Oxycalciomicrolite, (Ca,Na)2(Ta,Nb,Ti)2O6(O,F), a new member of the microlite group (pyrochlore supergroup) from the Paleoproterozoic São João del Rei Pegmatite Province, Minas Gerais state, Brazil

2020 ◽  
pp. 1-5
Author(s):  
Victor H.R. Menezes da Silva ◽  
Ciro A. Ávila ◽  
Reiner Neumann ◽  
Fabiano R.L. Faulstich ◽  
Felipe E.A. Alves ◽  
...  
Keyword(s):  
Electron Microprobe ◽  
Minas Gerais ◽  
Accessory Mineral ◽  
X Ray Diffraction ◽  
Calculated Density ◽  
X Ray ◽  
Cell Parameters ◽  
Wavelength Dispersive Spectrometry ◽  
Minas Gerais State ◽  
Mohs Hardness

Abstract Oxycalciomicrolite (IMA2019-110), (Ca,Na)2(Ta,Nb,Ti)2O6(O,F), is a new member of microlite-group mineral found in the saprolite of the weathered Fumal pegmatite, located close to the city of Nazareno, Minas Gerais state, Brazil. It occurs as an accessory mineral associated with quartz, albite, microcline, muscovite, columbite-subgroup minerals, cassiterite, hematite, ilmenite, monazite-(Ce), xenotime-(Y), zircon, beryl, spinel, epidote and garnet-group minerals. Oxycalciomicrolite is found as octahedral crystals, occasionally modified to rhombododecahedra, ranging from 0.2 to 0.5 mm in size. The crystals are brownish-yellow to brownish-red and translucent, with white streak and vitreous to resinous lustre. The tenacity is brittle, with a Mohs hardness of 5–5½. Cleavage and parting are not observed; the fracture is conchoidal. Electron microprobe analysis, Raman and infrared spectroscopies and X-ray powder diffraction were applied to characterise this mineral. Oxycalciomicrolite is isotropic, ncalc. = 2.037, and the calculated density is 6.333 g/cm3. The composition is (Ca1.57□0.26Na0.06Sn0.03Sr0.03U0.02Mn0.02Fe0.01Ce0.01)∑2.00(Ta1.79Nb0.18Ti0.03)∑2.00O6.00[O0.64F0.19□0.17]∑1.00 analysed by electron microprobe using wavelength dispersive spectrometry. The unit-cell parameters obtained by Pawley fitting from powder X-ray diffraction data are a = 10.4325(4) Å and V = 1135.46(14) Å3 with Z = 8.

Kummerite, Mn2+Fe3+Al(PO4)2(OH)2·8H2O, a new laueite-group mineral from the Hagendorf Süd pegmatite, Bavaria, with ordering of Al and Fe3+

2016 ◽  
Vol 80 (7) ◽  
pp. 1243-1254 ◽  
Author(s):  
I. E. Grey ◽  
E. Keck ◽  
W. G. Mumme ◽  
A. Pring ◽  
C. M. Macrae ◽  
...  
Keyword(s):  
Electron Microprobe ◽  
Empirical Formula ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Calculated Density ◽  
Group Mineral ◽  
X Ray ◽  
Cell Parameters ◽  
Octahedral Sites ◽  
Phosphate Mineral

