• journal_title：American Mineralogist
• Contributor：Fabrizio Nestola ; Alessandro Guastoni ; Fernando Cámara ; Luciano Secco ; Alberto Dal Negro ; Danilo Pedron ; Anton Beran
• Publisher：Mineralogical Society of America
• Date：2009-
• Format：text/html
• Language：en
• Identifier：10.2138/am.2009.3060
• journal_abbrev：American Mineralogist
• issn：0003-004X
• volume：94
• issue：4
• firstpage：487
• section：Articles

Aluminocerite-(Ce), ideally (Ce,Ca)₉Al(SiO₄)₃[SiO₃(OH)]₄(OH)₃, is isostructural with cerite-(Ce) and cerite-(La). The holotype was found at the Ratti quarry, near Baveno, Italy, in millimeter-sized secondary cavities hosted in aplite-pegmatite veins and pods within pink granite. Aluminocerite-(Ce) forms aggregates of pseudo-octahedral to rhombohedral crystals flattened on the c axis. The cotype of aluminocerite-(Ce) was discovered at the Locatelly quarry, also near Baveno, where it occurs in centimeter-sized miarolitic cavities in pink granite. The mineral is pale pink to pink-reddish, with a white streak, and is translucent with a vitreous luster. Aluminocerite-(Ce) is non-fluorescent. The hardness based on the Mohs scale is 5, and the tenacity is brittle. Neither cleavage, fracture, or twinning were observed. Calculated density is 4.675 g/cm³. It is uniaxial, optically positive, with n_o = 1.810–1.816 and n_e = 1.812–1.822 (λ= 589 nm) and non-pleochroic. The average of 15 electron microprobe analyses for the holotype gave (wt%): Ce₂O₃ 23.37; Nd₂O₃ 15.59; La₂O₃ 7.43; Sm₂O₃ 4.38; Pr₂O₃ 3.54; Gd₂O₃ 3.12; Y₂O₃ 1.68; Dy₂O₃ 0.46; Yb₂O₃ 0.07; CaO 8.31; Fe₂O₃ 0.47; Al₂O₃ 2.47; SiO₂ 24.01; and H₂O 3.63 (calculated from crystal-chemical constraints), total 98.53 wt%, corresponding to the empirical formula (Ca_2.60Ce_2.49Nd_1.62La_0.80Sm_0.44Pr_0.38Gd_0.30Y_0.26Dy_0.04Yb_0.01)∑_8.94(Al_0.85³⁺ Fe_0.10³⁺)∑_0.95(SiO₄)₃[SiO₃(OH)]₄ (OH)_3.06, calculated on the basis of Si = 7. Aluminocerite-(Ce) is trigonal, space group R3c, with a =10.645(1), c = 38.019(5) Å, V = 3731 ų. The strongest eight lines in the X-ray powder diffraction pattern are [d in Å (I)(hkl)]: 3.405(27)(122), 3.250(26)(124), 2.914(100)(02,10), 2.647(58)(220), 2.198(40)(03,12), 1.923(34) (238), 1.826(24)(051), and 1.732(46)(03,18). The crystal structure has been refined to R1 = 0.056 for 745 observed reflections. The name is an allusion to the fact that it is the Al-dominant analog of cerite-(Ce).