Reference:
▪ Pieczka, A., Hawthorne, F.C., Ma, C., Rossman, G.R., Szełęg, E., Szuszkiewicz, A., Turniak, K., Nejbert, K., Ilnicki, S.S., Buffat, P., Rutkowski, B. (2017): Żabińskiite, ideally Ca(Al0.5Ta0.5)(SiO4)O, a new mineral of the titanite group from the Piława Górna pegmatite, the Góry Sowie Block, southwestern Poland. Mineralogical Magazine, 81, 591–610.
Abstract:
Żabińskiite, ideally Ca(Al0.5Ta0.5)(SiO4)O, was found in a Variscan granitic pegmatite at Piława Górna, Lower Silesia, SW Poland. The mineral occurs along with (Al,Ta,Nb)- 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 a white streak, vitreous luster and a hardness of ~5 on Mohs scale. The calculated density for the refined crystal is equal 44 to 3.897 g·cm-3, but strongly depends on composition. The mineral is non-pleochroic, biaxial (–), with mean refractive indices ≥ 1.89. The (Al,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]; 60.7 mol% Ca[Al0.5(Ta,Nb)0.5](SiO4)O; is close in composition to previously 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 minerals of the titanite group. Żabińskiite crystallized along with (Al,Ta,Nb)-bearing titanites at increasing Ti and Nb, and decreasing Ta activities, almost coevally with polycrase-(Y) and euxenite-(Y) from Ca contaminated fluxed melts or early hydrothermal fluids.
▪ Pieczka, A., Hawthorne, F.C., Ma, C., Rossman, G.R., Szełęg, E., Szuszkiewicz, A., Turniak, K., Nejbert, K., Ilnicki, S.S., Buffat, P., Rutkowski, B. (2017): Żabińskiite, ideally Ca(Al0.5Ta0.5)(SiO4)O, a new mineral of the titanite group from the Piława Górna pegmatite, the Góry Sowie Block, southwestern Poland. Mineralogical Magazine, 81, 591–610.
Abstract:
Żabińskiite, ideally Ca(Al0.5Ta0.5)(SiO4)O, was found in a Variscan granitic pegmatite at Piława Górna, Lower Silesia, SW Poland. The mineral occurs along with (Al,Ta,Nb)- 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 a white streak, vitreous luster and a hardness of ~5 on Mohs scale. The calculated density for the refined crystal is equal 44 to 3.897 g·cm-3, but strongly depends on composition. The mineral is non-pleochroic, biaxial (–), with mean refractive indices ≥ 1.89. The (Al,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]; 60.7 mol% Ca[Al0.5(Ta,Nb)0.5](SiO4)O; is close in composition to previously 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 minerals of the titanite group. Żabińskiite crystallized along with (Al,Ta,Nb)-bearing titanites at increasing Ti and Nb, and decreasing Ta activities, almost coevally with polycrase-(Y) and euxenite-(Y) from Ca contaminated fluxed melts or early hydrothermal fluids.