AbstractKummerite, ideally Mn2+Fe3+A1(PO4)2(OH)2.8H2O, is a new secondary phosphate mineral belonging to the laueite group, from the Hagendorf-Süd pegmatite, Hagendorf, Oberpfalz, Bavaria, Germany. Kummerite occurs as sprays or rounded aggregates of very thin, typically deformed, amber yellow laths. Cleavage is good parallel to ﹛010﹜. The mineral is associated closely with green Zn- and Al-bearing beraunite needles. Other associated minerals are jahnsite-(CaMnMn) and Al-bearing frondelite. The calculated density of kummerite is 2.34 g cm 3. It is optically biaxial (-), α= 1.565(5), β = 1.600(5) and y = 1.630(5), with weak dispersion. Pleochroism is weak, with amber yellow tones. Electron microprobe analyses (average of 13 grains) with H2O and FeO/Fe2O3 calculated on structural grounds and normalized to 100%, gave Fe2O3 17.2, FeO 4.8, MnO 5.4, MgO 2.2, ZnO 0.5, Al2O3 9.8, P2O5 27.6, H2O 32.5, total 100 wt.%. The empirical formula, based on 3 metal apfu is (Mn2+0.37Mg0.27Zn0.03Fe2+0.33)Σ1.00(Fe3+1.06Al0. 94)Σ2.00PO4)1.91(OH)2.27(H2O)7.73. Kummerite is triclinic, P1̄, with the unit-cell parameters of a = 5.316(1) Å, b =10.620(3) Å , c = 7.118(1) Å, α = 107.33(3)°, β= 111.22(3)°, γ = 72.22(2)° and V= 348.4(2) Å3. The strongest lines in the powder X-ray diffraction pattern are [dobs in Å(I) (hkl)] 9.885 (100) (010); 6.476 (20) (001); 4.942 (30) (020); 3.988 (9) (̄110); 3.116 (18) (1̄20); 2.873 (11) (1̄21). Kummerite is isostructural with laueite, but differs in having Al and Fe3+ ordered into alternate octahedral sites in the 7.1 Å trans-connected octahedral chains.

Ferribushmakinite, Pb2Fe3+(PO4)(VO4)(OH), the Fe3+ analogue of bushmakinite from the Silver Coin mine, Valmy, Nevada

2015 ◽  
Vol 79 (3) ◽  
pp. 661-669 ◽  
Author(s):  
A. R. Kampf ◽  
P. M. Adams ◽  
B. P. Nash ◽  
J. Marty
Keyword(s):  
Low Temperature ◽  
Electron Microprobe ◽  
New Mineral ◽  
Secondary Mineral ◽  
X Ray Diffraction ◽  
Calculated Density ◽  
X Ray ◽  
Silver Coin ◽  
Humboldt County ◽  
Mohs Hardness

AbstractFerribushmakinite (IMA2014-055), Pb2Fe3+(PO4)(VO4)(OH), the Fe3+ analogue of bushmakinite, is a new mineral from the Silver Coin mine, Valmy, Iron Point district, Humboldt County, Nevada, USA, where it occurs as a low-temperature secondary mineral in association with plumbogummite, mottramite, Br-rich chlorargyrite and baryte on massive quartz. Ferribushmakinite forms yellow slightly flattened prisms up to 0.2 mm long growing in X and sixling twins. The streak is pale yellow. Crystals are translucent and have adamantine lustre. The Mohs hardness is ∼2, the tenacity is brittle, the fracture is irregular to splintery and crystals exhibit one or two fair cleavages in the [010] zone. The calculated density is 6.154 g/cm3. Electron microprobe analyses provided: PbO 63.69, CaO 0.07, CuO 1.11, Fe2O3 7.63, Al2O3 1.63, V2O5 12.65, As2O5 3.09, P2O58.63, H2O 1.50 (structure), total 100.00 wt.% (normalized). The empirical formula (based on nine O a.p.f.u.) is: (Pb1.99Ca0.01)Σ2.00(Fe0.66Al0.22Cu0.10)Σ0.98(V0.97P0.85As0.19)Σ2.01O7.84(OH)1.16. Ferribushmakinite is monoclinic, P21/m, a = 7.7719(10), b = 5.9060(7), c = 8.7929(12) Å, β = 111.604(8)°, V = 375.24(9) Å3 and Z = 2. The eight strongest lines in the powder X-ray diffraction pattern are [dobs in Å (I)(hkl)]: 4.794(46)(011); 3.245(84)(211); 2.947(100)(020,212,103); 2.743(49)(112); 2.288(30)(220); 1.8532(27)(314,403); 1.8084(27)(multiple); and 1.7204(28)(312,114,321). Ferribushmakinite is a member of the brackebuschite supergroup. Its structure (R1 = 3.83% for 577 Fo > 4σF) differs from that of bushmakinite only in the dominance of Fe3+ over Al in the octahedral site.

