Arsenic-bearing new mineral species from Valletta mine, Maira Valley, Piedmont, Italy: I. Grandaite, Sr2Al(AsO4)2(OH), description and crystal structure

2014 ◽  
Vol 78 (3) ◽  
pp. 757-774 ◽  
Author(s):  
F. Cámara ◽  
M. E. Ciriotti ◽  
E. Bittarello ◽  
F. Nestola ◽  
F. Massimi ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Divalent Cations ◽  
Crystal Structure Analysis ◽  
Mineral Species ◽  
New Mineral ◽  
Monoclinic Space Group ◽  
Calculated Density ◽  
Oh Groups ◽  
International Mineralogical Association ◽  
New Mineral Species

AbstractThe new mineral species grandaite, ideally Sr2Al(AsO4)2(OH), has been discovered on the dump of Valletta mine, Maira Valley, Cuneo province, Piedmont, Italy. Its origin is related to the reaction between the ore minerals and hydrothermal solutions. It occurs in thin masses of bright orange to salmon to brown coloured crystals, or infrequently as fan-like aggregates of small (<1 mm) crystals, with reddish-brown streak and waxy to vitreous lustre. Grandaite is associated with aegirine, baryte, braunite, hematite, tilasite, quartz, unidentified Mn oxides and Mn silicates under study.Grandaite is biaxial (+) with refractive indices α = 1.726(1), β = 1.731(1), γ = 1.752(1). Its calculated density is 4.378 g/cm3. Grandaite is monoclinic, space groupP21/m, witha= 7.5764(5),b= 5.9507(4),c= 8.8050(6) Å, β = 112.551(2)°,V= 366.62(4) Å3andZ= 2. The eight strongest diffraction lines of the observed X-ray powder diffraction pattern are [din Å, (I), (hkl)]: 3.194 (100)(11), 2.981 (50.9)(020), 2.922 (40.2)(03), 2.743 (31.4)(120), 2.705 (65.2)(112), 2.087 (51.8) (23), 1.685 (24.5)(321), 1.663 (27.7)(132). Chemical analyses by electron microprobe gave (wt.%) SrO 29.81, CaO 7.28, BaO 1.56, Al2O37.07, Fe2O32.34, Mn2O31.88, MgO 1.04, PbO 0.43, As2O544.95, V2O50.50, P2O50.09, sum 96.95; H2O 1.83 wt.% was calculated by stoichiometry from the results of the crystal-structure analysis. Raman and infrared spectroscopies confirmed the presence of (AsO4)3−and OH groups. The empirical formula calculated on the basis of 9 O a.p.f.u., in agreement with the structural results, is (Sr1.41Ca0.64Ba0.05Pb0.01)∑=2.11(Al0.68Fe0.143+Mn0.123+Mg0.13)∑=1.07[(As0.96V0.01)∑=0.97O4]2(OH), the simplified formula is (Sr,Ca)2(Al,Fe3+)(AsO4)2(OH) and the ideal formula is Sr2Al(AsO4)2(OH).The crystal structure was solved by direct methods and found to be topologically identical to that of arsenbrackebuschite. The structure model was refined on the basis of 1442 observed reflections toR1= 2.78%. In the structure of grandaite, chains of edge-sharingM3+octahedra run along [010] and share vertices with T5+tetrahedra, building up [M3+(T5+O4)2(OH, H2O)] units, which are connected through interstitial divalent cations. Grandaite is named after the informal appellation of the province where the type locality is located. The new mineral was approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification (IMA2013-059). The discovery of grandaite and of other members of the group (description still in progress) opens up the possibility of exploring the crystal chemistry of the brackebuschite supergroup.

Schlüterite-(Y), ideally (Y,REE)2Al(Si2O7)(OH)2F, a new mineral species from the Stetind pegmatite, Tysfjord, Nordland, Norway: description and crystal structure

2013 ◽  
Vol 77 (3) ◽  
pp. 353-366 ◽  
Author(s):  
M. A. Cooper ◽  
T. A. Husdal ◽  
N. A. Ball ◽  
Y. A. Abdu ◽  
F. C. Hawthorne
Keyword(s):  
Crystal Structure ◽  
Direct Methods ◽  
Crystal Structure Analysis ◽  
Mineral Species ◽  
New Mineral ◽  
Monoclinic Space Group ◽  
Silicate Mineral ◽  
Dominant Form ◽  
Calculated Density ◽  
New Mineral Species

