scholarly journals Aluminosugilite, KNa<sub>2</sub>Al<sub>2</sub>Li<sub>3</sub>Si<sub>12</sub>O<sub>30</sub>, an Al analogue of sugilite, from the Cerchiara mine, Liguria, Italy

2020 ◽  
Vol 32 (1) ◽  
pp. 57-66
Author(s):  
Mariko Nagashima ◽  
Chihiro Fukuda ◽  
Takashi Matsumoto ◽  
Teruyoshi Imaoka ◽  
Gianluca Odicino ◽  
...  
Keyword(s):  
Structure Refinement ◽  
Structural Formula ◽  
New Mineral ◽  
Cell Parameters ◽  
Breakdown Spectroscopy ◽  
Granular Crystals ◽  
Cationic Substitution ◽  
Laser Induced Breakdown ◽  
Mohs Hardness ◽  
A Site

Abstract. Aluminosugilite (IMA2018-142), ideal formula KNa2Al2Li3Si12O30, is a new mineral that was found in the interstices in manganiferous metacherts from the Cerchiara mine, Liguria, Italy. Aluminosugilite is an Al analogue of sugilite belonging to the milarite group. It occurs as aggregates of small prismatic and/or granular crystals up to 1 mm in length, and it is pinkish-purple with a pale purple to white streak and a vitreous lustre. It has a Mohs hardness of 6–6.5. Its cleavage is indistinct, poor on (0001). Measured and calculated densities are Dmeas.=2.71–2.72 g cm−3 and Dcalc.=2.73 g cm−3, respectively. Aluminosugilite is optically uniaxial (–), with ω=1.577–1.586 and ε=1.575–1.585, with a weak pleochroism. The magnetic susceptibility is lower than that for sugilite. Aluminosugilite is insoluble in HCl, HNO3 and H2SO4, like sugilite. The empirical formula of aluminosugilite calculated on the basis of O =30 from the result obtained by electron microprobe analysis and laser-induced breakdown spectroscopy is K0.99Na1.99(Al1.38Mn0.313+Fe0.243+Ti0.05Mg0.01)Σ1.99Li3.06Si11.99O30. Structure refinement converged to R1=2.17 %. Its space group is hexagonal P6∕mcc, with unit-cell parameters a=9.9830(4) Å, c=13.9667(5) Å and V=1205.45(7) Å3. Based on the refined site occupancies, the ideal structural formula of aluminosugilite is CKBNa2AAl2T2Li3T1Si12O30. The variation of the A–O3 distance is governed by the cationic substitution at the A site. The a and c dimensions of aluminosugilite are shorter than those of sugilite due to Al substitution for Fe3+ at the A site.

Joanneumite, Cu(C3N3O3H2)2(NH3)2, a new mineral from Pabellón de Pica, Chile and the crystal structure of its synthetic analogue

2017 ◽  
Vol 81 (1) ◽  
pp. 155-166 ◽  
Author(s):  
Hans-Peter Bojar ◽  
Franz Walter ◽  
Judith Baumgartner
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Structure Refinement ◽  
Structural Formula ◽  
New Mineral ◽  
Synthetic Analogue ◽  
X Ray Diffraction ◽  
Calculated Density ◽  
Cell Parameters ◽  
Mohs Hardness

