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 > 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 > 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 (<Si–O> = 1.623 Å, <B(1)–O> = 1.485 Å, <B(2)–O> = 1.479 Å, <T–O> = 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) (<M(1)–O> = 2.346 Å, <M(2)–O> = 2.356 Å, <M(3)–O> = 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 Luxembourgite, AgCuPbBi<sub>4</sub>Se<sub>8</sub>, a new mineral species from Bivels, Grand Duchy of Luxembourg

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

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

Shilovite, natural copper(II) tetrammine nitrate, a new mineral species

2015 ◽  
Vol 79 (3) ◽  
pp. 613-623 ◽  
Author(s):  
Nikita V. Chukanov ◽  
Sergey N. Britvin ◽  
Gerhard Möhn ◽  
Igor V. Pekov ◽  
Natalia V. Zubkova ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Chemical Composition ◽  
Infrared Spectrum ◽  
Copper Complex ◽  
New Mineral ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
X Ray ◽  
New Mineral Species ◽  
Mohs Hardness

AbstractThe new mineral shilovite, the first natural tetrammine copper complex, was found in a guano deposit located on the Pabellón de Pica Mountain, near Chanabaya, Iquique Province, Tarapacá Region, Chile. It is associated with halite, ammineite, atacamite (a product of ammineite alteration) and thénardite. The gabbro host rock consists of amphibole, plagioclase and minor clinochlore, and contains accessory chalcopyrite. The latter is considered the source of Cu for shilovite. The new mineral occurs as deep violet blue, imperfect, thick tabular to equant crystals up to 0.15 mm in size included in massive halite. The mineral is sectile. Its Mohs hardness is 2. Dcalc is 1.92 g cm–3. The infrared spectrum shows the presence of NH3 molecules and NO3– anions. Shilovite is optically biaxial (+), α = 1.527(2), β = 1.545(5), γ = 1.610(2). The chemical composition (electron-microprobe data, H calculated from ideal formula, wt.%) is Cu 26.04, Fe 0.31, N 30.8, O 35.95, H 4.74, total 100.69. The empirical formula is H12.56(Cu1.09Fe0.01)N5.87O6.00. The idealized formula is Cu(NH3)4(NO3)2. The crystal structure was solved and refined to R = 0.029 based upon 2705 unique reflections having F > 4σ(F). Shilovite is orthorhombic, space group Pnn2, a = 23.6585(9), b = 10.8238(4), c = 6.9054(3) Å, V = 1768.3(1) Å3, Z = 8. The strongest reflections of the powder X-ray diffraction pattern [d, Å (I,%) (hkl)] are: 5.931 (41) (400), 5.841 (100) (011), 5.208 (47) (410), 4.162 (88) (411), 4.005 (62) (420), 3.462 (50) (002), 3.207 (32) (031), 2.811 (40) (412).

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.

Putnisite, SrCa4Cr83+ (CO3)8SO4(OH)16·25H2O, a new mineral from Western Australia: description and crystal structure

2014 ◽  
Vol 78 (1) ◽  
pp. 131-144 ◽  
Author(s):  
P. Elliott ◽  
G. Giester ◽  
R. Rowe ◽  
A. Pring
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Western Australia ◽  
Empirical Formula ◽  
New Mineral ◽  
Orthorhombic Space Group ◽  
Calculated Density ◽  
X Ray ◽  
Area Detector ◽  
Mohs Hardness