AbstractSchlüterite-(Y), ideally (Y,REE)2Al(Si2O7)(OH)2F, is a new silicate mineral species from the Stetind pegmatite, Tysfjord, Nordland, Norway. It forms dense, fibrous, radiating aggregates (up to ∼2 mm) diverging to individual needle-like crystals (up to ∼1 mm long) in cavities. Crystals are acicular to bladed, flattened on {001} and elongated along [010], and the dominant form is {001}. Schlüterite-(Y) is transparent, pale pink with a white streak and a vitreous lustre, and does not fluoresce under short-wave ultraviolet light. Mohs hardness is 5½–6, and schlüterite-(Y) is brittle with an irregular fracture, and has no cleavage. The calculated density is 4.644 g/cm3. The indices of refraction are α = 1.755, β = 1.760, γ = 1.770, all ± 0.005, 2Vobs = 71.8 (5)°, 2Vcalc = 71°, non-pleochroic, optic orientation is X ˆ a = 83.1° (β obtuse), Y//b, Z ˆ c = 50.3° (β acute). Schlüterite-(Y) is monoclinic, space group P21/c, a 7.0722(2), b 5.6198(1), c 21.4390(4) Å, β 122.7756(3)°, V 716.43(5) Å3, Z = 4. The seven strongest lines in the X-ray powder-diffraction pattern are as follows: [d (Å), I, (hkl)]: 4.769, 100, (012); 2.972, 55, (14); 3.289, 51, (112); 2.728, 49, (16); 2.810, 37, (020); 3.013, 37, ((16); 4.507, 36, (004). Chemical analysis by electron microprobe gave SiO2 22.64, Al2O3 9.45, Y2O3 15.35, La2O3 3.25, Ce2O3 9.69, Pr2O3 2.05, Nd2O3 9.50, Sm2O3 3.57, Gd2O3 4.65, Dy2O3 4.21, Er2O3 2.31, Yb2O3 1.86, F 2.71, H2Ocalc 3.78, O = F −1.14, sum 93.88 wt%. The H2O content was determined by crystal-structure analysis. On the basis of 10 anions with (OH) + F = 3 a.p.f.u. (atoms per formula unit), the empirical formula is (Y0.73Ce0.32Nd0.30Gd0.14Dy0.12La0.11Sm0.11Pr0.07Er0.06Yb0.05)Σ=2.01Al0.99Si2.01O7(OH)2.24F0.76. The crystal structure of schlüterite-(Y) was solved by direct methods and refined to an R1 index of 1.8% based on 1422 unique observed reflections. In the structure of schlüterite-(Y), Al(OH)4O2 octahedra share (OH)–(OH) edges to form [MΦ4] chains that are decorated by (Si2O7) groups that bridge O vertices of neighbouring octahedra in a staggered fashion on either side of the chain. These [Al(OH)2(Si2O7)] chains extend parallel to b, and are linked into a continuous framework via bonds to interstitial [8](Y,REE) (= <2.400 Å>) and [9](Y,REE) (= <2.548 Å>) atoms.

scholarly journals As-bearing new mineral species from Valletta mine, Maira Valley, Piedmont, Italy: II. Braccoite, NaMn2+5 [Si5AsO17(OH)](OH), description and crystal structure

2015 ◽  
Vol 79 (1) ◽  
pp. 171-189 ◽  
Author(s):  
Fernando Cámara ◽  
Erica Bittarello ◽  
Marco E. Ciriotti ◽  
Fabrizio Nestola ◽  
Francesco Radica ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Direct Methods ◽  
Mineral Species ◽  
New Mineral ◽  
Wavelength Dispersive Spectroscopy ◽  
Calculated Density ◽  
Oh Groups ◽  
International Mineralogical Association ◽  
Mine Dumps ◽  
New Mineral Species