AbstractThe new mineral joanneumite was found at Pabellón de Pica Mountain, Iquique Province, Tarapacá Region, Chile, where it occurs as violet microcrystalline aggregates up to 2 mm in size in small cracks in a gabbroic rock, which is covered by a guano deposit. Associated minerals are salammoniac, dittmarite, möhnite and gypsum. Joanneumite is non-fluorescent and the Mohs hardness is 1. The calculated density is 2.020 g cm–3. The infrared spectrum of joanneumite shows the frequencies of NH3 and isocyanurate groups and the absence of absorptions of H2O molecules and OH– ions. The chemical composition (electron microprobe data, the hydrogen was calculated from the structural formula, wt.%) is C 20.33, N 31.11, O 28.34, Cu 17.27, Zn 0.24, H 2.82, total 100.11. The empirical formula is Cu0.96Zn0.01N7.84C5.98O6.25H9.96 and the idealized formula is CuN8C6O6H10 with the structural formula Cu(C3N3O3H2)2(NH3)2. Due to the lack of suitable single crystals the synthetic analogue of joanneumite was prepared for the single-crystal structure refinement. The crystal structure was solved and refined to R = 0.025 based upon 1166 unique reflections with I > 2σ (I). Joanneumite is triclinic, space group P1̄, a = 4.982(1), b = 6.896(1), c = 9.115(2) Å, α = 90.53(3), β = 97.85(3), γ = 110.08(3)°, V = 290.8(1) Å3, Z = 1 obtained from single-crystal data at 100 K, which are in good agreement with cell parameters from powder diffraction data of joanneumite at 293 K: a = 5.042(1), b = 6.997(1), c = 9.099(2) Å, α = 90.05(3), β = 98.11(2), γ = 110.95(3)° and V = 296.3(1) Å3. The eight strongest lines of the powder X-ray diffraction pattern are [d, Å (I,%) (hkl)] 6.52 (68) (010), 5.15 (47) (011), 4.66 (21) (100, 110), 4.35 (9) (1̄11), 3.29 (6) (1̄20), 3.22 (7) (1̄1̄1), 3.140 (100) (1̄21), 2.074 (7) (1̄32). The crystal structure of joanneumite is identical with the structure of synthetic bis(isocyanurato) diamminecopper(II).

Bassoite, SrV3O7·4H2O, a new mineral from Molinello mine, Val Graveglia, eastern Liguria, Italy

2011 ◽  
Vol 75 (5) ◽  
pp. 2677-2686 ◽  
Author(s):  
L. Bindi ◽  
C. Carbone ◽  
R. Cabella ◽  
G. Lucchetti
Keyword(s):  
Structure Refinement ◽  
Full Professor ◽  
New Mineral ◽  
Monoclinic Space Group ◽  
Calculated Density ◽  
X Ray ◽  
Cell Parameters ◽  
Mohs Hardness ◽  
Dark Green ◽  
The University

AbstractBassoite, ideally SrV3O7·4H2O, is a new mineral from the Molinello manganese mine, Val Graveglia. eastern Liguria, northern Apennines, Italy. It occurs as black euhedral to subhedral grains up to 400 urn across, closely associated with rhodonite, quartz and braunite. Bassoite is opaque with a sub-metallic lustre and a black streak. It is brittle and neither fracture nor cleavage was observed; the Vickers micro-hardness (VHN100) is 150 kg/mm (range 142—165; corresponding to a Mohs hardness of 4—41/2). The calculated density is 2.940 g/cm3 (on the basis of the empirical formula and X-ray single-crystal data). Bassoite is weakly bireflectant and very weakly pleochroic from grey to a dark green. Internal reflections are absent. The mineral is anisotropic, without characteristic rotation tints. Reflectance percentages (Rmin and Rmax) for the four standard COM wavelengths are 18.5%, 19.0% (471.1 nm); 17.2%, 17.8% (548.3 nm); 16.8%, 17.5% (586.6 nm) and 16.2%, 16.8% (652.3 nm), respectively.Bassoite is monoclinic, space group P21/m, with unit-cell parameters: a = 5.313(3) Å, b = 10.495(3) Å, c = 8.568(4) Å, β = 91.14(5)°, V= 477.7(4) Å3, a:b:c = 0.506:1:0.816, and Z = 2. The crystal structure was refined to R1 = 0.0209 for 1148 reflections with Fo > 4σ(Fo) and it consists of layers of VO5 pyramids (with vanadium in the tetravalent state) pointing up and down alternately with Sr between the layers (in nine-fold coordination). The nine most intense X-ray powder-diffraction lines [d in Å (I/I0) (hkt)] are: 8.5663 (100) (001); 6.6363 (14) (011); 3.4399 (14) (1̄21); 3.4049 (17) (121); 2.8339 (15) (1̄22); 2.7949 (11) (122); 2.6550 (15) (200); 2.6237 (11) (040) and 1.8666 (15) (240). Electron microprobe analyses produce a chemical formula (Sr0.97Ca0.02Na0.01)V3.00O74H20, on the basis of 2(Sr+Ca+Na) = 1, taking the results of the structure refinement into account. The presence of water molecules was confirmed by micro-Raman spectroscopy. The name honours Riccardo Basso (b. 1947), full professor of Mineralogy and Crystallography at the University of Genova. The new mineral and mineral name have been approved by the Commission on New Minerals, Nomenclature and Classification, IMA (2011-028).

