scholarly journals Hydroxycalciomicrolite, Ca1.5Ta2O6(OH), a new member of the microlite group from Volta Grande pegmatite, Nazareno, Minas Gerais, Brazil

2017 ◽  
Vol 81 (3) ◽  
pp. 555-564 ◽  
Author(s):  
M. B. Andrade ◽  
H. Yang ◽  
D. Atencio ◽  
R. T. Downs ◽  
N. V. Chukanov ◽  
...  
Keyword(s):  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Minas Gerais ◽  
Calculated Density ◽  
Group Mineral ◽  
Cell Parameters ◽  
Mohs Hardness ◽  
Long Range Ordering ◽  
Symmetry Space ◽  
Symmetry Space Group

AbstractHydroxycalciomicrolite, Ca1.5Ta2O6(OH) is a new microlite-group mineral found in the Volta Grande pegmatite, Nazareno, Minas Gerais, Brazil. It occurs as isolated octahedral and as a combination of octahedral and rhombic dodecahedral crystals, up to1.5 mm in size. The crystals are yellow and translucent, with a white streak and vitreous to resinous lustre. The mineral is brittle, with a Mohs hardness of 5–6. Cleavage is not observed and fracture is conchoidal. The calculated density is 6.176 g cm–3. Hydroxycalciomicroliteis isotropic,ncalc.= 2.010. The infrared and Raman spectra exhibit bands due to O–H stretching vibrations. The chemical composition determined from electron microprobe analysis (n= 13) is (wt.%): Na2O 0.36(8), CaO 15.64(13), SnO20.26(3),Nb2O52.82(30), Ta2O578.39(22), MnO 0.12(2), F 0.72(12) and H2O 1.30 (from the crystal structure data), O = F –0.30, total 99.31(32), yielding an empirical formula, (Ca1.48Na0.06Mn0.01)∑1.55(Ta1.88Nb0.11Sn0.01)∑2.00O6.00[(OH)0.76F0.20O0.04].Hydroxycalciomicrolite is cubic, with unit-cell parametersa= 10.4205(1) Å,V= 1131.53(2) Å3andZ= 8. It represents a pyrochlore supergroup, microlite-group mineral exhibitingP4332 symmetry, instead ofFd3m. Thereduction in symmetry is due to long-range ordering of Ca and vacancies on theAsites. This is the first example of such ordering in a natural pyrochlore, although it is known from synthetic compounds. This result is promising because it suggests that other species withP4332or lower-symmetry space group can be discovered and characterized.

scholarly journals Bohseite, ideally Ca4Be4Si9O24(OH4, from the Piława Górna quarry, the Góry Sowie Block, SW Poland

2017 ◽  
Vol 81 (1) ◽  
pp. 35-46 ◽  
Author(s):  
E. Szełęg ◽  
B. Zuzens ◽  
F. C. Hawthorne ◽  
A. Pieczka ◽  
A. Szuszkiewicz ◽  
...  
Keyword(s):  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Close Association ◽  
Calculated Density ◽  
Al Content ◽  
Mohs Hardness ◽  
Sw Poland ◽  
Optic Orientation ◽  
Symmetry Space ◽  
Symmetry Space Group