Gajardoite, KCa0.5As3+4O6Cl2·5H2O, a new mineral related to lucabindiite and torrecillasite from the Torrecillas mine, Iquique Province, Chile

2016 ◽  
Vol 80 (7) ◽  
pp. 1265-1272 ◽  
Author(s):  
Anthony R. Kampf ◽  
Barbara P. Nash ◽  
Maurizio Dini ◽  
Arturo Molina A. Donoso
Keyword(s):  
Electron Microprobe ◽  
Room Temperature ◽  
New Mineral ◽  
X Ray Diffraction ◽  
Calculated Density ◽  
Secondary Alteration ◽  
X Ray ◽  
Mohs Hardness ◽  
Measured Density ◽  
Irregular Cleavage

AbstractThe new mineral gajardoite (IMA2015-040), KCa0.5As3+4O6Cl2·5H2O, was found at the Torrecillas mine, Iquique Province, Chile, where it occurs as a secondary alteration phase in association with native arsenic, arsenolite,chongite, talmessite and torrecillasite. Gajardoite occurs as hexagonal plates up to ∼100 μm in diameter and 5 μm thick, in rosette-like subparallel intergrowths. Crystals are transparent, with vitreous lustre and white streak. The Mohs hardness is ∼1½, tenacity is brittleand fracture is irregular. Cleavage is perfect on {001}. The measured density is 2.64 g/cm3 and the calculated density is 2.676 g/cm3. Optically, gajardoite is uniaxial (–) with ω = 1.780(3) and ε = 1.570(5) (measured in white light). The mineral is very slowly soluble in H2O and slowly soluble in dilute HCl at room temperature. The empirical formula, determined from electron-microprobe analyses, is (K0.77Ca0.71Na0.05Mg0.05)∑1.58As4O11Cl1.96H9.62.Gajardoite is hexagonal, P6/mmm, a = 5.2558(8), c = 15.9666(18) Å, V = 381.96(13) Å3 and Z = 1. The eight strongest powder X-ray diffraction lines are [dobs Å(I)(hkl)]: 16.00(100)(001), 5.31(48)(003),3.466 (31)(103), 3.013(44)(104), 2.624(51)(006,110,111), 2.353(36)(113), 1.8647(21)(116,205) and 1.4605(17) (119,303,216). The structure, refined to R1 = 3.49% for 169 Fo > 4σF reflections, contains two types of layers. One layer of formulaKAs3+4O6Cl2 consists of two neutral As2O3 sheets, between which are K+ cations and on the outside of which are Cl– anions. This layer is topologically identical to a slice of the lucabindiite structureand similar to a slice of the torrecillasite structure. The second layer consists of an edge-sharing sheet of Ca(H2O)6 trigonal pyramids with isolated H2O groups centred in the hexagonal cavities in the sheet.

Huenite, Cu4Mo3O12(OH)2, a New Copper-molybdenum Oxy-hydroxide Mineral from the San Samuel Mine, Carrera Pinto, Cachiyuyo De Llampos District, CopiapÓ Province, Atacama Region, Chile

2019 ◽  
Vol 57 (4) ◽  
pp. 467-474
Author(s):  
Pietro Vignola ◽  
Nicola Rotiroti ◽  
G. Diego Gatta ◽  
Andrea Risplendente ◽  
Frédéric Hatert ◽  
...  
Keyword(s):  
Close Association ◽  
Short Wave ◽  
Formula Unit ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Calculated Density ◽  
X Ray ◽  
Cell Parameters ◽  
Long Wave ◽  
Mohs Hardness

Abstract Huenite, Cu4Mo3O12(OH)2, is a new copper and molybdenum oxy-hydroxide mineral found in the San Samuel Mine, Carrera Pinto, Cachiyuyo de Llampos district, Copiapó Province, Atacama Region, Chile. This new species forms flattened orthorhombic prisms up to 60–70 μm in size, weakly elongated along [001]. Huenite crystals were found on fractured surfaces of a quartz breccia, forming aggregates 1 mm in diameter in close association with lindgrenite, gypsum, dark grayish-brown tourmaline, and an unknown pale purple phase. The color is very dark reddish-brown, with a strong vitreous to adamantine luster. Its streak is pale reddish-brown to pinkish. The mineral is brittle with an irregular fracture and a Mohs hardness of 3.5–4 with a good cleavage on {010}. Its calculated density is 5.1 g/cm3. The calculated refractive index is 2.18. Huenite is non-fluorescent under 254 nm (short wave) and 366 nm (long wave) ultraviolet light. The empirical formula, calculated on the basis of 3 (Mo+S+Si) atoms per formula unit, is (Cu3.519Fe2+0.403)Σ3.922(Mo2.907S0.090Si0.003)Σ3.000O12·(OH)2.229, with H2O content calculated for a total of 100 wt.%. Huenite is trigonal, with space group P31/c and unit-cell parameters a = 7.653(5) Å, c = 9.411(6) Å, and V = 477.4(5) Å3 for Z = 2. The eight strongest measured powder X-ray diffraction lines are: [d in Å, (I/I0), (hkl)]: 2.974 (100) (112), 1.712 (59.8) (132), 3.810 (50.6) (110), 2.702 (41.2) (022), 2.497 (38.1) (120), 1.450 (37.2) (134), 6.786 (24.9) (010), and 5.374 (24.5) (011). The mineral, which has been approved by the CNMNC under number IMA 2015-122, is named in honor of Edgar Huen.