AbstractPutnisite, SrCa4Cr83+ (CO7)8SO4(OH)16·25H2O, is a new mineral from the Polar Bear peninsula, Southern Lake Cowan, Western Australia, Australia. The mineral forms isolated pseudocubic crystals up to 0.5 mm in size in a matrix composed of quartz and a near amorphous Cr silicate. Putnisite is translucent, with a pink streak and vitreous lustre. It is brittle and shows one excellent and two good cleavages parallel to {100}, {010} and {001}. The fracture is uneven and the Mohs hardness 1½−2. The measured density is 2.20(3) g/cm3 and the calculated density based on the empirical formula is 2.23 g/cm3. Optically, putnisite is biaxial negative, with α = 1.552(3), β = 1.583(3) and γ = 1.599(3) (measured in white light). The optical orientation is uncertain and pleochroism is distinct: X pale bluish grey, Y pale purple, Z pale purple. Putnisite is orthorhombic, space group Pnma, with a = 15.351(3), b = 20.421(4) Å, c = 18.270(4) Å, V = 5727(2) Å3 (single-crystal data), and Z = 4. The strongest five lines in the X-ray powder diffraction pattern are [d(Å)(I)(hkl)]: 13.577 (100) (011), 7.659 (80) (200), 6.667 (43) (211), 5.084 (19) (222, 230), 3.689 (16) (411). Electron microprobe analysis (EMPA) gave (wt.%): Na2O 0.17, MgO 0.08, CaO 10.81, SrO 5.72, BaO 0.12, CuO 0.29, Cr2O3 31.13, SO3 3.95, SiO2 0.08, Cl− 0.28, CO2calc 17.94, H2Ocalc 30.30, O=Cl−0.06, total 100.81. The empirical formula, based on O + Cl = 69, is: Cr8.023+Ca3.78Sr1.08Na0.11Cu0.072+Mg0.04Ba0.02[(SO4)0.96(SiO4)0.03]0.99 (CO3)7.98(OH)16.19Cl0.15·24.84H2O. The crystal structure was determined from single-crystal X-ray diffraction data (MoKα, CCD area detector and refined to R1 = 5.84% for 3181 reflections with F0 > 4σF. Cr(OH)4O2 octahedra link by edge-sharing to form an eight-membered ring. A 10-coordinated Sr2+ cation lies at the centre of each ring. The rings are decorated by CO3 triangles, each of which links by corner-sharing to two Cr(OH)4O2 octahedra. Rings are linked by Ca(H2O)4O4 polyhedra to form a sheet parallel to (100). Adjacent sheets are joined along [100] by corner-sharing SO4 tetrahedra. H2O molecules occupy channels that run along [100] and interstices between slabs. Moderate to weak hydrogen bonding provides additional linkage between slabs.

Kitagohaite, Pt7Cu, a new mineral from the Lubero region, North Kivu, Democratic Republic of the Congo

2014 ◽  
Vol 78 (3) ◽  
pp. 739-745 ◽  
Author(s):  
A. R. Cabral ◽  
R. Skála ◽  
A. Vymazalová ◽  
A. Kallistová ◽  
B. Lehmann ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Vickers Hardness ◽  
Democratic Republic ◽  
Mean Value ◽  
New Mineral ◽  
Calculated Density ◽  
Reflected Light ◽  
Republic Of The Congo ◽  
Mohs Hardness ◽  
North Kivu

AbstractKitagohaite, ideally Pt7Cu, is a new mineral from the Lubero region of North Kivu, Democratic Republic of the Congo. The mineral occurs as alluvial grains that were recovered together with other Pt-rich intermetallic compounds and Au. Kitagohaite is opaque, greyish white and malleable and has a metallic lustre and a grey streak. In reflected light, kitagohaite is white and isotropic. The crystal structure of kitagohaite is cubic, space group Fmm, of the Ca7Ge type, with a = 7.7891(3) Å, V = 472.57(5) Å3 and Z = 4. The strongest diffraction lines [d in Å(I)(hkl)] are: 2.246 (100)(222), 1.948(8)(004), 1.377 (77)(044), 1.174(27)(622), 1.123 (31)(444) and 0.893 (13)(662). The Vickers hardness is 217 kg mm−2 (VHN100), which is equivalent to a Mohs hardness of 3½ and the calculated density is 19.958(2) g cm−3. Electron-microprobe analyses gave a mean value (n = 13) of 95.49 wt.% Pt and 4.78 wt.%Cu, which corresponds to Pt6.93Cu1.07 on the basis of eight atoms. The new mineral is named for the Kitagoha river, in the Lubero region.