Oxyplumboroméite, Pb2Sb2O7, a new mineral species of the pyrochlore supergroup from Harstigen mine, Värmland, Sweden

2013 ◽  
Vol 77 (7) ◽  
pp. 2931-2939 ◽  
Author(s):  
U. Hålenius ◽  
F. Bosi
Keyword(s):  
Crystal Structure ◽  
Structure Refinement ◽  
New Mineral ◽  
Crystal Structure Refinement ◽  
Unit Cell Parameters ◽  
Calculated Density ◽  
X Ray ◽  
Cell Parameters ◽  
New Mineral Species ◽  
Mohs Hardness

AbstractOxyplumboroméite, Pb2Sb2O7, is a new mineral of the roméite group of the pyrochlore supergroup (IMA 2013-042). It is found together with calcite and leucophoenicite in fissure fillings in tephroite skarn at the Harstigen mine, Värmland, Sweden. The mineral occurs as yellow to brownish yellow rounded grains or imperfect octahedra. Oxyplumboroméite has a Mohs hardness of ∼5, a calculated density of 6.732 g/cm3 and is isotropic with a calculated refractive index of 2.061. Oxyplumboroméite is cubic, space group Fdm, with the unit-cell parameters a = 10.3783(6) Å, V = 1117.84(11) Å3 and Z = 8. The strongest five X-ray powder-diffraction lines [d in Å(I)(hkl)] are: 2.9915(100)(222), 2.5928(32)(400), 1.8332(48)(440), 1.5638(38)(622) and 1.1900(12)(662). The crystal structure of oxyplumboroméite was refined to an R1 index of 3.02% using 160 unique reflections collected with MoKα radiation. Electron microprobe analyses in combination with crystal-structure refinement, infrared, Mössbauer and electronic absorption spectroscopy resulted in the empirical formula A(Pb0.92Ca0.87Mn0.09Sr0.01Na0.05)Σ1.93B(Sb1.73Fe3+0.27)Σ2.00X+Y[O6.64(OH)0.03]Σ6.67. Oxyplumboroméite is the Pb analogue of oxycalcioroméite, ideally Ca2Sb2O7.

scholarly journals Fluorluanshiweiite, KLiAl1.5□0.5(Si3.5Al0.5)O10F2, a New Mineral of the Mica Group from the Nanyangshan LCT Pegmatite Deposit, North Qinling Orogen, China

Minerals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 93
Author(s):  
Kai Qu ◽  
Xianzhang Sima ◽  
Guowu Li ◽  
Guang Fan ◽  
Ganfu Shen ◽  
...  
Keyword(s):  
Empirical Formula ◽  
Central China ◽  
New Mineral ◽  
Qinling Orogen ◽  
Cell Parameters ◽  
New Mineral Species ◽  
Mohs Hardness ◽  
North Qinling ◽  
Individual Grains ◽  
A Site