Twinning and incommensurate modulation in baumoite, Ba0.5[(UO2)3O8Mo2(OH)3](H2O)~3, the first natural Ba uranyl molybdate

2019 ◽  
Vol 83 (4) ◽  
pp. 507-514
Author(s):  
Peter Elliott ◽  
Jakub Plášil ◽  
Václav Petříček ◽  
Jiří Čejka ◽  
Luca Bindi
Keyword(s):  
South Australia ◽  
New Mineral ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Calculated Density ◽  
X Ray ◽  
Cell Parameters ◽  
Orange Yellow ◽  
Incommensurate Modulation ◽  
Mohs Hardness

ABSTRACTBaumoite, Ba0.5[(UO2)3O8Mo2(OH)3](H2O)~3, is a new mineral found near Radium Hill, South Australia, where it occurs in a granite matrix associated with baryte, metatorbernite, phurcalite and kaolinite. Baumoite forms thin crusts of yellow to orange–yellow tabular to prismatic crystals. The mineral is translucent with a vitreous lustre and pale yellow streak. Crystals are brittle, the fracture is uneven and show one excellent cleavage. The Mohs hardness is ~2½. The calculated density is 4.61 g/cm3. Optically, baumoite crystals are biaxial (–), with α = 1.716(4), β = 1.761(4), γ = 1.767(4) (white light); and 2Vcalc= 42.2°. Electron microprobe analyses gave the empirical formula Ba0.87Ca0.03Al0.04U2.97Mo2.02P0.03O22H11.99, based on 22 O atoms per formula unit. The eight strongest lines in the powder X-ray diffraction pattern are [dobsÅ (I) (hkl)]: 9.175(39)(12${\bar 1}$), 7.450(100)(020), 3.554(20)(221), 3.365(31)(004, 202), 3.255(31)(123, 30${\bar 2}$), 3.209(28)(12${\bar 4}$), 3.067(33)(30${\bar 3}$, 222, 32${\bar 2}$) and 2.977(20)(142). Single-crystal X-ray studies (R1= 5.85% for 1892 main reflections) indicate that baumoite is monoclinic, superspace groupX2/m(a0g)0swithX= (0,½,0,½), with unit-cell parameters:a= 9.8337(3),b= 15.0436(5),c= 14.2055(6) Å, β = 108.978(3)°,V= 1987.25(13) Å3andZ= 4. The crystal structure is twinned and incommensurately modulated and is based upon sheets of U6+and Mo6+polyhedra of unique topology. Four independent cationic sites partially occupied by Ba atoms are located between the sheets, together with H2O molecules.

Fluorcalciomicrolite, (Ca,Na,☐)2Ta2O6F, a new microlite-group mineral from Volta Grande pegmatite, Nazareno, Minas Gerais, Brazil

2013 ◽  
Vol 77 (7) ◽  
pp. 2989-2996 ◽  
Author(s):  
M. B. Andrade ◽  
D. Atencio ◽  
A. I. C. Persiano ◽  
J. Ellena
Keyword(s):  
Structure Refinement ◽  
Minas Gerais ◽  
Accessory Mineral ◽  
Charge Balance ◽  
Wavelength Dispersive Spectroscopy ◽  
Calculated Density ◽  
X Ray ◽  
Bond Stretching ◽  
Mohs Hardness ◽  
Bending Modes

