Mckelveyite group minerals – Part 2: Alicewilsonite-(YCe), Na₂Sr₂YCe(CO₃)₆ ⋅ 3H₂O, a new species

Abstract. The new mckelveyite group mineral alicewilsonite-(YCe), ideally Na2Sr2YCe(CO3)6 ⋅ 3H2O, was found at Mont Saint-Hilaire, Quebec, Canada, and subsequently the Saint-Amable sill, Khibiny Massif, Kola Peninsula, Russia. Alicewilsonite-(YCe) crystals are commonly hemimorphic pseudotrigonal pseudohexagonal show barrel-shaped, saucer-shaped, spindle-shaped, cone-shaped, columnar, tabular, platy habits. They usually up to 2–3 mm in size with some larger reaching cm. often form stacked or parallel growth aggregates rosettes. colour varies from pale yellow yellow, lemon green orange-yellow, green, grey grey, beige, colourless. streak is white; lustre vitreous. cleavage fair indistinct, (001). Mohs hardness 3. Dcalc 3.37 g cm−3. optically biaxial (+), α=1.554(3), β=1.558(3), γ=1.644(2), 2V (calc.) = 26∘, (meas.) 20(3)∘ (589 nm). IR spectrum reported. composition (wt %, average of six analyses) Na2O 7.42, CaO 0.72, SrO 21.49, BaO 1.41, Y2O3 8.52, La2O3 5.93, Ce2O3 9.52, Pr2O3 0.59, Nd2O3 1.75, Sm2O3 0.46, Gd2O3 0.83, Dy2O3 1.65, Ho2O3 0.34, Er2O3 1.21, Yb2O3 0.64, CO2 29.33, H2O 6.13, total 97.94. empirical formula holotype calculated on basis cations Na2.11Ca0.11Sr1.83Ba0.08Y0.67(Ce0.51La0.32Pr0.03Nd0.09Sm0.02Gd0.04 Dy0.08Ho0.02Er0.06Yb0.03)Σ1.20(CO3)5.88 (H2O)3.00. triclinic, P1, a=9.0036(6) Å, b=9.0175(6) c=6.7712(5) α=102.724(2)∘, β=116.398(2)∘, γ=60.003(2)∘, V=426.46(5) Å3, Z=1. strongest reflections powder X-ray diffraction pattern [d,Å(I)(hkl)] 6.07(31)(001), 4.372(100)(120, 2‾1‾1, 11‾0), 4.037(25)(1‾11, 1‾2‾1, 210), 3.201(25)(121, 2‾1‾2, 11‾1), 2.831(67)(1‾12, 1‾2‾2, 211, 1‾21, 21‾0), 2.601(39)(030, 3‾3‾1,3‾01), 2.236(24)(2‾4‾1, 2‾21, 4‾2‾1). 2.019(23)(003, 2‾22, 2‾4‾2‾, 420). 1.9742(24)(032, 3‾03, 3‾3‾3, 331, 03‾2, 301). crystal structure, solved refined single-crystal data (R1=0.055), weloganite type.