Abstract
Kristiansenite, ideally Ca2ScSn(Si2O7)(Si2O6OH), a rare late-stage hydrothermal Sc-bearing sorosilicate mineral, was found in a gadolinite-fergusonite-type pegmatite of the MI-REE subclass related to the Karkonosze granite, exposed in a quarry at Szklarska Poręba, Lower Silesia, Poland. Kristiansenite occurs in an association with andradite, epidote, allanite-(Ce), titanite, fersmite, scheelite, Sc-bearing columbite-(Fe), a YNbO4 mineral as fergusonite-(Y) or fergusonite-(Y)-beta, silesiaite and wolframite. Single-crystal study of the mineral (R1 of 4.96%), with composition Ca2.00(Sn0.97Sc0.69Fe3+0.17Mn0.05Ti0.04Zr0.03Nb0.02Al0.02Ta0.01)Σ2(Si2O7)[(Si1.98Al0.02)Σ2O6.03(OH)0.97], corroborates its triclinic structure with space group-symmetry C1, Z = 2, and unit-cell parameters a = 10.0304(5), b = 8.4056(4), c = 13.3228(6) Å, α = 90.001(3), β = 109.105(3), γ = 89.997(3)° and V = 1061.40(9) Å3. In the structure of the mineral, the Ca and Si sites are dominantly occupied with Ca and Si, whereas the M1–M4 sites are disordered. The M3 and M4 sites are occupied dominantly by Sn and subordinately Sc, whereas the M1 and M2 sites are occupied dominantly by Sc and subordinately by remaining occupants, including Sn.
Highlights
Kristiansenite, ideally Ca2 ScSn(Si2 O7 )(Si2 O6 OH), is a rare Sc-bearing sorosilicate mineral ofNb-Y-F (NYF) type pegmatites first found in a pegmatite of the amazonite–cleavelandite type at Heftetjern, Tørdal, Telemark, Norway [1]
Výravsky et al [5] noted the presence of kristiansenite in the intragranitic NYF-affilliated pegmatite Kožichovice II, Třebíč pluton, Czech Republic, as a product of late Ca metasomatism of the primary thortveitite, Sc2 Si2 O7
We discuss the crystal chemistry and structure of kristiansenite found in a NYF-affiliated pegmatite in the Szklarska Poreba Huta quarry in Lower Silesia, southwestern Poland, related to post-magmatic stages in the Karkonosze granite intrusion
Summary
Kristiansenite, ideally Ca2 ScSn(Si2 O7 )(Si2 O6 OH), is a rare Sc-bearing sorosilicate mineral of. Nb-Y-F (NYF) type pegmatites first found in a pegmatite of the amazonite–cleavelandite type at Heftetjern, Tørdal, Telemark, Norway [1]. The mineral was found in pegmatites from the Italian Alps in the Baveno region (Locatelli quarry and Seula mine [2,3]), and in a granitic pegmatite from Cadalso de los Vidrios near Madrid, Spain [4]. The crystal structure of type kristiansenite from Norway (triclinic; space group-symmetry C1, Z = 2) was solved by Ferraris et al [6]. We discuss the crystal chemistry and structure of kristiansenite found in a NYF-affiliated pegmatite in the Szklarska Poreba Huta quarry in Lower Silesia, southwestern Poland, related to post-magmatic stages in the Karkonosze granite intrusion
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