AbstractThe new mineral species braccoite, ideally NaMn2+5[Si5AsO17(OH)](OH), has been discovered in the Valletta mine dumps, in Maira Valley, Cuneo province, Piedmont, Italy. Its origin is probably related to the reaction between ore minerals and hydrothermal fluids. It occurs as subhedral crystals in brown-red coloured thin masses, with a pale-yellow streak and vitreous to resinous lustre. Braccoite is associated with tiragalloite, for which new data are provided, as well as gamagarite, hematite, manganberzeliite, palenzonaite, quartz, saneroite, tokyoite, unidentified Mn oxides, organic compounds, and Mn arsenates and silicates under study.Braccoite is biaxial positive with refractive indices α = 1.749(1), β = 1.750(1), γ = 1.760(1). It is triclinic, space group P1̄, with a = 9.7354(4), b = 9.9572(3), c = 9.0657(3) Å, α = 92.691(2), β = 117.057(4), γ = 105.323(3)°, V = 740.37(4) Å3 and Z = 2. Its calculated density is 3.56 g/cm3. The ten strongest diffraction lines of the observed powder X-ray diffraction (XRD) pattern are [d in Å, (I), (hkl)]: 3.055 (69)(22̄1), 3.042 (43)(102), 3.012 (65)(32̄1̄), 2.985 (55)(23̄1̄), 2.825 (100)(213̄), 2.708 (92)(220), 2.627 (43)(23̄2̄), 2.381 (58)(41̄1̄), 2.226 (25)(214̄) and 1.680 (433̄)(36). Chemical analyses by wavelength-dispersive spectroscopy electron microprobe gave (wt.%): Na2O 4.06, CaO 0.05, MnO 41.76, MgO 0.96, Al2O3 0.04, CuO 0.02, SiO239.73, As2O5 6.87, V2O5 1.43, SO3 0.01 and F 0.04. H2O 2.20 was calculated on the basis of 2OH groups p.f.u. Raman spectroscopy confirmed the presence of (SiO4)4–, (AsO4)3– and OH groups. The empirical formula, calculated on the basis of Σ cations-(Na,K) = 11 p.f.u., in agreement with the results of the crystal structure, is Na1.06(Mn2+4.46Mn3+0.32Mg0.19V3+0.01Al0.01Ca0.01)[Si5(As0.48Si0.37V5+0.15)O17(OH)](OH0.98F0.02); the simplified formula is Na(Mn,Mg,Al,Ca)5[Si5(As,V,Si)O17(OH)](OH,F).Single-crystal XRD allowed the structure to be solved by direct methods and revealed that braccoite is the As-dominant analogue of saneroite. The structure model was refined on the basis of 4389 observed reflections to R1 = 3.47%. Braccoite is named in honour of Dr Roberto Bracco (b. 1959), a systematic minerals collector with a special interest in manganese minerals. The new mineral was approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification (IMA 2013-093).

Description and crystal structure of bobkingite, a new mineral from New Cliffe Hill Quarry, Stanton-under-Bardon, Leicestershire, UK

2002 ◽  
Vol 66 (2) ◽  
pp. 301-311 ◽  
Author(s):  
F. C. Hawthorne ◽  
M. A. Cooper ◽  
J. D. Grice ◽  
A. C. Roberts ◽  
N. Hubbard
Keyword(s):  
Crystal Structure ◽  
Direct Methods ◽  
Crystal Structure Analysis ◽  
New Mineral ◽  
Monoclinic Space Group ◽  
X Rays ◽  
Calculated Density ◽  
International Mineralogical Association ◽  
Cell Parameters ◽  
Conchoidal Fracture

AbstractBobkingite, ideally is a new mineral from the New Cliffe Hill Quarry, Stantonunder-Bardon, Leicestershire, England. It occurs as very thin (⩽5 µm) transparent plates up to 0.2 mm across, perched on a compact fibrous crust of malachite and crystalline azurite attached to massive cuprite. Crystals are tabular on {001} with dominant {001} and minor {100} and {110}. Bobkingite is a soft pale blue colour with a pale-blue streak, vitreous lustre and no observable fluorescence under ultraviolet light. It has perfect {001} and fair {100} cleavages, no observable parting, conchoidal fracture, and is brittle. Its Mohs' hardness is 3 and the calculated density is 3.254 g/cm3. Bobkingite is biaxial negative with α = 1.724(2), β = 1.745(2), γ = 1.750(2), 2Vγmeas = 33(6)°, 2Vcalc = 52°, pleochroism distinct, X = very pale blue, Z = pale greenish blue, X^a = 22° (in β obtuse), Y = c, Z = b. Bobkingite is monoclinic, space group C2/m, unit-cell parameters (refined from powder data): a = 10.301(8), b = 6.758(3), c = 8.835(7)Å, β = 111.53(6)°, V = 572.1(7)Å3, Z = 2. The seven strongest lines in the X-ray powder-diffraction pattern are [d (Å), I, (hkl)]: 8.199, 100, (001); 5.502, 100, (110); 5.029, 40, (2̄01); 2.883, 80, (310); 2.693, 40, (1̄13); 2.263, 40, (113), (4̄03); 2.188, 50, (2̄23). Chemical analysis by electron microprobe and crystal-structure solution and refinement gave CuO 70.46, Cl 12.71, H2O 19.19, O≡Cl –2.87, sum 99.49 wt.%, where the amount of H2O was determined by crystal-structure analysis. The resulting empirical formula on the basis of 12 anions (including 8 (OH) and 2H2O) is Cu4.99Cl2.02O10H12. The crystal structure was solved by direct methods and refined to an R index of 2.6% for 638 observed reflections measured with X-rays on a single crystal. Three distinct (Cuϕ6) (ϕ = unspecified anion) octahedra share edges to form a framework that is related to the structures of paratacamite and the Cu2(OH)3Cl polymorphs, atacamite and clinoatacamite. The mineral is named for Robert King, formerly of the Department of Geology, Leicester University, prominent mineral collector and founding member of the Russell Society. The mineral and its name have been approved by the Commission on New Minerals and Mineral Names of the International Mineralogical Association.