A new mineral species of the mica group, fluorluanshiweiite, ideally KLiAl1.5□0.5(Si3.5Al0.5)O10F2, has been found in the Nanyangshan LCT (Li, Cs, Ta) pegmatite deposit in North Qinling Orogen (NQO), central China. Fluorluanshiweiite can be regarded as the F-dominant analogue at the A site of luanshiweiite or the K-dominant analogue at the I site of voloshinite. It appears mostly in cookeite as a flaky residue, replaced by Cs-rich mica, or in the form of scale aggregates. Most individual grains are <1 mm in size, with the largest being ca. 1 cm, and the periphery is replaced by cookeite. No twinning is observed. The mineral is silvery white as a hand specimen, and in a thin section, it appears grayish-white to colorless, transparent with white streaks, with vitreous luster and pearliness on cleavage faces. It is flexible with micaceous fracture; the Mohs hardness is approximately 3; the cleavage is perfect on {001}; and no parting is observed. The measured and calculated densities are 2.94(3) and 2.898 g/cm3, respectively. Optically, fluorluanshiweiite is biaxial (–), with α = 1.554(1), β = 1.581(1), γ = 1.583(1) (white light), 2V(meas.) = 25° to 35°, 2V(calc.) = 30.05°. The calculated compatibility index based on the empirical formula is −0.014 (superior). An electron microprobe analysis yields the empirical formula calculated based on 10 O atoms and 2 additional anions of (K0.85Rb0.12Cs0.02Na0.03)Σ1.02[Li1.05Al1.44(□0.47Fe0.01Mn0.02)Σ0.5] Σ2.99(Si3.55Al0.45) Σ4O10F2, which can be simplified to KLiAl1.5□0.5(Si3.5Al0.5)O10F2. Fluorluanshiweiite is monoclinic with the space group C2/m and unit cell parameters a = 5.2030(5), b = 8.9894(6), c = 10.1253(9) Å, β = 100.68(1)°, and V = 465.37(7) Å3. The strongest eight lines in the X-ray diffraction data are [d in Å(I)(hkl)]: 8.427(25) (001), 4.519(57) (020), 4.121(25) (021), 3.628(61) (112), 3.350(60) (022), 3.091(46) (112), 2.586(100) (130), and 1.506(45) (312).

Arrheniusite-(Ce), CaMg[(Ce7Y3)Ca5](SiO4)3(Si3B3O18)(AsO4)(BO3)F11, a New Member of the Vicanite Group, from the Östanmossa Mine, Norberg, Sweden

2021 ◽  
Author(s):  
Dan Holtstam ◽  
Luca Bindi ◽  
Paola Bonazzi ◽  
Hans-Jürgen Förster ◽  
Ulf B. Andersson
Keyword(s):  
Structure Refinement ◽  
New Mineral ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Calculated Density ◽  
Epma Data ◽  
X Ray ◽  
Cell Parameters ◽  
Greenish Yellow ◽  
The Ideal

ABSTRACT Arrheniusite-(Ce) is a new mineral (IMA 2019-086) from the Östanmossa mine, one of the Bastnäs-type deposits in the Bergslagen ore region, Sweden. It occurs in a metasomatic F-rich skarn, associated with dolomite, tremolite, talc, magnetite, calcite, pyrite, dollaseite-(Ce), parisite-(Ce), bastnäsite-(Ce), fluorbritholite-(Ce), and gadolinite-(Nd). Arrheniusite-(Ce) forms anhedral, greenish-yellow translucent grains, exceptionally up to 0.8 mm in diameter. It is optically uniaxial (–), with ω = 1.750(5), ε = 1.725(5), and non-pleochroic in thin section. The calculated density is 4.78(1) g/cm3. Arrheniusite-(Ce) is trigonal, space group R3m, with unit-cell parameters a = 10.8082(3) Å, c = 27.5196(9) Å, and V = 2784.07(14) Å3 for Z = 3. The crystal structure was refined from X-ray diffraction data to R1 = 3.85% for 2286 observed reflections [Fo &gt; 4σ(Fo)]. The empirical formula for the fragment used for the structural study, based on EPMA data and results from the structure refinement, is: (Ca0.65As3+0.35)Σ1(Mg0.57Fe2+0.30As5+0.10Al0.03)Σ1[(Ce2.24Nd2.13La0.86Gd0.74Sm0.71Pr0.37)Σ7.05(Y2.76Dy0.26Er0.11Tb0.08Tm0.01Ho0.04Yb0.01)Σ3.27Ca4.14]Σ14.46(SiO4)3[(Si3.26B2.74)Σ6O17.31F0.69][(As5+0.65Si0.22P0.13)Σ1O4](B0.77O3)F11; the ideal formula obtained is CaMg[(Ce7Y3)Ca5](SiO4)3(Si3B3O18)(AsO4)(BO3)F11. Arrheniusite-(Ce) belongs to the vicanite group of minerals and is distinct from other isostructural members mainly by having a Mg-dominant, octahedrally coordinated site (M6); it can be considered a Mg-As analog to hundholmenite-(Y). The threefold coordinated T5 site is partly occupied by B, like in laptevite-(Ce) and vicanite-(Ce). The mineral name honors C.A. Arrhenius (1757–1824), a Swedish officer and chemist, who first discovered gadolinite-(Y) from the famous Ytterby pegmatite quarry.

