02); 3.383,(4),(131); 2.876,(3),(51, 11); 2.199,(3),(12); 4.030,(2),(111) and 3.795,(2),(31). Analysis by a combination of electron microprobe and crystal-structure refinement gives SiO2 59.81, Al2O3 12.66, TiO2 0.09, FeO 10.32, MgO 5.56, MnO 0.73, ZnO 0.17, CaO 0.20, Na2O 2.81, Li2O 4.80, F 2.43, H2Ocalc 1.10, sum = 99.65 wt.%. The formula unit, calculated on the basis of 24(O,OH,F) is A(Na0.68)B(Li1.92Na0.05Ca0.03)C() T(Si7.98Al0.02)O22W(F1.03OH0.97). Crystal-structure refinement shows Li to be completely ordered at the M(3) and M(4) sites. Fluoro-sodic-ferropedrizite, ideally ANaBLi2C()TSi8O22WF2, is related to the theoretical end-member ‘sodic-pedrizite’, ANaBLi2C(Mg2Al2Li)TSi8O22W(OH)2, by the substitutions CFe2+ → CMg and WF → W(OH).

Odigitriaite, CsNa5Ca5[Si14B2O38]F2, a new caesium borosilicate mineral from the Darai-Pioz alkaline massif, Tajikistan: Description and crystal structure

2017 ◽  
Vol 81 (1) ◽  
pp. 113-122 ◽  
Author(s):  
Atali A. Agakhanov ◽  
Leonid A. Pautov ◽  
Elena Sokolova ◽  
Frank C. Hawthorne ◽  
Vladimir Yu Karpenko ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Double Layer ◽  
Direct Methods ◽  
Double Layers ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
Calculated Density ◽  
X Ray ◽  
Mohs Hardness ◽  
Alkaline Massif

AbstractOdigitriaite, a new Cs, Na, Ca borosilicate mineral, was discovered in moraine adjacent to the Darai-Pioz alkaline massif in the upper reaches of the Darai-Pioz river at the intersection of the Turkestansky, Zeravshansky and Alaisky mountain ridges, Tajikistan. It occurs as irregular thin flakes associated with quartz, pectolite, baratovite, fluorite, pekovite, polylithionite, aegirine, leucosphenite, pyrochlore, neptunite, reedmergnerite, mendeleevite-(Ce), zeravshanite and sokolovaite. It is colourless with a white streak, is translucent and has a vitreous lustre; it does not fluoresce under ultraviolet light. Odigitriaite is brittle with an uneven fracture and a Mohs hardness of 5. The calculated density is 2.80(2) g/cm3. The indices of refraction are α = 1.502, β = 1.564, γ = 1.576; 2Vobs = 46(2)°, dispersion is weak r > v, and there is no pleochroism. The chemical composition is as follows (electron microprobe, H2O calculated from structure): SiO2 55.30, Al2O3 0.09, Y2O3 0.44, MnO 0.94, FeO 0.10, PbO 0.21, K2O 0.01 Cs2O 8.36, B2O3 4.75, H2O 0.37, F 1.74, O = F2 –0.74, total 99.43 wt.%. The empirical formula of odigitriaite is Cs0.90Na5.12Ca4.68Mn0.20Y0.06Fe0.02Pb0.01[Si13.92Al0.03B2.06O38]F1.39(OH)0.62. The end-member formula is CsNa5Ca5[Si14B2O38]F2. The strong reflections in the powder X-ray diffraction pattern are: [(d, Å), (I, %), (hkl)]: 5.45 (25) (1 1 3), 4.66 (33) (3 1 1), 4.40 (26) (0 2 2), 4.10 (36) (3 1 3), 3.95 (25) (3̄ 1 3), 2.85 (31) (2 2 2), 2.68 (40) (0 0 6), 3.62 (45) (0 2 4), 3.35 (100) (2̄ 2 4), 3.31 (30) (3̄ 1 5), 3.25 (35) (4 0 4), 3.04 (60) (4̄ 2 2), 2.925 (22) (4̄ 2 3), 1.813 (23) (9 1 0). Odigitriaite is monoclinic, space group C2/c, a = 16.652(5), b = 9.598 (3), c = 22.120(7) Å, β= 92.875(14)°, V = 3530.9(1.9) Å3, Z = 4. The crystal structure of odigitriaite was solved by direct methods and refined to an R1 value of 2.75% based on single-crystal X-ray data. It is a double-layer sheet-borosilicate mineral; Cs and Na are intercalated within the double-layer sheet, and the double layers are linked by interstitial Ca and Na atoms.