scholarly journals As-bearing new mineral species from Valletta mine, Maira Valley, Piedmont, Italy: III. Canosioite, Ba2Fe3+(AsO4)2(OH), description and crystal structure

2017 ◽  
Vol 81 (2) ◽  
pp. 305-317 ◽  
Author(s):  
F. Cámara ◽  
E. Bittarello ◽  
M. E. Ciriotti ◽  
F. Nestola ◽  
F. Radica ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Direct Methods ◽  
Mineral Species ◽  
New Mineral ◽  
X Ray Diffraction ◽  
Calculated Density ◽  
International Mineralogical Association ◽  
New Mineral Species ◽  
Ore Minerals ◽  
Mn Oxides

AbstractThe new mineral species canosioite, ideally Ba2Fe3+(AsO4)2(OH), has been discovered in the dump of Valletta mine, Maira Valley, Cuneo Province, Piedmont, Italy. Its origin is probably related to the reaction between ore minerals and hydrothermal fluids. It occurs in reddish-brown granules, subhedral millimetre-size crystals, with a pale yellow streak and vitreous lustre. Canosioite is associated with aegirine, baryte, calcite, hematite, bronze Mn-bearing muscovite, unidentified Mn oxides and unidentified arsenates. Canosioite is biaxial (+) with a 2Vmeas= 84(2)°. It is weakly pleochroic withX= brownish yellow,Y= brown,Z= reddish brown,Z>Y>X. Canosioite is monoclinic,P21/m, witha= 7.8642(4),b= 6.1083(3),c= 9.1670(5) Å, β = 112.874(6)°,V= 405.73(4) Å3andZ= 2. Calculated density is 4.943 g cm–3. The seven strongest diffraction lines of the observed powder X-ray diffraction pattern are [din Å, (I) (hkl)]: 3.713 (18)(111), 3.304 (100)(211̄), 3.058 (31)(020), 3.047 (59)(103̄), 2.801 (73)(112), 2.337 (24)(220), 2.158 (24)(123̄). Electron microprobe analyses gave (wt.%): Na2O 0.06, MgO 0.43, CaO 0.02, NiO 0.02, CuO 0.03, SrO 0.42, BaO 49.36, PbO 1.69, Al2O31.25, Mn2O33.89, Fe2O36.95, Sb2O30.01, SiO20.03, P2O50.02, V2O510.88, As2O524.64, SO3 0.01, F 0.02, H2O1.61 was calculated on the basis of 1 (OH,F,H2O) group per formula unit. Infrared spectroscopy confirmed the presence of OH. The empirical formula calculated on the basis of 9 O apfu, is (Ba1.92Pb0.05Sr0.02Na0.01)∑2.00(Fe0.523+Mn0.293+Al0.15Mg0.06)∑1.02[(As0.64V0.36)∑1.00O4]2[(OH0.92F0.01)(H2O)0.07]and the ideal formula is Ba2Fe3+(AsO4)2(OH). The crystal structure was solved by direct methods and found to be isostructural to that of arsenbrackebuschite. The structure model was refined (R1= 2.6%) on the basis of 1245 observed reflections. Canosioite is named after the small municipality of Canosio, where the type locality, the Valletta mine, is situated. The new mineral and name were approved by the International Mineralogical Association Commission on New Minerals and Mineral Names (IMA2015-030).

scholarly journals Fluoro-aluminoleakeite, NaNa2(Mg2Al2Li)Si8O22F2, a new mineral of the amphibole group from Norra Kärr, Sweden: description and crystal structure

2009 ◽  
Vol 73 (5) ◽  
pp. 817-824 ◽  
Author(s):  
R. Oberti ◽  
F. Cámaraite ◽  
F. C. Hawthorne ◽  
N. A. Ball
Keyword(s):  
Crystal Structure ◽  
Structure Refinement ◽  
Polarized Light ◽  
Crystal Structure Analysis ◽  
New Mineral ◽  
Monoclinic Space Group ◽  
Calculated Density ◽  
Greenish Blue ◽  
Dark Green ◽  
Pale Green