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.

Staročeskéite, Ag0.70Pb1.60(Bi1.35Sb1.35)Σ2.70S6, from Kutná Hora, Czech Republic, a new member of the lillianite homologous series

2018 ◽  
Vol 82 (4) ◽  
pp. 993-1005 ◽  
Author(s):  
Richard Pažout ◽  
Jiří Sejkora
Keyword(s):  
Czech Republic ◽  
Homologous Series ◽  
Electron Probe ◽  
New Mineral ◽  
Orthorhombic Space Group ◽  
Calculated Density ◽  
New Mineral Species ◽  
Reflected Light ◽  
Ore District ◽  
The Ideal

ABSTRACTA new mineral species, staročeskéite, ideally Ag0.70Pb1.60(Bi1.35Sb1.35)Σ2.70S6, has been found at Kutná Hora ore district, Czech Republic. The mineral occurs in the late-stage Bi-mineralization associated with other lillianite homologues (gustavite, terrywallaceite, vikingite, treasurite, eskimoite and Bi-rich andorite-group minerals) and other bismuth sulfosalts (izoklakeite, cosalite and Bi-rich jamesonite) in quartz gangue. The mineral occurs as lath shaped crystals or anhedral grains up to 80 µm × 70 µm, growing together in aggregates up to 200 µm × 150 µm across. Staročeskéite is steel-grey in colour and has a metallic lustre, the calculated density is 6.185 g/cm3. In reflected light staročeskéite is greyish white; bireflectance and pleochroism are weak with greyish tints. Anisotropy is weak to medium with grey to bluish grey rotation tints. Internal reflections were not observed. The empirical formula based on electron probe microanalyses and calculated on 11 apfu is: (Ag0.68Cu0.01)Σ0.69(Pb1.56Fe0.01Cd0.01)Σ1.58(Bi1.32Sb1.37)Σ2.69(S6.04Se0.01)Σ6.05. The ideal formula is Ag0.70Pb1.60(Bi1.35Sb1.35)Σ2.70S6, which requires Ag 7.22, Pb 31.70, Bi 26.97, Sb 15.72 and S 18.39 wt.%, total 100.00 wt.%. Staročeskéite is a member of the lillianite homologous series with N = 4. Unlike gustavite and terrywallaceite, staročeskéite, similarly to lillianite, is orthorhombic, space group Cmcm, with a = 4.2539(8), b = 13.3094(8), c = 19.625(1) Å, V = 1111.1(2) Å3 and Z = 4. The structure of staročeskéite contains four sulfur sites and three metal sites: one pure Pb site and two mixed sites, M1 (0.52Bi + 0.356Ag + 0.124Sb) and M2 (0.601Sb + 0.259Pb + 0.14Bi). The mineral is characterized by the Bi:Sb ratio 1:1 (Bi/(Bi + Sb) = 0.50) and the Ag+ + Bi3+, Sb3+ ↔ 2 Pb2+ substitution (L%) equal to 70%. Thus the mineral lies between two series of the lillianite structures with N = 4, between the lillianite–gustavite series and the andorite series.

Bicapite, KNa2Mg2(H2PV145+O42)·25H2O, a new polyoxometalate mineral with a bicapped Keggin anion from the Pickett Corral mine, Montrose County, Colorado, U.S.A.

2019 ◽  
Vol 104 (12) ◽  
pp. 1851-1856 ◽  
Author(s):  
Anthony R. Kampf ◽  
John M. Hughes ◽  
Barbara P. Nash ◽  
Joe Marty
Keyword(s):  
Crystal Structure ◽  
Electron Probe ◽  
Structural Unit ◽  
New Mineral ◽  
Charge Balance ◽  
Keggin Anion ◽  
Naturally Occurring ◽  
New Mineral Species ◽  
Mohs Hardness ◽  
Measured Density

