Amableite-(Ce), Na15[(Ce1.5Na1.5)Mn3]Mn2Zr3□Si[Si24O69(OH)3](OH)2⋅H2O, a new eudialyte-group mineral from Saint-Amable Sill, Québec, Canada

The new eudialyte-group mineral amableite-(Ce), ideally Na-15[(Ce1.5Na1.5)Mn-3]Mn2Zr3 square Si[Si24O69(OH)(3)](OH)(2)& sdot;H2O, was discovered in a peralkaline pegmatite at Saint-Amable Sill, Mont & eacute;r & eacute;gie, Qu & eacute;bec, Canada. The associated minerals are albite, microcline, aegirine, serandite, natrolite, yofortierite, and an unidentified titanosilicate forming minute grains. Amableite-(Ce) occurs as yellow equant or thick tabular crystals up to 2 mm across. The observed crystal forms are {0001}; the subordinate forms are {110}, {101}, and {100}. Amableite-(Ce) is brittle, with a Mohs hardness of 5. D(meas) = 2.89(1), D(calc) = 2.899 g & sdot;cm(-3). Amableite-(Ce) is optically anomalously biaxial (+) with alpha approximate to beta = 1.603(2) and gamma = 1.608(2). The chemical composition is (wt.%, electron microprobe, H2O measured by means of a modified Penfield method): Na2O 14.20, K2O 0.41, CaO 1.89, MnO 8.25, Fe2O3 2.40, La2O3 3.10, Ce2O3 4.19, Pr2O3 0.16, Nd2O3 0.59, SiO2 49.41, ZrO2 11.17, HfO2 0.24, TiO2 0.68, Nb-2 & Ocy;(5) 1.54, Cl 0.26, H2O 1.70, -O equivalent to Cl -0.06, total 100.13. The crystal structure was determined using single-crystal X-ray diffraction data and refined to R1 = 0.0423. Amableite-(Ce) is trigonal, space group R3, with a = 14.1340(3) & Aring;, c = 30.3780(11) & Aring; and V = 5255.6(3) & Aring;(3). The crystal-chemical formula is (Na12.93K0.27Ce0.06)(Sigma 13.26)[(Mn2.49Ce0.30Ca0.21)(Sigma 3.00)(Ce1.14Na1.04Ca0.82)(Sigma 3.00)](Mn1.05Fe0.90 square(1.05))(Sigma 3.00)(Zr2.85Ti0.12Hf0.03)(Sigma 3.00)(square 0.40Nb0.36Si0.24)(Sigma 1.00)(Si-0.88 square(0.12))(Sigma 1.00)[Si-24(O-70.44(OH)(1.56))(Sigma 72.00)][(OH)(2.20)(H2O)(1.27)]Sigma Cl-3.47(0.22) (Z = 3). Infrared and Raman spectra are given. The strongest lines of the powder X-ray diffraction pattern [d, & Aring; (I, %)(hkl)] are: 11.34 (51)(101), 7.06 (76)(110), 4.312 (63)(205), 3.783 (38)(033), 3.538 (43)(027, 220), 2.963 (84)(45), 2.837 (100)(404). The mineral is named after the discovery locality.