AbstractFluoro-aluminoleakeite, ideally , is a new mineral of the amphibole group from Norra Kärr, Sweden (IMA-CNMMNC 2009-012). It occurs in a proterozoic alkaline intrusion that mainly comprises a fine-grained schistose agpaitic nepheline-syenite (grennaite). Fluoro- aluminoleakeite occurs as isolated prismatic crystals 0.10–2 mm long in a syenitic matrix. Crystals are light greenish-blue with a greenish-blue streak. It 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 3.14 g cm–3. In plane-polarized light, it is pleochroic, X = pale green, Y = dark green, Z = pale green; X ^ a = 62.9° (in β obtuse), Y || b. Fluoro-aluminoleakeite is biaxial negative, α = 1.632(1), β = 1.638(1), γ = 1.643(1); 2Vobs. = 98.0(4)°, 2Vcalc. = 95.5°.MFluoro-aluminoleakeite is monoclinic, space group C2/m, a = 9.7043(5) Å, b = 17.7341(8) Å, c = 5.2833(3) Å, β = 104.067(4)°, V = 882.0(2) Å3, Z = 2. The eight strongest X-ray diffraction lines in the powder-diffraction pattern are [d in Å, (I), (hkl)]: 2.687, (100), (31, 151); 4.435, (80), (021, 040); 3.377, (80), (131); 2.527, (60), (02); 8.342, (50), (110); 3.096, (40), (310); 2.259, (40), (71, 12) and 2.557, (30), (002, 061). Analysis, by a combination of electron microprobe and crystal-structure refinement, gives SiO2 58.61, Al2O3 7.06, TiO2 0.32, FeO 3.27, Fe2O3 6.05, MgO 8.61, MnO 0.73, ZnO 0.43, CaO 0.05, Na2O 9.90, K2O 2.43, Li2O 1.62, F 3.37, H2Ocalc. 0.50, sum 101.08 wt.%. The formula unit, calculated on the basis of 24 (O,OH,F,Cl) p.f.u. with (OH) + F = 2 a.p.f.u., is A(Na0.65 O22W(F1.47OH0.53)Σ=2.00. Crystal-structure analysis shows CLi to be completely ordered at the M(3) site, and provided reliable site populations. Fluoro-aluminoleakeite is related to the end-member leakeite, , by the substitutions CFe3+ → CAl and WF → W(OH).

Description and crystal structure of a new mineral, edwardsite, Cu3Cd2(SO4)2(OH)6·4H2O, from Broken Hill, New South Wales, Australia

2010 ◽  
Vol 74 (1) ◽  
pp. 39-53 ◽  
Author(s):  
P. Elliott ◽  
J. Brugger ◽  
T. Caradoc-Davies
Keyword(s):  
Crystal Structure ◽  
Empirical Formula ◽  
New South ◽  
New South Wales ◽  
Crystal Structure Analysis ◽  
New Mineral ◽  
Monoclinic Space Group ◽  
Calculated Density ◽  
Broken Hill ◽  
South Wales

AbstractEdwardsite, Cu3Cd2(SO4)2(OH)6·4H2O, is a new mineral from the Block 14 Opencut, Broken Hill, New South Wales, Australia. It occurs as druses of tabular and bladed crystals up to 0.06 mm in size, associated with niedermayrite and christelite. Edwardsite is pale blue, transparent with vitreous lustre and has excellent cleavage parallel to {100}. Density was not measured but the calculated density, from the empirical formula, is 3.53 g cm–3 and the Mohs hardness is ∼3. Optically, it is biaxial negative with α ∼ 1.74, β = 1.762(4), γ ∼ 1.77 and 2Vcalc. ∼ +62°. The optical orientation is X = b, Y ∼ a, Z ∼ c. Electron microprobe analysis gave (wt.%): CdO 32.43, CuO 28.06, ZnO 2.26, FeO 0.08, SO3 20.35, H2Ocalc. (from crystal-structure analysis) 14.14, totalling 99.32. The empirical formula, calculated on the basis of 18 oxygen atoms is Cu2.77Cd1.98Zn0.22Fe0.01(SO4)2.00(OH)5.95·4.06H2O. Edwardsite is monoclinic, space group P21/c, with a = 10.863(2) Å, b = 13.129(3) Å, c = 11.169(2) Å, β = 113.04(3)°, V = 1465.9(5) Å3 (single-crystal data) and Z = 4. The eight strongest lines in the powder diffraction pattern are [d (Å), (I/I0), (hkl)]: 9.991, (90), (100); 5.001, (90), (200, 21); 4.591, (45), (20); 3.332, (60), (300, 032); 3.005, (30), (03); 2.824, (40), (2); 2.769, (55), (20, 042, 10); 2.670, (45), (2). The crystal structure was determined by direct methods and refined to R1 = 3.21% using 1904 observed reflections with Fo > 4σ(Fo) collected using synchrotron X-ray radiation (λ = 0.773418 Å). The structure is based on infinite sheets of edge-sharing Cuϕ6 (ϕ: O2–, OH) octahedra and Cdϕ7 (ϕ: O2–, H2O) polyhedra parallel to (100). The sheets are decorated on both sides by corner-sharing (SO4) tetrahedra, which also corner-link to isolated Cdϕ6 octahedra, thus connecting adjacent sheets. Moderate-strong to weak hydrogen bonding provides additional linkage between sheets.