Liudongshengite, Zn4Cr2(OH)12(CO3)·3H2O, a new mineral of the hydrotalcite supergroup, from the 79 mine, Gila County, Arizona, USA

2021 ◽  
Vol 59 (4) ◽  
pp. 763-769
Author(s):  
Hexiong Yang ◽  
Ronald B. Gibbs ◽  
Cody Schwenk ◽  
Xiande Xie ◽  
Xiangping Gu ◽  
...  
Keyword(s):  
Unit Cell ◽  
New Mineral ◽  
Unit Cell Parameters ◽  
Cell Parameters ◽  
New Mineral Species ◽  
General Chemical ◽  
Perfect Cleavage ◽  
Mohs Hardness ◽  
Trivalent Cations ◽  
Positively Charged

ABSTRACT A new mineral species, liudongshengite, ideally Zn4Cr2(OH)12(CO3)·3H2O, has been found in the 79 mine, Gila County, Arizona, USA. It occurs as micaceous aggregates or hexagonal platy crystals (up to 0.10 × 0.10 × 0.01 mm). The mineral is pinkish and transparent with white streak and vitreous luster. It is brittle and has a Mohs hardness of ∼1.5, with perfect cleavage on (001). No twinning or parting is observed macroscopically. The measured and calculated densities are 2.95 (3) and 3.00 g/cm3, respectively. Optically, liudongshengite is uniaxial (−), with ω = 1.720 (8), ε = 1.660 (7) (white light). An electron microprobe analysis, combined with the carbon content measured using an elemental combustion system equipped with mass spectrometry, yielded the empirical formula (Zn3.25Mg0.17Cr2.58)Σ6.00(OH)12(CO3)1.29·3H2O, based on (M2+ + M3+) = 6 apfu, where M2+ and M3+ are divalent and trivalent cations, respectively. Liudongshengite belongs to the quintinite group within the hydrotalcite supergroup and is the Cr-analogue of zaccagnaite-3R, Zn4Al2(OH)12(CO3)·3H2O. It is trigonal, with space group Rm and unit-cell parameters a = 3.1111(4), c = 22.682(3) Å, and V = 190.12(4) Å3. The crystal structure of liudongshengite is composed of positively charged brucite-like layers, [M2+1–xM3+x(OH)2]x+, alternating with negatively charged layers of (CO3)2–·3H2O. Compared to other minerals in the quintinite group, liudongshengite is remarkably enriched in M3+, with an M2+:M3+ ratio of 1.33:1. Like zaccagnaite-3R and many other hydrotalcite-type minerals, liudongshengite may also possess polytypes, as a series of synthetic hydrotalcite-type compounds with a general chemical formula [Zn4Cr2(OH)12]X2·4H2O, where X = Cl–, NO3–, or ½ SO42–, but with unit-cell parameters different from those for liudongshengite, have been reported previously.

