Żabińskiite, ideally Ca[Al0.5(Ta,Nb)0.5](SiO4)O,

a new mineral of the titanite group from the Piława Grna anatectic pegmatite, southwestern Poland


Pieczka A
AGH University of Science and Technology, Department of Mineralogy, Petrography and Geochemistry
30-059 Krakw, Mickiewicza 30, Poland

Hawthorne FC
Department of Geological Sciences, University of Manitoba
Winnipeg
, Manitoba R3T 2N2, Canada


Ma C, Rossman GR,
Division of Geological and Planetary Sciences, California Institute of Technology,
Pasadena, California 91125-2500, USA

Szełęg E
University of Silesia, Faculty of Earth Sciences, Department of Geochemistry, Mineralogy and Petrography, 41-200 Sosnowiec, Będzińska 60, Poland

Szuszkiewicz A, Turniak K
University of Wrocław, Institute of Geological Sciences, 50-204 Wrocław, pl. M. Borna 9, Poland

Nejbert K, Ilnicki SS
University of Warsaw, Faculty of Geology, Institute of Geochemistry, Mineralogy and Petrology,
 02-089 Warszawa, Żwirki and Wigury 93, Poland




Abstract

Żabińskiite, ideally Ca[Al0.5(Ta,Nb)0.5](SiO4)O, was found in a pegmatite at Piława Grna, Lower Silesia, SW Poland. The mineral occurs along with (Ta,Nb,Al) and (Al,F)-bearing titanites, a pyrochlore-supergroup mineral and a K-mica in compositionally inhomogeneous aggregates, ~120 70 μm in size, in a fractured crystal of zircon intergrown with polycrase-(Y) and euxenite-(Y). Żabińskiite is transparent, brittle, brownish, with white streak, vitreous luster and a hardness of ~5 on Mohs scale. The calculated density for the refined crystal is equal to 3.897 gcm-3, but it strongly depends on composition. The mineral is non-pleochroic, biaxial (–), with mean refractive indices ≥ 1.89. The (Ta,Nb)-richest żabińskiite crystal, (Ca0.980Na0.015)Σ=0.995(Al0.340Fe3+0.029Ti0.298V0.001Zr0.001Sn0.005Ta0.251Nb0.081)Σ=1.005[(Si0.988Al0.012)O4.946F0.047(OH)0.007)Σ=5.000]; 63.1 mol% Ca[Al0.5(Ta,Nb)0.5](SiO4)O; is close in composition to earlier described synthetic material. Żabińskiite is triclinic (space-group symmetry A-1) and has unit-cell parameters a = 7.031(2) , b = 8.692(2), c = 6.561(2) , α = 89.712(11), β = 113.830(13) , γ = 90.352(12) and V = 366.77 (11) 3. It is isostructural with triclinic titanite and bond-topologically identical with titanite and other members of the titanite-group minerals. Żabińskiite crystallized along with (Ta,Nb)- and Al-bearing titanites at increasing Ti and decreasing Ta,  Nb and Al activities, synchronously with polycrase-(Y) and euxenite-(Y) from Ca-contamined fluxed melts or early hydrothermal fluids.



Raman

Raman spectrum of Żabińskiite

  Last updated 21-Dec-2015