AbstractFluorcalciomicrolite, (Ca, Na, ☐)2Ta2O6F, is a new microlite-group, pyrochlore supergroup mineral approved by the CNMNC (IMA 2012-036). It occurs as an accessory mineral in the Volta Grande pegmatite, Nazareno, Minas Gerais, Brazil. Associated minerals include: microcline, albite, quartz, muscovite, spodumene, “lepidolite”, cassiterite, tantalite-(Mn), monazite-(Ce), fluorite, “apatite”, beryl, “garnet” , epidote, magnetite, gahnite, zircon, “tourmaline” , bityite, hydrokenomicrolite, and other microlite-group minerals under study. Fluorcalciomicrolite occurs as euhedral, untwinned, octahedral crystals 0.1–1.5 mm in size, occasionally modified by rhombododecahedral faces. The crystals are colourless and translucent; the streak is white, and the lustre is adamantine to resinous. It does not fluoresce under ultraviolet light. Mohs' hardness is 4½–5, tenacity is brittle. Cleavage is not observed; fracture is conchoidal. The calculated density is 6.160 g/cm3. The mineral is isotropic, ncalc. = 1.992. The Raman spectrum is dominated by bands of B–X octahedral bond stretching and X–B–X bending modes. The chemical composition (n = 6) is (by wavelength dispersive spectroscopy, H2O calculated to obtain charge balance, wt.%): Na2O 4.68, CaO 11.24, MnO 0.01, SrO 0.04, BaO 0.02, SnO20.63, UO20.02, Nb2O53.47, Ta2O576.02, F 2.80, H2O 0.48, O=F–1.18, total 98.23. The empirical formula, based on 2 cations at the B site, is (Ca1.07Na0.81☐0.12)Σ2.00(Ta1.84Nb0.14Sn0.02)Σ2.00[O5.93(OH)0.07]6.00[F0.79(OH)0.21]. The strongest eight X-ray powder-diffraction lines [d in Å (I)(hkl)] are: 5.997(59)(111), 3.138(83)(311), 3.005(100)(222), 2.602(29)(400), 2.004(23)(511), 1.841(23)(440), 1.589(25)(533), and 1.504(24)(444). The crystal structure refinement (R1 = 0.0132) gave the following data: cubic, Fdm, a = 10.4191(6) Å, V = 1131.07(11) Å3, Z = 8.

Tapiaite, Ca5Al2(AsO4)4(OH)4·12H2O, a new mineral from the Jote mine, Tierra Amarilla, Chile

2015 ◽  
Vol 79 (2) ◽  
pp. 345-354 ◽  
Author(s):  
Anthony R. Kampf ◽  
Stuart J. Mills ◽  
Barbara P. Nash ◽  
Maurizio Dini ◽  
Arturo A. Molina Donoso
Keyword(s):  
Empirical Formula ◽  
New Mineral ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Calculated Density ◽  
X Ray ◽  
Cell Parameters ◽  
Interlayer Region ◽  
Mohs Hardness ◽  
Thick Layers