AbstractBohseite is an orthorhombic calcium beryllium aluminosilicate with variable Al content and an endmember formula Ca4Be4Si9O24(OH4), that was discovered in the Piława Górna quarry in the eastern part of the Góry Sowie Block, ∼50 km southwest of Wrocław, SW Poland. It occurs in a zoned anatectic pegmatite dyke in close association with microcline, Cs-rich beryl, phenakite, helvite, 'lepidolite', probably bertrandite and unidentified Be-containing mica as alteration products after a primary Be mineral, probably beryl. Bohseite forms fan-like or parallel aggregates (up to 0.7 cm) of white, platy crystals (up to 2 mm long) with characteristic striations. It is white with a white streak, is translucent and has a vitreous lustre; it does not fluoresce under ultraviolet light. The cleavage is perfect on {001} and fair on {010}, and neither parting nor twinning was observed. Bohseite is brittle with a splintery fracture and Mohs hardness is 5–6. The calculated density is 2.719 g cm–3. The indices of refraction are α= 1.579, β = 1.580,γ = 1.597, all ±0.002; 2Vobs = 24(3)°, 2Vcalc = 27°; the optic orientation is as follows: X ^ a = 16.1°, Y ^ b = 16.1°, Z // c Bohseite shows orthorhombic diffraction symmetry, space group Cmcm, a = 23.204(6), b = 4.9442(9), c = 19.418(6) Å, V = 2227.7(4) Å3, Z = 4. The crystal structure was refined to an R1 value of 2.17% based on single-crystal data, and the chemical composition was determined by electron-microprobe analysis. Bohseite is isostructural with bavenite. Bohseite was originally approved with an end-member composition of Ca4Be3AlSi9O25(OH)3, but subsequent discovery of compositions with Be > 3.0 apfu led to redefinition of its end-member composition, holotype sample and locality, as reported here. There is extensive solid solution in bavenite–bohseite according to the scheme O(2)OH– + T(4)Si4+ + T(3)Be2+ ↔ O(2)O2– + T(4)Al3++ T(3)Si4+, and a general formula for the bavenite–bohseite minerals may be written as Ca4BexSi9Al4–xO28–x(OH)x, where x ranges from 2–4 apfu: Ca4Be2Si9Al2O26(OH)2 (bavenite) to Ca4Be4Si9O24(OH)4 (bohseite).

scholarly journals Fluorlamprophyllite, Na3(SrNa)Ti3(Si2O7)2O2F2, a new mineral from Poços de Caldas alkaline massif, Morro do Serrote, Minas Gerais, Brazil

2018 ◽  
Vol 82 (1) ◽  
pp. 121-131 ◽  
Author(s):  
Marcelo B. Andrade ◽  
Hexiong Yang ◽  
Robert T. Downs ◽  
Gunnar Färber ◽  
Reynaldo R. Contreira Filho ◽  
...  
Keyword(s):  
Layered Silicate ◽  
Minas Gerais ◽  
New Mineral ◽  
Chemical Formula ◽  
Calculated Density ◽  
Cell Parameters ◽  
New Mineral Species ◽  
Poços De Caldas ◽  
Mohs Hardness ◽  
Alkaline Massif

ABSTRACTA new mineral species, fluorlamprophyllite (IMA2013-102), ideally Na3(SrNa)Ti3(Si2O7)2O2F2, has been found in the Poços de Caldas alkaline massif, Morro do Serrote, Minas Gerais, Brazil. Alternatively, the idealized chemical formula could be written as (SrNa)[(Na3Ti)F2][Ti2(Si2O7)2O2], setting the large interlayer cations before the cations of the layer. Fluorlamprophyllite is the F-analogue of lamprophyllite. It is associated with aegirine, analcime, natrolite, nepheline and microcline. Fluorlamprophyllite crystals are brownish-orange and bladed. The mineral is transparent with a pale yellow streak and an adamantine lustre. It is brittle and has a Mohs hardness of ~3; cleavage is perfect on {100} and no parting was observed. The calculated density is 3.484 g/cm3. Optically, fluorlamprophyllite is biaxial (+), with α = 1.735(7), β = 1.749(7) and γ = 1.775(9) and 2Vmeas = 72(3)°. An electron microprobe analysis produced an average composition (wt.%) (9 points) of Na2O 10.63(30), K2O 0.47(3), SiO2 30.51(13), SrO 18.30(24), MgO 0.81(17), Al2O3 0.23(2), CaO 1.11(7), MnO 5.03(38), TiO2 27.41(87), Fe2O3 2.45(37), F 2.86(23), plus H2O 1.00 (added to bring the total close to 100%), –O = F –1.20, with the total = 98.61%. The elements Nb and Ba were sought, but contents were below microprobe detection limits. The resultant chemical formula was calculated on the basis of 18 (O + F) atoms per formula unit. The addition of 1.00 wt.% H2O brought [F+(OH)] = 2 pfu, yielding (Na2.63Sr1.35Mn0.54Ca0.15Mg0.15K0.08)Σ4.90(Ti2.63Fe0.24Al0.04)Σ2.91Si3.89O16[F1.15(OH)0.85]Σ2.00. The mineral is monoclinic, with space group C2/m and unit-cell parameters a = 19.255(2), b = 7.0715(7), c = 5.3807(6) Å, β = 96.794(2)° and V = 727.5(1) Å3. The structure is a layered silicate inasmuch as the O atoms are arranged in well-defined, though not necessarily close-packed layers.

