Shakhdaraite-(Y), ScYNb2O8, from the Leskhozovskaya granitic pegmatite, the valley of the Shakhdara River, southwestern Pamir, Gorno-Badakhshanskii Autonomous Region, Tajikistan: New mineral description and crystal structure

Pautov, L.A.; Mirakov, M.A.; Sokolova, E.; Day, M.C.; Hawthorne, F.C.; Schodibekov, M.A.; Faiziev, A.R.

Авторы: Pautov L.A., Mirakov M.A., Sokolova E., Day M.C., Hawthorne F.C., Schodibekov M.A., Faiziev A.R.
Журнал: Canadian Mineralogist
Том: 60
Номер: 2
Год издания: 2022
Издательство: Mineralogical Association of Canada
Местоположение издательства: Canada
Первая страница: 369
Последняя страница: 382
DOI: 10.3749/canmin.2000122
Аннотация: Shakhdaraite-(Y), ideally ScYNb2O8, is a new mineral from the Leskhozovskaya miarolitic granitic pegmatite at the Shakhdara River, southwestern Pamir (Tajikistan). Shakhdaraite-(Y) occurs mainly as grains from 10 to 150 lm in size in a near-miarolitic pegmatite complex in association with quartz, albite, pyrochlore-microlite, fersmite, and an unnamed Sc-Nb oxide; only one large, single, well-shaped crystal 200 lm long was found in a small cavity with quartz, albite, bertrandite, pyrochlore, and jarosite. Shakhdaraite-(Y) is black to dark-brown, streak is brown. Luster is vitreous semi-metallic. It is brittle with conchoidal fracture. Mohs hardness is 5. VHN100¼436 kg/mm2. Dcalc.¼5.602 g/cm3. In reflected light, it is light gray and its reflective capacity is moderate to low. Anisotropy is distinct, without color effects. Pleochroism was not observed. Internal reflections are red-brown. Reflectance values were measured in air with SiC as reference material [k(nm), Rmax,Rmin]: 470, 14.6, 13.9; 546, 14.0, 13.4; 589, 13.9, 13.3; 650, 13.8, 13.1. Electron probe microanalysis (WDS mode, 7 points) gives (wt.%): Nb2O5 50.70; Ta2O5 4.52; TiO2 0.08; WO3 0.79; SnO2 1.54; CaO 1.01; Sc2O3 11.35; MnO 1.38; FeO 0.01; Y2O3 12.00; Ce2O3 0.21; Pr2O3 0.04; Nd2O3 0.27; Sm2O3 0.32; Eu2O3 0.07; Gd2O3 0.86; Tb2O3 0.22; Dy2O3 2.07; Ho2O3 0.29; Er2O3 1.33; Tm2O3 0.35; Yb2O3 2.80; Lu2O3 0.32; PbO 0.24; ThO2 1.90; UO2 3.30, total 97.97. The empirical formula of shakhdaraite-(Y) based on O ¼ 8 apfu (atoms per formula unit) is (Nb1.91Sc0.83Y0.53Ta0.10Mn0.10Ca0.09 Yb0.07U4þ 0.06Dy0.06Sn0.05Th0.04Er0.03Gd0.02 W6þ 0.02Pb0.01Ce0.01Nd0.01Sm0.01Tb0.01Ho0.01Tm0.01Lu0.01Ti0.01)R4.00O8, Z ¼ 2.
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Shakhdaraite-(Y), ScYNb2O8, from the Leskhozovskaya granitic pegmatite, the valley of the Shakhdara River, southwestern Pamir, Gorno-Badakhshanskii Autonomous Region, Tajikistan: New mineral description and crystal structureстатья

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