AbstractTapiaite (IMA2014-024), Ca5Al2(AsO4)4(OH)4·12H2O, is a new mineral from the Jote mine, Tierra Amarilla, Copiapó Province, Atacama, Chile. The mineral is a late-stage, low-temperature, secondary mineral occurring with conichalcite, joteite, mansfieldite, pharmacoalumite, pharmacosiderite and scorodite in narrow seams and vughs in the oxidized upper portion of a hydrothermal sulfide vein hosted by volcanoclastic rocks. Crystals occur as colourless blades, flattened on {101} and elongated and striated along [010], up to ∼0.5 mm long, and exhibiting the forms {101}, {101} and {111}. The blades are commonly intergrown in subparallel bundles and less commonly in sprays. The mineral is transparent and has a white streak and vitreous lustre. The Mohs hardness is estimated to be between 2 and 3, the tenacity is brittle, and the fracture is splintery. It has two perfect cleavages on {101} and {101}. The calculated density based on the empirical formula is 2.681 g cm–3. It is optically biaxial (+) with α = 1.579(1), β = 1.588(1), γ = 1.610(1) (white light), 2Vmeas = 66(2)° and 2Vcalc = 66°. The mineral exhibits no dispersion. The optical orientation is X ≈ [101]; Y = b, Z ≈ [101]. The electron-microprobe analyses (average of five) provided: Na2O 0.09, CaO 24.96, CuO 0.73, Al2O3 10.08, Fe2O3 0.19, As2O5 40.98, Sb2O5 0.09, H2 O 23.46 (structure), total 100.58 wt.%. In terms of the structure, the empirical formula (based on 32 O a.p.f.u.) is (Ca4.83Cu0.102+Na0.03)Σ4.96(Al2.14Fe0.033+)Σ2.17[(As3.875+Sb0.015+)Σ3.88O16][(OH)3.76(H2O)0.24]Σ4(H2O)10·2H2O. The mineral is easily soluble in RT dilute HCl. Tapiaite is monoclinic, P21/n, with unit-cell parameters a = 16.016(1), b = 5.7781(3), c = 16.341(1) Å, β = 116.704(8)°, V = 1350.9(2) Å3 and Z = 2. The eight strongest lines in the powder X-ray diffraction pattern are [dobs Å(I)(hkl)]: 13.91(100)(101), 7.23(17)(200,002), 5.39(22)(110,011), 4.64(33)(112,211,303), 3.952(42)(113,311,213), 3.290(35)(214,412,114,411), 2.823(39)(303,315) and 2.753(15)(513,115,121,511). The structure of tapiaite (R1 = 5.37% for 1733 Fo > 4σF) contains Al(AsO4)(OH)2 chains of octahedra and tetrahedra that are topologically identical to the chain in the structure of linarite. CaO8 polyhedra condense to the chains, forming columns, which are decorated with additional peripheral AsO4 tetrahedra. The CaO8 polyhedra in adjacent columns link to one another by corner-sharing to form thick layers parallel to {101} and the peripheral AsO4 tetrahedra link to CaO6 octahedra in the interlayer region, resulting in a framework structure.

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 > 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.

Hrabákite, Ni9PbSbS8, a new member of the hauchecornite group from Příbram, Czech Republic

2021 ◽  
pp. 1-8
Author(s):  
Jiří Sejkora ◽  
Pavel Škácha ◽  
Jakub Plášil ◽  
Zdeněk Dolníček ◽  
Jana Ulmanová
Keyword(s):  
Czech Republic ◽  
Diffraction Data ◽  
New Mineral ◽  
X Ray Diffraction ◽  
Calculated Density ◽  
X Ray ◽  
Reflected Light ◽  
Mohs Hardness ◽  
Cation Sites ◽  
The Ideal

Abstract The new mineral hrabákite (IMA2020-034) was found in siderite–sphalerite gangue with minor dolomite–ankerite at the dump of shaft No. 9, one of the mines in the abandoned Příbram uranium and base-metal district, central Bohemia, Czech Republic. Hrabákite is associated with Pb-rich tučekite, Hg-rich silver, stephanite, nickeline, millerite, gersdorffite, sphalerite and galena. The new mineral occurs as rare prismatic crystals up to 120 μm in size and allotriomorphic grains. Hrabákite is grey with a brownish tint. Mohs hardness is ca. 5–6; the calculated density is 6.37 g.cm–3. In reflected light, hrabákite is grey with a brown hue. Bireflectance is weak and pleochroism was not observed. Anisotropy under crossed polars is very weak (brownish tints) to absent. Internal reflections were not observed. Reflectance values of hrabákite in air (Rmin–Rmax, %) are: 39.6–42.5 at 470 nm, 45.0–47.5 at 546 nm, 46.9–49.2 at 589 nm and 48.9–51.2 at 650 nm). The empirical formula for hrabákite, based on electron-microprobe analyses (n = 11), is (Ni8.91Co0.09Fe0.03)9.03(Pb0.94Hg0.04)0.98(Sb0.91As0.08)0.99S7.99. The ideal formula is Ni9PbSbS8, which requires Ni 47.44, Pb 18.60, Sb 10.93 and S 23.03, total of 100.00 wt.%. Hrabákite is tetragonal, P4/mmm, a = 7.3085(4), c = 5.3969(3) Å, with V = 288.27(3) Å3 and Z = 1. The strongest reflections of the calculated powder X-ray diffraction pattern [d, Å (I)(hkl)] are: 3.6543(57)(200); 3.2685(68)(210); 2.7957(100)(211); 2.3920(87)(112); 2.3112(78)(310); 1.8663(74)(222); and 1.8083(71)(302). According to the single-crystal X-ray diffraction data (Rint = 0.0218), the unit cell of hrabákite is undoubtedly similar to the cell reported for tučekite. The structure contains four metal cation sites, two Sb (Sb1 dominated by Pb2+) and two Ni (with minor Co2+ content) sites. The close similarity in metrics between hrabákite and tučekite is due to similar bond lengths of Pb–S and Sb–S pairs. Hrabákite is named after Josef Hrabák, the former professor of the Příbram Mining College.