Abstract Bicapite, KNa2Mg2(H2PV145+O42)·25H2O, is a new mineral species (IMA2018-048) discovered at the Pickett Corral mine, Montrose County, Colorado, U.S.A. Bicapite occurs as square tablets up to about 0.2 mm on edge on montroseite-corvusite-bearing sandstone. Crystals are dark red-brown, often appearing black. The streak is orange, and the luster is vitreous. Bicapite is brittle, has a Mohs hardness of 1½, and displays one excellent cleavage on {100}. The measured density is 2.44(2) g/cm3. Bicapite is uniaxial (+), ω = 1.785(5), ε ≈ 1.81 (white light); pleochroism is red-brown; E &gt; O, slight. The electron probe microanalysis and results of the crystal structure determination provided the empirical formula (based on 67 O apfu) (K1.23Na2.23Mg1.48)Σ4.94[H2.51P1.02(V13.915+Mo0.076+)Σ13.98O42]·25H2O. Bicapite is tetragonal, I4/m, with a = 11.5446(12) Å, c = 20.5460(14) Å, V = 2738.3(6) Å3, and Z = 2. The strongest four lines in the diffraction pattern are [d in Å (I) (hkl)]: 10.14 (100) (002,101); 2.978 (29) (134,206); 2.809 (11) (305); and 2.583 (11) (420,008). The atomic arrangement of bicapite was solved and refined to R1 = 0.0465 for 1008 independent reflections with I &gt; 2σI. The structural unit is a [H2PV125+O40(V5+O)2]7– heteropolyanion composed of 12 distorted VO6 octahedra surrounding a central PO4 tetrahedron and capped on opposite sides by two VO5 square pyramids; the structural unit is a modification of the α-isomer of the Keggin anion, [XM12O40]n–. Charge balance in the structure is maintained by the [KNa2Mg2(H2O)25]7+ interstitial complex. The name bicapite is in recognition of this being the only known mineral with a structure based on a bicapped Keggin anion. The discovery of bicapite and numerous other natural polyoxometalate compounds in the Colorado Plateau uranium/vanadium deposits make that the most productive region found to date for naturally occurring polyoxometalate compounds.

Proshchenkoite-(Y) from Russia — a new mineral species in the vicanite group: descriptive data and crystal structure

2008 ◽  
Vol 72 (5) ◽  
pp. 1071-1082 ◽  
Author(s):  
G. Raade ◽  
J. D. Grice ◽  
M. Erambert ◽  
P. Kristiansson ◽  
T. Witzke
Keyword(s):  
Crystal Structure ◽  
New Species ◽  
Analytical Data ◽  
New Mineral ◽  
Nuclear Microprobe ◽  
Descriptive Data ◽  
X Ray ◽  
New Mineral Species ◽  
Mohs Hardness ◽  
A New Species

AbstractA REE-bearing fluorosilicate from the Tommot REE-Nb deposit in Yakutia, Russia, described without a name in 1966, is characterized here as a new species, proshchenkoite-(Y), of the vicanite group of borosilicates. Wavelength-dispersive electron probe analyses gave the following empirical formula: Y3.70REE7.54Ca1.55Na1.16Mn0.77Th0.10Pb0.01)Σ14.83(Fe2+0.83Mn0.15Ti0.02)Σ1.00Ca1.00(P0.70Si0.26As0.04)Σ1.00Si0.26B3.20(O34.55F13.45)Σ48. Boron was analysed with a nuclear microprobe method based on the nuclear reaction 11B(p,α)2α. The simplified formula is (Y,REE,Ca,Mn)15(Fe2+,Mn)Ca(P,Si)Si6B3O34F14. The mineral is trigonal, R3m, with a = 10.7527(7) Å, c = 27.4002(18) Å, V = 2743.6(6) Å 3, Z = 3. The crystal structure was refined to Rl = 0.042 for 1819 observed reflections. Proshchenkoite-(Y) is isostructural with okanoganite-(Y), vicanite-(Ce) and hundholmenite-(Y), and the differences in site occupancies are discussed. The strongest six reflections of the X-ray powder-diffraction pattern [dobs in Å, (I), (hkl)] are: 4.441, (36), (202); 3.144, (77), (214); 3.028, (45). (009); 2.968, (100), (027); 1.782, (32), (330); and 1.713, (32), (1.2.14). The mineral is optically uniaxial (—) with ω 1.734(2) and 8 1.728(2). The Mohs hardness is about 5; density measured on material subject to incipient metamictization is 4.72 g/cm3, as compared to Dcalc = 4.955 g/cm3.The result of electron microprobe analyses of alleged okanoganite-(Y) from the type locality in Okanogan County, Washington, USA, is also presented. We find here also that P > Si at one of the sites, whereas the analytical data of Boiocchi et al. (2004) indicate Si > P. Consequently, the mineral we have analysed is the P analogue of okanoganite-(Y), another new species.