Petewilliamsite, (Ni,Co)30(As2O7)15, a new mineral from Johanngeorgenstadt, Saxony, Germany: description and crystal structure

2004 ◽  
Vol 68 (2) ◽  
pp. 231-240 ◽  
Author(s):  
A. C. Roberts ◽  
P. C. Burns ◽  
R. A. Gault ◽  
A. J. Criddle ◽  
M. N. Feinglos
Keyword(s):  
Crystal Structure ◽  
Electron Microprobe ◽  
Empirical Formula ◽  
Crystal Structure Analysis ◽  
Index Of Refraction ◽  
Maximum Diameter ◽  
New Mineral ◽  
Monoclinic Space Group ◽  
Calculated Density ◽  
Four Square

AbstractPetewilliamsite, ideally (Ni,Co)30(As2O7)15, monoclinic, space group C2, a = 33.256(5), b = 8.482(1), c = 14.191(2) Å, ß = 104.145(3)°, V = 3881.6(11) Å3, a:b:c = 3.9209:1:1.6731, Z = 2, is a new mineral found on a single nickeline-veined quartz specimen from Johanngeorgenstadt, Saxony, Germany. The mineral possesses a pronounced subcell-supercell: a (subcell) = 1/5 a (supercell); b (subcell) = b (supercell); c (subcell) = 1/3 c (supercell), and the strongest six lines of the X-ray powder-diffraction pattern are [d in Å (I) (hkl)]: 4.235(30)(020) ; 3.118(100)(513, 023); 3.005(60); 2.567(50); 1.637(50)(536 ); 1.507(30b)(553, ). It occurs predominantly as scattered patches of mm-sized aggregates which are intimately associated with varicoloured xanthiosite; additional associations include bunsenite, aerugite, rooseveltite, native bismuth, paganoite and two undefined arsenates. Subhedral equant crystals with rounded faces are intimately intergrown in 1 mm-sized aggregates and individual grains do not exceed 0.5 mm in maximum diameter. The average crystal size is variable from 20 μm to 0.3 mm. The colour varies from dark violet-red to dark brownish-red and the streak is pale reddish-brown to pale purplish-brown. Crystals are translucent, brittle, vitreous, and do not fluoresce under ultraviolet light. The mineral shows neither twinning nor cleavage, has an uneven fracture, and the calculated density (for the empirical formula) is 4.904 g/cm3. Electron-microprobe analyses gave NiO 19.45, CoO 18.39, CuO 3.40, CaO 0.17, FeO 0.04, As2O5 60.32, total 101.77 wt.%. The empirical formula, derived from crystal-structure analysis and electron-microprobe analyses, is (Ni14.662+Co13.822+Cu2.412+Ca0.17Fe0.032+)Σ31.09(As1.975+O7)15, based on O = 105 atoms per formula unit (a.p.f.u.). In reflected plane-polarized light in air, petewilliamsite is dark grey with orange to spectral (multicoloured) internal reflections and no obvious bireflectance, anisotropy or pleochroism. Measured reflectance values in air are tabulated; the index of refraction calculated at 589 nm is 1.88. The mineral name honours Professor Peter (‘Pete’) Allan Williams of the University of Western Sydney, New South Wales, Australia, for his contributions to the study of secondary minerals.The crystal structure of petewilliamsite has been solved by direct methods and refined on the basis of F2 using 9212 unique reflections measured with Mo-Kα X-radiation on a diffractometer equipped with a CCDbased detector. The final R1 was 7.68%, calculated for 1273 observed reflections. The structure contains 15 symmetrically distinct As5+ cations, each of which is tetrahedrally coordinated by four O atoms, and pairs of these AsO4 tetrahedra share a vertex which results in As2O7 pyroarsenate groups that are in layers parallel to (010). The structure also has 16 distinct transition-metal M (M: Ni,Co) sites of which there are one tetrahedral, four square bipyramidal, and 11 octahedral arrangements. Adjacent pyroarsenate groups are linked through bonds to M cations. The structure of petewilliamsite is not closely related to other naturally occurring arsenates and it is the first pyroarsenate mineral.