Sergevanite, Na15(Ca3Mn3)(Na2Fe)Zr3Si26O72(OH)3·H2O, a new eudialyte-group mineral from the Lovozero alkaline massif, Kola Peninsula

2020 ◽  
Vol 58 (4) ◽  
pp. 421-436 ◽  
Author(s):  
Nikita V. Chukanov ◽  
Sergey M. Aksenov ◽  
Igor V. Pekov ◽  
Dmitriy I. Belakovskiy ◽  
Svetlana A. Vozchikova ◽  
...  
Keyword(s):  
Kola Peninsula ◽  
Structural Data ◽  
New Mineral ◽  
X Ray Diffraction ◽  
Calculated Density ◽  
Eudialyte Group ◽  
Group Mineral ◽  
X Ray ◽  
Mohs Hardness ◽  
Alkaline Massif

ABSTRACT The new eudialyte-group mineral sergevanite, ideally Na15(Ca3Mn3)(Na2Fe)Zr3Si26O72(OH)3·H2O, was discovered in highly agpaitic foyaite from the Karnasurt Mountain, Lovozero alkaline massif, Kola Peninsula, Russia. The associated minerals are microcline, albite, nepheline, arfvedsonite, aegirine, lamprophyllite, fluorapatite, steenstrupine-(Ce), ilmenite, and sphalerite. Sergevanite forms yellow to orange-yellow anhedral grains up to 1.5 mm across and the outer zones of some grains of associated eudialyte. Its luster is vitreous, and the streak is white. No cleavage is observed. The Mohs' hardness is 5. Density measured by equilibration in heavy liquids is 2.90(1) g/cm3. Calculated density is equal to 2.906 g/cm3. Sergevanite is nonpleochroic, optically uniaxial, positive, with ω = 1.604(2) and ε = 1.607(2) (λ = 589 nm). The infrared spectrum is given. The chemical composition of sergevanite is (wt.%; electron microprobe, H2O determined by HCN analysis): Na2O 13.69, K2O 1.40, CaO 7.66, La2O3 0.90, Ce2O3 1.41, Pr2O3 0.33, Nd2O3 0.64, Sm2O3 0.14, MnO 4.15, FeO 1.34, TiO2 1.19, ZrO2 10.67, HfO2 0.29, Nb2O5 1.63, SiO2 49.61, SO3 0.77, Cl 0.23, H2O 4.22, –O=Cl –0.05, total 100.22. The empirical formula (based on 25.5 Si atoms pfu, in accordance with structural data) is H14.46Na13.64K0.92Ca4.22Ce0.27La0.17Nd0.12Pr0.06Sm0.02Mn1.81Fe2+0.58Ti0.46Zr2.67Hf0.04Nb0.38Si25.5S0.30Cl0.20O81.35. The crystal structure was determined using single-crystal X-ray diffraction data. The new mineral is trigonal, space group R3, with a = 14.2179(1) Å, c = 30.3492(3) Å, V = 5313.11(7) Å3, and Z = 3. In the structure of sergevanite, Ca and Mn are ordered in the six-membered ring of octahedra (at the sites M11 and M12), and Na dominates over Fe2+ at the M2 site. The strongest lines of the powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 7.12 (70) (110), 5.711 (43) (202), 4.321 (72) (205), 3.806 (39) (033), 3.551 (39) (220, 027), 3.398 (39) (313), 2.978 (95) (), 2.855 (100) (404). Sergevanite is named after the Sergevan' River, which is near the discovery locality.

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