Wooldridgeite, Na2(P2O7)2(H2O)10: A new mineral from Judkins Quarry, Warwickshire, England

1999 ◽  
Vol 63 (1) ◽  
pp. 13-16 ◽  
Author(s):  
F. C. Hawthorne ◽  
M. A. Cooper ◽  
D. I. Green ◽  
R. E. Starkey ◽  
A. C. Roberts ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Infrared Absorption Spectrum ◽  
Short Wave ◽  
New Mineral ◽  
Calculated Density ◽  
X Ray ◽  
Mohs Hardness ◽  
Unit Formula

AbstractWooldridgeite, ideally Na2(P2O7)2(H2O)10, orthorhombic, a = 11.938(1), b = 32.854(2), c = 11.017(1) Å , V = 4321.2(8) Å3, a:b:c = 0.3634:1:0.3353, space group Fdd2, Z = 8, is a new mineral from Judkins Quarry, Nuneaton, Warwickshire, England. Associated minerals are calcite, chalcopyrite, bornite and baryte. It occurs as equant crystals forming rhombic dipyramids; no twinning was observed. It is transparent blue-green with a very pale-blue streak, a vitreous lustre, and does not fluoresce under long- or short-wave ultraviolet light. Wooldridgeite has a Mohs hardness of 2–3, is brittle with an irregular fracture, and has no cleavage. The calculated density is 2.279 g/cm3. In transmitted light, wooldridgeite is colourless, non-pleochroic, and shows no dispersion. It is biaxial negative with α = 1.508(1), β = 1.511(1), γ = 1.517(1), 2V(meas.) = 76.2(5), 2V(calc.) = 71(10)8, X = b, Y = c, Z = a. The strongest five reflections in the X-ray powder diffraction pattern are [d(Å), (I), (hkl)]: 8.23(30)(040), 6.52(100)(131), 4.05(40)(260), 3.255(40)(262); 2.924(40)(371). Electron-microprobe analysis of wooldridgeite gave P2O5 39.37, CuO 20.24, MgO 0.24, CaO 7.73, Na2O 8.33, K2O 0.17, H2O(calc.) 24.72, sum 100.80 wt.%; the corresponding unit formula (based on 24 anions) is (Na1.96K0.03)Ca1.00(Cu1.85Mg0.04)P4.04O14(H2O)10 where the H2O groups were assigned from knowledge of the crystal structure; the infrared absorption spectrum also indicates the presence of H2O in the structure. The mineral is named for James Wooldridge (1923–1995), a fervent amateur mineral collector who discovered this mineral.

Belakovskiite, Na7(UO2)(SO4)4(SO3OH)(H2O)3, a new uranyl sulfate mineral from the Blue Lizard mine, San Juan County, Utah, USA

2014 ◽  
Vol 78 (3) ◽  
pp. 639-649 ◽  
Author(s):  
A. R. Kampf ◽  
J. Plášil ◽  
A. V. Kasatkin ◽  
J. Marty
Keyword(s):  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
New Mineral ◽  
San Juan ◽  
Uranyl Sulfate ◽  
Calculated Density ◽  
Secondary Alteration ◽  
X Ray ◽  
Mohs Hardness ◽  
San Juan County

