Żabińskiite,
ideally Ca[Al0.5(Ta,Nb)0.5](SiO4)O,
a new mineral of the titanite group from the Piława Górna anatectic
pegmatite,
southwestern Poland
Pieczka A
AGH University of Science and Technology, Department
of Mineralogy, Petrography and
Geochemistry
30-059 Kraków,
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
Górna, 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 g·cm-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) Å, b = 8.692(2)Å, c = 6.561(2) Å, α =
89.712(11)º,
β = 113.830(13) º, γ = 90.352(12)º and V
= 366.77 (11) Å3.
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 spectrum of
Żabińskiite
Last updated 21-Dec-2015