Hydroniumpharmacosiderite, a new member of the pharmacosiderite supergroup from Cornwall, UK: structure and description

2010 ◽  
Vol 74 (5) ◽  
pp. 863-869 ◽  
Author(s):  
S. J. Mills ◽  
A. R. Kampf ◽  
P. A. Williams ◽  
P. Leverett ◽  
G. Poirier ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Diffraction Pattern ◽  
Powder Diffraction ◽  
Empirical Formula ◽  
Direct Methods ◽  
Structure Type ◽  
New Mineral ◽  
Calculated Density ◽  
X Ray ◽  
Mohs Hardness

AbstractHydroniumpharmacosiderite, ideally (H3O)Fe4(AsO4)3(OH)4·4H2O, is a new mineral from Cornwall, UK, probably from the St. Day group of mines. It occurs as a single yellowish green, slightly elongated cube, measuring 0.17 mm ×0.14 mm ×0.14 mm. The mineral is transparent with a vitreous lustre. It is brittle with a cleavage on {001}, has an irregular fracture, a white streak and a Mohs hardness of 2–3 (determined on H3O-exchanged pharmacosiderite). Hydroniumpharmacosiderite has a calculated density of 2.559 g cm–3 for the empirical formula. The empirical formula, based upon 20.5 oxygen atoms, is: [(H3O)0.50K0.48Na0.06]1.04(Fe3.79Al0.22)4.01[(As2.73P0.15)2.88O12](OH)4·4H2.14O. The five strongest lines in the X-ray powder diffraction pattern are [dobs(Å),Iobs,(hkl)]: 8.050,100,(001); 3.265,35,(112); 2.412,30,(113); 2.830,23,(202); 4.628,22,(111). Hydroniumpharmacosiderite is cubic, space group with a = 7.9587(2) Å, V = 504.11(2) Å3 and Z = 1. The crystal structure was solved by direct methods and refined to R1 = 0.0481 for 520 reflections with I > 2σ(I). The structure is consistent with determinations for H3O-exhchanged pharmacosiderite and the general pharmacosiderite structure type.

scholarly journals Luxembourgite, AgCuPbBi<sub>4</sub>Se<sub>8</sub>, a new mineral species from Bivels, Grand Duchy of Luxembourg

2020 ◽  
Vol 32 (4) ◽  
pp. 449-455
Author(s):  
Simon Philippo ◽  
Frédéric Hatert ◽  
Yannick Bruni ◽  
Pietro Vignola ◽  
Jiří Sejkora
Keyword(s):  
Crystal Structure ◽  
Structure Refinement ◽  
New Mineral ◽  
Tetrahedral Position ◽  
Calculated Density ◽  
Octahedral Sites ◽  
New Mineral Species ◽  
Distorted Octahedral ◽  
Mohs Hardness ◽  
Grand Duchy

Abstract. Luxembourgite, ideally AgCuPbBi4Se8, is a new selenide discovered at Bivels, Grand Duchy of Luxembourg. The mineral forms tiny fibres reaching 200 µm in length and 5 µm in diameter, which are deposited on dolomite crystals. Luxembourgite is grey, with a metallic lustre and without cleavage planes; its Mohs hardness is 3 and its calculated density is 8.00 g cm−3. Electron-microprobe analyses indicate an empirical formula Ag1.00(Cu0.82Ag0.20Fe0.01)Σ1.03Pb1.13Bi4.11(Se7.72S0.01)Σ7.73, calculated on the basis of 15 atoms per formula unit. A single-crystal structure refinement was performed to R1=0.0476, in the P21∕m space group, with a=13.002(1), b=4.1543(3), c=15.312(2) Å, β=108.92(1)∘, V=782.4(2) Å3, Z=2. The crystal structure is similar to that of litochlebite and watkinsonite and can be described as an alternation of two types of anionic layers: a pseudotetragonal layer four atoms thick and a pseudohexagonal layer that is one atom thick. In the pseudotetragonal layers the Bi1, Bi2 ,Bi3, Pb, and Ag1 atoms are localised, while the Cu2 and Bi4 atoms occur between the pseudotetragonal and the pseudohexagonal layers. Bi1, Bi2, and Bi3 atoms occur in weakly distorted octahedral sites, whereas Bi4 occurs in a distorted 7-coordinated site. Ag1 occupies a fairly regular octahedral site, Cu2 a tetrahedral position, and Pb occurs on a very distorted 8-coordinated site.

