Mckelveyite group minerals – Part 4: Alicewilsonite-(YLa), Na2Sr2YLa(CO3)6  ⋅  3H2O, a new lanthanum-dominant species from the Paratoo mine, Australia

The new mckelveyite group mineral, alicewilsonite-(YLa), Na 2 Sr 2 YLa(CO 3 ) 6 ⋅ 3H 2 O, was found together with kamphaugite-(Y), paratooite-(Y), bastnäsite-(La), and decrespignyite-(Y) coating along fractures in dolomite at the Paratoo copper mine, South Australia, Australia. It occurs as pale pink to colourless pseudohexagonal tabular crystals up to 150 µ m in size. The streak is white; the lustre is vitreous. The mineral has no cleavage. D calc is 3.37 g cm −3 . Alicewilsonite-(YLa) is optically biaxial ( − ), α = 1.556(2), β = 1.582(2), γ = 1.592(2), 2V (meas.) = 60(2)°, 2V (calc.) = 63° (589 nm). The IR spectrum is reported. The composition (wt %, average of seven analyses) is Na 2 O 7.43, CaO 2.00, SrO 18.43, BaO 1.64, Y 2 O 3 9.59, La 2 O 3 11.74, Pr 2 O 3 1.29, Nd 2 O 3 5.74, Sm 2 O 3 0.44, Eu 2 O 3 0.09, Gd 2 O 3 0.95, Dy 2 O 3 1.15, Ho 2 O 3 0.25, Er 2 O 3 0.89, Yb 2 O 3 0.29, CO 2 29.78, H 2 O 6.18, total 97.88. The empirical formula calculated on the basis of six cations with 3 H 2 O molecules is as follows: Na 2.10 Ca 0.31 Sr 1.56 Ba 0.10 Y 0.74 La 0.63 Pr 0.07 Nd 0.30 Sm 0.03 Eu 0.01 Gd 0.04 Dy 0.05 Ho 0.01 Er 0.04 Yb 0.01 (CO 3 ) 5.92 (H 2 O) 3 . The mineral is triclinic, P 1, a = 8.9839(2), b = 8.9728(3), c = 6.7441(2) Å, α = 102.812(2)°, β = 116.424(2)°, γ = 60.128(2)°, and V = 422.17(2) Å 3 and Z = 1. The strongest reflections of the powder X-ray diffraction pattern [ d ,Å( I )(hkl)] are 6.03(43)(001), 4.355(100)(1 1 ‾ 0, 2 ‾ 1 ‾