Kenoplumbomicrolite, (Pb,□)2Ta2O6[□,(OH),O], a new mineral from Ploskaya, Kola Peninsula, Russia

2018 ◽  
Vol 82 (5) ◽  
pp. 1049-1055 ◽  
Author(s):  
Daniel Atencio ◽  
Marcelo B. Andrade ◽  
Luca Bindi ◽  
Paola Bonazzi ◽  
Matteo Zoppi ◽  
...  
Keyword(s):  
Kola Peninsula ◽  
Northern Region ◽  
Complete Characterization ◽  
New Mineral ◽  
X Ray Diffraction ◽  
International Mineralogical Association ◽  
Cell Parameters ◽  
Mohs Hardness

ABSTRACTThis study presents a complete characterization of kenoplumbomicrolite, (Pb,□)2Ta2O6[□,(OH),O], occurring in an amazonite pegmatite from Ploskaya Mountain, Western Keivy Massif, Kola Peninsula, Murmanskaja Oblast, Northern Region, Russia.Kenoplumbomicrolite occurs in yellowish brown octahedral, cuboctahedral and massive crystals, up to 20 cm, has a white streak, a greasy lustre and is translucent. The Mohs hardness is ~6. Attempts to measure density (7.310–7.832 g/cm3) were affected by the ubiquitous presence of uraninite inclusions. Reflectance values were measured in air and immersed in oil. Kenoplumbocrolite is optically isotropic. The empirical formula is (Pb1.30□0.30Ca0.29Na0.08U0.03)Σ2.00(Ta0.82Nb0.62Si0.23Sn4+0.15Ti0.07Fe3+0.10Al0.01)Σ2.00O6[□0.52(OH)0.25O0.23]Σ1.00 (from the crystal used for the structural study) and (Pb1.33□0.66Mn0.01)Σ2.00(Ta0.87Nb0.72Sn4+0.18Fe3+0.11W0.08Ti0.04)Σ2.00O6[□0.80(OH)0.10O0.10]Σ1.00 (average including additional fragments). The mineral is cubic, space group Fd$\overline 3 $m. The unit-cell parameters refined from powder X-ray diffraction data are a = 10.575(2) Å and V = 1182.6(8) Å3, which are in accord with those obtained previously from a single crystal of a = 10.571(1) Å, V = 1181.3(2) Å3 and Z = 8. The mineral description and its name have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA2015-007a).

scholarly journals Nixonite, Na2Ti6O13, a new mineral from a metasomatized mantle garnet pyroxenite from the western Rae Craton, Darby kimberlite field, Canada

2019 ◽  
Vol 104 (9) ◽  
pp. 1336-1344
Author(s):  
Chiara Anzolini ◽  
Fei Wang ◽  
Garrett A. Harris ◽  
Andrew J. Locock ◽  
Dongzhou Zhang ◽  
...  
Keyword(s):  
Spectroscopic Analysis ◽  
Mantle Xenoliths ◽  
New Mineral ◽  
Monoclinic Space Group ◽  
Calculated Density ◽  
Cell Parameters ◽  
Garnet Pyroxenite ◽  
Mohs Hardness ◽  
Kimberlite Field ◽  
Metasomatized Mantle

Abstract Nixonite (IMA 2018-133), ideally Na2Ti6O13, is a new mineral found within a heavily metasomatized pyroxenite xenolith from the Darby kimberlite field, beneath the west-central Rae Craton, Canada. It occurs as microcrystalline aggregates, 15 to 40 μm in length. Nixonite is isostructural with jeppeite, K2Ti6O13, with a structure consisting of edge- and corner-shared titanium-centered octahedra that enclose alkali-metal ions. The Mohs hardness is estimated to be between 5 and 6 by comparison to jeppeite, and the calculated density is 3.51(1) g/cm3. Electron microprobe wavelength-dispersive spectroscopic analysis (average of 6 points) yielded: Na2O 6.87, K2O 5.67, CaO 0.57, TiO2 84.99, V2O3 0.31, Cr2O3 0.04, MnO 0.01, Fe2O3 0.26, SrO 0.07, total 98.79 wt%. The empirical formula, based on 13 O atoms, is: (Na1.24K0.67Ca0.06)Σ1.97(Ti5.96V0.023Fe0.018)Σ6.00O13 with minor amounts of Cr and Mn. Nixonite is monoclinic, space group C2/m, with unit-cell parameters a = 15.3632(26) Å, b = 3.7782(7) Å, c = 9.1266(15) Å, β = 99.35(15)°, and V = 522.72(1) Å3, Z = 2. Based on the average of seven integrated multi-grain diffraction images, the strongest diffraction lines are [dobs in Å (I in %) (hkl)]: 3.02 (100) (310), 3.66 (75) (110), 7.57 (73) (200), 6.31 (68) (201), 2.96 (63) (311), 2.96 (63) (203), and 2.71 (62) (402). The five main Raman peaks of nixonite, in order of decreasing intensity, are at 863, 280, 664, 135, and 113 cm–1. Nixonite is named after Peter H. Nixon, a renowned scientist in the field of kimberlites and mantle xenoliths. Nixonite occurs within a pyroxenite xenolith in a kimberlite, in association with rutile, priderite, perovskite, freudenbergite, and ilmenite. This complex Na-K-Ti-rich metasomatic mineral assemblage may have been produced by a fractionated Na-rich kimberlitic melt that infiltrated a mantle-derived garnet pyroxenite and reacted with rutile during kimberlite crystallization.