Vapnikite Ca3UO6 – a new double-perovskite mineral from pyrometamorphic larnite rocks of the Jabel Harmun, Palestinian Autonomy, Israel

2014 ◽  
Vol 78 (3) ◽  
pp. 571-581 ◽  
Author(s):  
E. V. Galuskin ◽  
I. O. Galuskina ◽  
J. Kusz ◽  
T. Armbruster ◽  
K. M. Marzec ◽  
...  
Keyword(s):  
Crystal Structure ◽  
High Temperature ◽  
Double Perovskite ◽  
Mineral Species ◽  
New Mineral ◽  
Synthetic Analogue ◽  
Calculated Density ◽  
New Mineral Species ◽  
High Alkalinity ◽  
Small Grains

AbstractThe new mineral species vapnikite, Ca3UO6, was found in larnite pyrometamorphic rocks of the Hatrurim Formation at Jabel Harmun in the Judean desert, Palestinian Autonomy, Israel. Vapnikite is an analogue of the synthetic ordered double-perovskite β-Ca3UO6 and is isostructural with the natural fluorperovskite – cryolite Na3AlF6. Vapnikite Ca3UO6 (P21/n, Z = 2, a = 5.739(1), b = 5.951(1), c = 8.312(1) Å, β = 90.4(1)°, V = 283.9(1) Å3) forms yellow-brown xenomorphic grains with a strong vitreous lustre. Small grains up to 20−30 µm in size are wedged between larnite, brownmillerite and ye’elimite. Vapnikite has irregular fracture, cleavage and parting were not observed. The calculated density is 5.322 g cm−3, the microhardness is VHN25 = 534 kg mm−2 (mean of seven measurements) corresponding to the hardness of ∼5 on the Mohs scale. The crystal structure of vapnikite Ca3UO6 differs from that of its synthetic analogue β-Ca3UO6 by having a larger degree of Ca, U disorder. Vapnikite formed at the high-temperature retrograde stage of pyrometamorphism when larnite rocks were altered by fluids/melts of high alkalinity.

Badakhshanite-(Y), Y2Mn4Al(Si2B7BeO24), a new mineral species of the perettiite group from a granite miarolic pegmatite in Eastern Pamir, the Gorno Badakhshan Autonomous Oblast, Tajikistan

2020 ◽  
Vol 58 (3) ◽  
pp. 381-394
Author(s):  
Leonid A. Pautov ◽  
Mirak A. Mirakov ◽  
Fernando Cámara ◽  
Elena Sokolova ◽  
Frank C. Hawthorne ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Close Association ◽  
Coarse Grained ◽  
New Mineral ◽  
Orthorhombic Space Group ◽  
Calculated Density ◽  
Conchoidal Fracture ◽  
New Mineral Species ◽  
Mohs Hardness ◽  
Cation Sites

ABSTRACT Badakhshanite-(Y), ideally Y2Mn4Al(Si2B7BeO24), is a tetrahedral sheet-structure mineral found in the Dorozhny (Road) miarolitic granitic pegmatite within the Kukurt pegmatite field 45 km E of Murghab, Eastern Pamir, Gorno-Badakhshan Autonomous Oblast, Tajikistan. Badakhshanite-(Y) occurs in medium- to coarse-grained non-graphic albite-microcline-quartz pegmatites in close association with smoky quartz, Sc-bearing spessartine, Sc-bearing tusionite, and schorl. It often grows together with Sc-bearing tusionite and occurs as single columnar crystals ranging from 50 to 400 μm in length, as inclusions in spessartine and tourmaline, and rarely as crystals in blebs along boundaries between garnet, tourmaline, and quartz. Badakhshanite-(Y) is yellow brown and has a white streak and a vitreous luster. It is brittle, with a conchoidal fracture, Mohs hardness of 6.5–7, and calculated density of 4.41 g/cm. In thin section it is transparent and pale yellow, non-pleochroic, biaxial (–), with α = 1.805(2), βcalc = 1.827, γ = 1.835(3) (λ = 590 nm); 2V (meas.) = –60(10)°. Dispersion is weak, r &gt; v. Extinction is straight, elongation is negative. FTIR spectra show the absence of (OH) and H2O groups. Chemical analysis by electron microprobe using WDS (6 points), SIMS, and ICP-OES for B and Be gave SiO2 11.96, ThO2 0.12, Sm2O3 0.17, Gd2O3 0.30, Tb2O3 0.10, Dy2O3 0.73, Ho2O3 0.19, Er2O3 1.34, Tm2O3 0.54, Yb2O3 8.82, Lu2O3 2.32, Y2O3 16.60, Sc2O3 1.57, Al2O3 3.06, B2O3 22.06, FeO 0.94, MnO 23.33, CaO 0.58, BeO 2.84, total 97.57 wt.%.The empirical formula based on 24 O apfu is (Y1.21REE0.78Th0.01)Σ2(Mn3.47Y0.34Ca0.11Fe2+0.08)Σ4(Al0.63Sc0.24Fe2+0.06□0.07)Σ1[(Si2.10B6.69Be1.20)Σ9.99O24], where REE = (Yb0.47Lu0.12Dy0.04Er0.07Tm0.03 Ho0.01Gd0.02Sm0.01Tb0.01)Σ0.78. Badakhshanite-(Y) is orthorhombic, space group Pnma, a 12.852(1), b 4.5848(5), c 12.8539(8) Å, V 757.38(7) Å3, Z = 2. The crystal structure was refined to R1 = 4.31% based on 1431 unique [F &gt; 4σF] reflections. In the crystal structure of badakhshanite-(Y), a layer of tetrahedra parallel to (010) is composed of four different tetrahedrally coordinated sites: Si, B(1), B(2), and T (&lt;Si–O&gt; = 1.623 Å, &lt;B(1)–O&gt; = 1.485 Å, &lt;B(2)–O&gt; = 1.479 Å, &lt;T–O&gt; = 1.557 Å), which form four-, five-, and eight-membered rings, having the composition (Si2B7BeO24). Between the sheets of tetrahedra, there are three cation sites: M(1), M(2), and M(3) (&lt;M(1)–O&gt; = 2.346 Å, &lt;M(2)–O&gt; = 2.356 Å, &lt;M(3)–O&gt; = 2.016 Å) occupied by Y(REE), Mn2+(Y, Ca, Fe2+), and Al(Sc), respectively. The M(1,2) sites ideally give Y2Mn4apfu; the M(3) site ideally gives Al apfu. Badakhshanite-(Y) is an Al- and Be-analogue of perettiite-(Y).