Kudryavtsevaite, Na3MgFe3+Ti4O12, a new kimberlitic mineral

2013 ◽  
Vol 77 (3) ◽  
pp. 327-334 ◽  
Author(s):  
S. Anashkin ◽  
A. Bovkun ◽  
L. Bindi ◽  
V. Garanin ◽  
Y. Litvin
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Vickers Hardness ◽  
New Mineral ◽  
Scientific School ◽  
State University ◽  
Orthorhombic Space Group ◽  
Reflected Light ◽  
Black Streak ◽  
Mohs Hardness

AbstractKudryavtsevaite, ideally Na3MgFe3+Ti4O12, is a new mineral from kimberlitic rocks of the Orapa area, Botswana. It occurs as rare prismatic crystals, up to 100 μm m across, associated with Mg-rich ilmenite, freudenbergite and ulvöspinel. Kudryavtsevaite is opaque with a vitreous lustre and shows a black streak. It is brittle; the Vickers hardness (VHN100) is 901 kg mm−2 (range: 876–925) (Mohs hardness ∼6). In reflected light, kudryavtsevaite is moderately bireflectant and very weakly pleochroic from dark grey to a slightly bluish grey. Under crossed polars, it is very weakly anisotropic with greyish-bluish rotation tints. Internal reflections are absent. Reflectance values (%), Rmin and Rmax, are: 21.3, 25.4 (471.1 nm), 20.6, 24.1 (548.3 nm), 20.0, 23.5 (586.6 nm) and 19.1, 22.4 (652.3 nm).Kudryavtsevaite is orthorhombic, space group Pnma, with a = 27.714(1), b = 2.9881(3), c = 11.3564(6) Å, V = 940.5(1) Å3, and Z = 4. The crystal structure [R1 = 0.0168 for 819 reflections with I > 2σ(I)] consists of edge-sharing and corner-sharing chains composed of Mg, Fe3+ and Ti atoms coordinated by six atoms of oxygen and running along the b axis, with Na filling the tunnels formed by the chains. The eight strongest powder-diffraction lines [d in Å (I/I0) (hkl)] are: 7.17 (100) (301), 4.84 (70) (302), 2.973 (35) (901), 2.841 (50) (004), 2.706 (50) (902), 2.541 (50) (312), 2.450 (70) (611), and 2.296 (45) (612). The average results of 12 electron microprobe analyses gave (wt.%): Na2O 16.46(15), CaO 1.01(3), MgO 5.31(5), Fe2O3 22.24(32), Cr2O3 1.05(6), Al2O3 0.03(2), TiO2 53.81(50), total 99.91, corresponding to the empirical formula (Na2.89Ca0.10)Σ2.99(Ti3.67Fe1.523+Mg0.72Cr0.08)Σ5.99O12, or ideally Na3MgFe3+Ti4O12.The new mineral has been approved by the IMA-CNMNC and named for Galina Kudryavtseva (1947–2006), a well known Russian mineralogist and founder of the Diamond Mineralogy Laboratory and scientific school for investigation of diamond mineralogy and geochemistry at the Lomonosov State University in Moscow, Russia.

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