Meieranite, Na2Sr3MgSi6O17, a New Mineral from the Wessels Mine, Kalahari Manganese Fields, South Africa

2019 ◽  
Vol 57 (4) ◽  
pp. 457-466 ◽  
Author(s):  
Hexiong Yang ◽  
Xiangping Gu ◽  
Robert T. Downs ◽  
Stanley H. Evans ◽  
Jaco J. Van Nieuwenhuizen ◽  
...  
Keyword(s):  
South Africa ◽  
Empirical Formula ◽  
Microprobe Analysis ◽  
New Mineral ◽  
Cell Parameters ◽  
New Mineral Species ◽  
General Chemical ◽  
Northern Cape ◽  
Coupled Substitution ◽  
Mohs Hardness

Abstract A new mineral species, meieranite, ideally Na2Sr3MgSi6O17, has been found in the Wessels mine, Kalahari Manganese Fields, Northern Cape Province, South Africa. It occurs in isolated aggregates embedded in a matrix mainly of sugilite, along with minor aegirine and pectolite. Crystals of meieranite are up to 0.5 × 0.5 × 0.4 mm in size. No twinning is observed. The mineral is light blue to blue in transmitted and under incident lights, transparent with white streak, and has vitreous luster. It is brittle and has a Mohs hardness of 5.5; cleavage is good on {010} and no parting was observed. The measured and calculated densities are 3.41(3) and 3.410 g/cm3, respectively. Optically, meieranite is biaxial (–), with α = 1.610(1), β = 1.623(1), γ = 1.630(1) (white light), 2V (meas.) = 70(1)°, 2V (calc.) = 72°. The calculated compatibility index based on the empirical formula is –0.007 (superior). An electron microprobe analysis yields an empirical formula (based on 17 O apfu) of Na1.96(Sr2.91Ba0.03Ca0.03Pb0.02)Σ2.99(Mg0.62Mn0.28Co0.07Fe0.01)Σ0.98Si6.03O17, which can be simplified to Na2Sr3MgSi6O17. Meieranite is orthorhombic, with space group P21nb and unit-cell parameters a 7.9380(2), b 10.4923(3), c 18.2560(6) Å, and V 1520.50(8) Å3. Its crystal structure is characterized by two kinds of layers that alternate along [010]: layers of corner-sharing SiO4 and M2+O4 tetrahedra (M2+ = Mg, Mn, Co, Fe) and layers of NaO6 and SrO8 polyhedra. The tetrahedral layers consist of eight-, five-, and four-membered rings and are composed of [Si6O17] ribbons (parallel to [101]) linked together by MO4 tetrahedra. Most remarkably, the structure of meieranite is topologically identical to that of the nordite group of minerals, which has the general chemical formula Na3SrR3+M2+Si6O17, where R = Ce and La and M = Zn, Fe, and Mn. Accordingly, chemically, meieranite may be obtained through the coupled substitution of 2Sr2+ for (Na+ + R3+) in nordite.

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.

Sign in / Sign up

Export Citation Format

Share Document