AbstractThe new mineral belakovskiite (IMA2013-075), Na7(UO2)(SO4)4(SO3OH)(H2O)3, was found in the Blue Lizard mine, Red Canyon, White Canyon district, San Juan County, Utah, USA, where it occurs as a secondary alteration phase in association with blödite, ferrinatrite, kröhnkite, meisserite and metavoltine. Crystals of belakovskiite are very pale yellowish-green hair-like fibres up to 2 mm long and usually no more than a few mm in diameter. The fibres are elongated on [100] and slightly flattened on {021}. Crystals are transparent with a vitreous lustre. The mineral has a white streak and a probable Mohs hardness of ∼2. Fibres are flexible and elastic, with brittle failure and irregular fracture. No cleavage was observed. The mineral is readily soluble in cold H2O. The calculated density is 2.953 g cm−3. Optically, belakovskiite is biaxial (+) with α = 1.500(1), β = 1.511(1) and γ = 1.523(1) (measured in white light). The measured 2V is 87.1(6)° and the calculated 2V is 88°. The mineral is non-pleochroic. The partially determined optical orientation is X ≈ a. Electron-microprobe analysis provided Na2O 21.67, UO3 30.48, SO3 40.86, H2O 6.45 (structure), total 99.46 wt.% yielding the empirical formula Na6.83(U1.04O2)(SO4)4(S0.99O3OH)(H2O)3 based on 25 O a.p.f.u. Belakovskiite is triclinic, P, with a = 5.4581(3), b = 11.3288(6), c = 18.4163(13) Å, α = 104.786(7)°, β = 90.092(6)°, γ = 96.767(7)°, V = 1092.76(11) Å3 and Z = 2. The eight strongest X-ray powder diffraction lines are [dobs Å(I)(hkl)]: 8.96(35)(002), 8.46(29)(011), 5.19(100)(01,101,10), 4.66(58)(013,02,0,110), 3.568(37)(120,023,005,03), 3.057(59)(06,15,31), 2.930(27)(multiple) and 1.8320(29)(multiple). The structure, refined to R1 = 5.39% for 3163 Fo > 4σF reflections, contains [(UO2)(SO4)4(H2O)]6− polyhedral clusters connected via an extensive network of Na−O bonds and H bonds involving eight Na sites, three other H2O sites and an SO3OH (hydrosulfate) group. The 3-D framework, thus defined, is unique among known uranyl sulfate structures. The mineral is named for Dmitry Ilych Belakovskiy, a prominent Russian mineralogist and Curator of the Fersman Mineralogical Museum.

scholarly journals Natropalermoite, Na2SrAl4(PO4)4(OH)4, a new mineral isostructural with palermoite, from the Palermo No. 1 mine, Groton, New Hampshire, USA

2017 ◽  
Vol 81 (4) ◽  
pp. 833-840 ◽  
Author(s):  
Benjamin N. Schumer ◽  
Hexiong Yang ◽  
Robert T. Downs
Keyword(s):  
New Hampshire ◽  
Powder Diffraction ◽  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Cell Parameter ◽  
New Mineral ◽  
Orthorhombic Space Group ◽  
Calculated Density ◽  
X Ray ◽  
Mohs Hardness