Siwaqaite, Ca6Al2(CrO4)3(OH)12·26H2O, a new mineral of the ettringite group from the pyrometamorphic Daba-Siwaqa complex, Jordan

2020 ◽  
Vol 105 (3) ◽  
pp. 409-421 ◽  
Author(s):  
Rafał Juroszek ◽  
Biljana Krüger ◽  
Irina Galuskina ◽  
Hannes Krüger ◽  
Yevgeny Vapnik ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Direct Methods ◽  
New Mineral ◽  
Calculated Density ◽  
Oh Groups ◽  
The North ◽  
Yellow Color ◽  
Raman And Infrared Spectroscopy ◽  
Ettringite Group ◽  
Perfect Cleavage

Abstract A new mineral, siwaqaite, ideally Ca6Al2(CrO4)3(OH)12·26H2O [P31c, Z = 2, a = 11.3640(2) Å, c = 21.4485(2) Å, V = 2398.78(9) Å3], a member of the ettringite group, was discovered in thin veins and small cavities within the spurrite marble at the North Siwaqa complex, Lisdan-Siwaqa Fault, Hashem region, Jordan. This complex belongs to the widespread pyrometamorphic rock of the Hatrurim Complex. The spurrite marble is mainly composed of calcite, fluorapatite, and brownmillerite. Siwaqaite occurs with calcite and minerals of the baryte-hashemite series. It forms hexagonal prismatic crystals up to 250 μm in size, but most common are grain aggregates. Siwaqaite exhibits a canary yellow color and a yellowish-gray streak. The mineral is transparent and has a vitreous luster. It shows perfect cleavage on (1010). Parting or twinning is not observed. The calculated density of siwaqaite is 1.819 g/cm3. Siwaqaite is optically uniaxial (–) with ω = 1.512(2), ε = 1.502(2) (589 nm), and non-pleochroic. The empirical formula of the holotype siwaqaite calculated on the basis of 8 framework cations and 26 water molecules is Ca6.01(Al1.87Si0.12)Σ1.99[(CrO4)1.71(SO4)1.13(SeO4)0.40]Σ3.24(OH)11.63·26H2O. X-ray diffraction (XRD), Raman, and infrared spectroscopy confirm the presence of OH- groups and H2O molecules and absence of (CO3)2– groups. The crystal structure of this Cr6+-analog of ettringite was solved by direct methods using single-crystal synchrotron XRD data. The structure was refined to an agreement index R1 = 4.54%. The crystal structure of siwaqaite consists of {Ca6[Al(OH)6]2·24H2O}6+ columns with the inter-column space (channels) occupied by (CrO4)2–, (SO4)2–, (SeO4)2–, and (SO3)2– groups and H2O molecules. The tetrahedrally coordinated site occupied by different anion groups is subjected to disordering and rotation of these tetrahedra within the structure. The temperature of siwaqaite formation is not higher than~70–80 °C, as is evident from the mineral association and as inferred from the formation conditions of the natural and synthetic members of the ettringite group minerals, which are stable at conditions of T &lt; 120 °C and pH = 9.5–13. The name siwaqaite is derived from the name of the holotype locality—Siwaqa area, where the mineral was found.

Folvikite, Sb5+Mn3+(Mg,Mn2+)10O8(BO3)4, a new oxyborate mineral from the Kitteln mine, Nordmark ore district, Värmland, Sweden: description and crystal structure

2018 ◽  
Vol 82 (4) ◽  
pp. 821-836
Author(s):  
Mark A. Cooper ◽  
Gunnar Raade ◽  
Neil A. Ball ◽  
Yassir A. Abdu ◽  
Frank C. Hawthorne ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Polarized Light ◽  
Direct Methods ◽  
Refractive Indices ◽  
Monoclinic Space Group ◽  
Calculated Density ◽  
Axial Angle ◽  
Edge Sharing Octahedra ◽  
Mohs Hardness ◽  
Ore District

