Calcio-ancylite-(Nd), a new REE-carbonate from Baveno, Italy

Calcio-ancylite-(Nd), a new basic hydrated carbonate of calcium and rare earth elements (REE), occurs as pink pine-cone-like crystals in miarolitic cavitieis of Baveno granite, Italy. Electron microprobe anal. yields the formula: (Nd0.90Ce0.64Sm0.33Gd0.28Y0.26Pr0.15Dy00.07Tm0.03)2.80Ca1.20(CO3)3.98(OH) ∞2∞.∞8∞41.01H2O (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)°; measured d. > 4.02 and diffraction pattern are [d (Å), (hkl), I]: 4.26 (100), 100; 2.905, (102), 90; 2.048; (221), 80. The crystal structure refinement (Rw = 0.036) confirms the main features of ancylite-(Ce), but provides evidence for a different distribution of alk. earth and REE in the M sites. A reexamn. of the discredited mineral weibycite from Baveno shows that it is a calcio-ancylite-(Ce) with variable REE content.