AbstractNatropalermoite, ideally Na2SrAl4(PO4)4(OH)4, the Na-analogue of palermoite, is a new mineral from the Palermo No. 1 mine, Groton, New Hampshire, USA. Associated minerals are palermoite, eosphorite and quartz. Natropalermoite crystal sare prismatic with striations parallel to the direction of elongation (the a axis) up to 200 μm × 50 μm × 45 μm in size. The mineral is colourless, transparent with a white streak and vitreous lustre and is visually indistinguishable from palermoite. It is brittle with subconchoidal fracture and has a Mohs hardness of 5.5. Cleavage is perfect on {001}, fair on {100} and no parting was observed. The calculated density is 3.502 g cm–3. Natropalermoite is biaxial (–), α = 1.624(1), β = 1.641(1), γ = 1.643(1) (589nm), 2Vmeas = 43(4)°, 2Vcalc = 38°. An electron microprobe analysis yielded an empirical formula (based on 20 O apfu) of (Na1.69Li0.31)∑2.00(Sr0.95Mg0.04Ca0.02Ba0.01)∑1.02(Al3.82Mn0.03Fe0.03)∑3.88(P1.01O4)4(OH)4.Natropalermoite is orthorhombic, space group Imcb, a = 11.4849(6), b = 16.2490(7), c = 7.2927(4) Å, V = 1360.95(17) Å3, Z = 4. Natropalermoite is isotypic with palermoite, but substitution of the larger Na for Li results in substantial increase of the b cell parameter. Four of the seven Na–O distances are longer than their equivalents in palermoite, resulting in a more regular 7-fold coordination polyhedron about Na. The eight strongest peaks in the calculated X-ray powder diffraction are [dcalc(Å),Irel%, (hkl)]: [3.128, 100, (321)], [4.907, 68, (121)], [3.327, 48, (022)], [4.689, 45, (220)], [3.078, 45, (202)], [2.453, 38, (242)], [2.636, 35, (411)], [2.174, 35, (422)].

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.

Potassic-jeanlouisite from Leucite Hill, Wyoming, USA, ideally K(NaCa)(Mg4Ti)Si8O22O2: the first species of oxo amphibole in the sodium–calcium subgroup

2019 ◽  
Vol 83 (4) ◽  
pp. 587-593
Author(s):  
Roberta Oberti ◽  
Massimo Boiocchi ◽  
Frank C. Hawthorne ◽  
Giancarlo Della Ventura ◽  
Gunnar Färber
Keyword(s):  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Structure Refinement ◽  
Crystal Structure Refinement ◽  
Unit Cell Parameters ◽  
X Ray ◽  
International Mineralogical Association ◽  
Cell Parameters ◽  
Mineralogical Association ◽  
Sodium Calcium

AbstractPotassic-jeanlouisite, ideally K(NaCa)(Mg4Ti)Si8O22O2, is the first characterised species of oxo amphibole related to the sodium–calcium group, and derives from potassic richterite via the coupled exchange CMg–1W${\rm OH}_{{\rm \ndash 2}}^{\ndash}{} ^{\rm C}{\rm Ti}_1^{{\rm 4 +}} {} ^{\rm W}\!{\rm O}_2^{2\ndash} $. The mineral and the mineral name were approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification, IMA2018-050. Potassic-jeanlouisite was found in a specimen of leucite which is found in the lava layers, collected in the active gravel quarry on Zirkle Mesa, Leucite Hills, Wyoming, USA. It occurs as pale yellow to colourless acicular crystals in small vugs. The empirical formula derived from electron microprobe analysis and single-crystal structure refinement is: A(K0.84Na0.16)Σ1.00B(Ca0.93Na1.02Mg0.04${\rm Mn}_{{\rm 0}{\rm. 01}}^{2 +} $)Σ2.00C(Mg3.85${\rm Fe}_{{\rm 0}{\rm. 16}}^{2 +} $Ni0.01${\rm Fe}_{{\rm 0}{\rm. 33}}^{3 +} {\rm V}_{{\rm 0}{\rm. 01}}^{3 +} $Ti0.65)Σ5.01T(Si7.76Al0.09Ti0.15)Σ8.00O22W[O1.53F0.47]Σ2.00. The holotype crystal is biaxial (–), with α = 1.674(2), β = 1.688(2), γ = 1.698(2), 2Vmeas. = 79(1)° and 2Vcalc. = 79.8°. The unit-cell parameters are a = 9.9372(10), b = 18.010(2), c = 5.2808(5) Å, β = 104.955(2)°, V = 913.1(2) Å3, Z = 2 and space group C2/m. The strongest eight reflections in the powder X-ray pattern [d values (in Å) (I) (hkl)] are: 2.703 (100) (151); 3.380 (87) (131); 2.541 (80) ($\bar 2$02); 3.151 (70) (310); 3.284 (68) (240); 8.472 (59) (110); 2.587 (52) (061); 2.945 (50) (221,$\bar 1$51).

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.

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.

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