ABSTRACTFolvikite, Sb5+Mn3+(Mg,Mn2+)10O8(BO3)4, is a new oxyborate mineral from the Kitteln mine, Värmland, Sweden, where it occurs as a primary skarn mineral embedded in calcite. It forms striated prismatic crystals up to 0.3 mm, and is black to dark reddish-brown with submetallic lustre and a reddish-brown streak. It is brittle, has a Mohs hardness of 6, and the calculated density is 4.14 g/cm3. Folvikite is biaxial with indeterminate optic sign due to pervasive twinning. The optic axial angle is 68.9(4)°. Refractive indices were not measured; the calculated mean refractive index is 1.85. Strong pleochroism was observed in plane-polarized light: AB = brown (intermediate), OB = dark brown (maximum) and ON = honey brown (minimum). Folvikite is monoclinic, space group P2, a = 5.3767(10), b = 6.2108(10), c = 10.9389(18) Å, β = 94.399(9)°, V = 364.22(16) Å3 and Z = 1. Chemical analysis by electron microprobe gave Sb2O5 18.15, MgO 24.11, MnO 29.73, Mn2O3 11.62, Al2O3 0.27, Fe2O3 0.45, B2O3 15.27, sum 99.60 wt.%. The B2O3 content was assigned as B = 4 apfu and the Mn2O3 / (MnO + Mn2O3) ratio was determined from the crystal structure. The empirical formula was normalized on the basis of 20 anions pfu: (Sb5+1.02Mn3+1.34Al0.05Fe3+0.05Mg5.46Mn2+3.82□0.26)Σ12O8(BO3)4. A simplified formula may be written as Sb5+Mn3+(Mg,Mn2+)10O8(BO3)4 with Z = 1. The crystal structure was solved by direct methods and refined to an R1 index of 4.1%. Folvikite is a member of the (3 Å) zigzag wallpaper-borate structures in which chains of edge-sharing octahedra extend along the c axis and are cross-linked by BO3 groups. There are five X sites partly occupied by Mn2+ > Mg, one octahedrally coordinated M-site occupied by Sb5+ > Mg, two M sites occupied by Mg ≥ Mn > Sb5+, two M sites occupied by Mn3+ > Mn2+, two M sites occupied by Mg > Mn2+, and one M-site occupied by Mg > □; plus two [3]-coordinated B sites occupied by B. As with the other zigzag borates, the polyhedra are arranged in F-walls, C-walls and S-columns.

Beusite-(Ca), ideally CaMn22+(PO4)2, a new graftonite-group mineral from the Yellowknife pegmatite field, Northwest Territories, Canada: Description and crystal structure

2018 ◽  
Vol 82 (6) ◽  
pp. 1323-1332 ◽  
Author(s):  
Frank C. Hawthorne ◽  
Michael A. Wise ◽  
Petr Černý ◽  
Yassir A. Abdu ◽  
Neil A. Ball ◽  
...  
Keyword(s):  
Crystal Structure ◽  
High Temperature ◽  
Northwest Territories ◽  
Parent Phase ◽  
Polarized Light ◽  
Rare Element ◽  
Calculated Density ◽  
Group Mineral ◽  
Axial Angle ◽  
Mohs Hardness

ABSTRACTBeusite-(Ca), ideally Ca${\rm Mn}_{\rm 2}^{2 +} $(PO4)2, is a new graftonite-group mineral from the Yellowknife pegmatite field, Northwest Territories, Canada. It occurs in a beryl–columbite–phosphate rare-element pegmatite where it is commonly intergrown with triphylite–lithiophilite or sarcopside, and may form by exsolution from a high-temperature (Li,Ca)-rich graftonite-like parent phase. It occurs as pale-brown lamellae 0.1–1.5 mm wide in triphylite, and is pale brown with a vitreous lustre and a very pale-brown streak. It is brittle, has a Mohs hardness of 5, and the calculated density is 3.610 g/cm3. Beusite-(Ca) is colourless in plane-polarized light, and is biaxial (+) with α = 1.685(2), β = 1.688(2), γ = 1.700(5), and the optic axial angle is 46.0(5)°. It is non-pleochroic with X || b; Y ˄ a = 40.3° in β obtuse; Z ˄ a = 49.7° in β acute. Beusite-(Ca) is monoclinic, has space group P21/c, a = 8.799(2), b = 11.724(2), c = 6.170(1) Å, β = 99.23(3)°, V = 628.3(1) Å3 and Z = 4. Chemical analysis by electron microprobe gave P2O5 41.63, FeO 19.43, MnO 23.63, CaO 15.45, sum 100.14 wt.%. The empirical formula was normalized on the basis of 8 anions pfu: (Ca0.94Fe0.92Mn1.13)Σ2.99(PO4)2.00. The crystal structure was refined to an R1 index of 1.55%. Beusite-(Ca) is a member of the graftonite group with Ca completely ordered at the [8]-coordinated M(1) site.

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