Calcio-ancylite-(Nd), a new basic hydrated carbonate of calcium and REE, occurs as pink pine-cone-like crystals in miarolitic cavities of Baveno granite, Italy. Electron microprobe analysis yields the formula: (Nd0.90Co0.64Sm0.33Gd0.28Y0.26Pr0.15La0.14Dy0.07 Tm0.03) Σ=2.80 Ca1.20(CO3)3.98(OH)2.84.1.01H2O (Z = 1). The mineral is monoclinic, Pm11, with a = 4.976(2), b = 8.468(2), c = 7.212(2) Å, α = 90.04(3)°; dmeas > 4.02 and dcalc = 4.08 g/cm3; hardness (Mohs) 4-4.5; biaxial (-). A re-examination of the discredited mineral "weibyeite' from Baveno shows that it is a calcio-ancylite (Ce) with variable REE content.
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