scholarly journals Langhofite, Pb2(OH)[WO4(OH)], a new mineral from Långban, Sweden

2020 ◽  
Vol 84 (3) ◽  
pp. 381-389
Author(s):  
Dan Holtstam ◽  
Fernando Cámara ◽  
Andreas Karlsson
Keyword(s):  
New Mineral ◽  
Calculated Density ◽  
Triclinic Space Group ◽  
Oh Groups ◽  
International Mineralogical Association ◽  
Cell Parameters ◽  
Discovery Sample ◽  
Vibration Spectroscopy ◽  
Perfect Cleavage ◽  
Mohs Hardness

AbstractLanghofite, ideally Pb2(OH)[WO4(OH)], is a new mineral from the Långban mine, Värmland, Sweden. The mineral and its name were approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification (IMA2019-005). It occurs in a small vug in hematite–pyroxene skarn associated with calcite, baryte, fluorapatite, mimetite and minor sulfide minerals. Langhofite is triclinic, space group P$\bar{1}$, and unit-cell parameters a = 6.6154(1) Å, b = 7.0766(1) Å, c = 7.3296(1) Å, α = 118.175(2)°, β = 94.451(1)°, γ = 101.146(1)° and V = 291.06(1) Å3 for Z = 2. The seven strongest Bragg peaks from powder X-ray diffractometry are [dobs, Å (I)(hkl)]: 6.04(24)(010), 3.26(22)(11$\bar{2}$), 3.181(19)(200), 3.079(24)(1$\bar{1}$2), 3.016(100)(020), 2.054(20)(3$\bar{1}$1) and 2.050(18)(13$\bar{2}$). Langhofite occurs as euhedral crystals up to 4 mm, elongated along the a axis, with lengthwise striation. Mohs hardness is ca. 2½, based on VHN25 data obtained in the range 130–192. The mineral is brittle, with perfect {010} and {100} cleavages. The calculated density based on the ideal formula is 7.95(1) g⋅cm–3. Langhofite is colourless to white (non-pleochroic) and transparent, with a white streak and adamantine lustre. Reflectance curves show normal dispersion, with maximum values 15.7–13.4% within 400–700 nm. Electron microprobe analyses yield only the metals Pb and W above the detection level. The presence of OH-groups is demonstrated with vibration spectroscopy, from band maxima present at ~3470 and 3330 cm–1. A distinct Raman peak at ca. 862 cm–1 is related to symmetric W–oxygen stretching vibrations. The crystal structure is novel and was refined to R = 1.6%. It contains [W2O8(OH)2]6– edge-sharing dimers (with highly distorted WO6-octahedra) forming chains along [101] with [(OH)2Pb4]6+ dimers formed by (OH)Pb3 triangles. Chains configure (010) layers linked along [010] by long and weak Pb–O bonds, thus explaining the observed perfect cleavage on {010}. The mineral is named for curator Jörgen Langhof (b. 1965), who collected the discovery sample.

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