Batievaite-(Y), Y₂Ca₂Ti[Si₂O₇]₂(OH)₂(H₂O)₄, a new mineral from nepheline syenite pegmatite in the Sakharjok massif, Kola Peninsula, Russia

Batievaite-(Y), Y₂Ca₂Ti[Si₂O₇]₂(OH)₂(H₂O)₄, is a new mineral found in nepheline syenite pegmatite in the Sakharjok alkaline massif, Western Keivy, Kola Peninsula, Russia. The pegmatite mainly consists of nepheline, albite, alkali pyroxenes, amphiboles, biotite and zeolites. Batievaite-(Y) is a late-pegmatitic or hydrothermal mineral associated with meliphanite, fluorite, calcite, zircon, britholite-group minerals, leucophanite, gadolinite-subgroup minerals, titanite, smectites, pyrochlore-group minerals, zirkelite, cerianite-(Ce), rutile, behoite, ilmenite, apatite-group minerals, mimetite, molybdenite, and nickeline. Batievaite-(Y) is pale-cream coloured with white streak and dull, greasy or pearly luster. Its Mohs hardness is 5-5.5. No cleavage or parting was observed. The measured density is 3.45(5) g/cm³. Batievaite-(Y) is optically biaxial positive, α 1.745(5), β 1.747(5), γ 1.752(5) (λ 589 nm), 2V_meas. = 60(5) , 2V_calc. = 65 . Batievaite-(Y) is triclinic, space group P-1, a 9.4024(8), b 5.5623(5), c 7.3784(6) Aa, α 89.919(2), β 101.408(2), γ 96.621(2) , V 375.65(6) Aa³ and Z = 1. The eight strongest lines of the X-ray powder diffraction pattern [d(Aa)(I)(hkl)] are: 2.991(100)(11-2), 7.238(36)(00-1), 3.061(30)(300), 4.350(23)(0-1-1), 9.145(17)(100), 4.042(16)(11-1), 2.819(16)(3-10), 3.745(13)(2-10). The chemical composition determined by electron probe microanalysis (EPMA) is (wt.%): Nb₂O₅ 2.25, TiO₂ 8.01, ZrO₂ 2.72, SiO₂ 29.96, Al₂O₃ 0.56, Fe₂O₃ 0.43, Y₂O₃ 11.45, La₂O₃ 0.22, Ce₂O₃ 0.33, Nd₂O₃ 0.02, Gd₂O₃ 0.07, Dy₂O₃ 0.47, Er₂O₃ 1.07, Tm₂O₃ 0.25, Yb₂O₃ 2.81, Lu₂O₃ 0.45, CaO 24.98, MnO 1.31, MgO 0.01, Na₂O 1.13, K₂O 0.02, F 2.88, Cl 0.19, H₂O 6.75 (determined on the basis of crystal structure data), O = (F,Cl) -1.25, total 97.09 wt.%. The empirical formula based on the EPMA and single-crystal structure analyses is (Y_0.81Ca_0.65Mn_0.15Zr_0.12Yb_0.11Er_0.04Fe³⁺_0.04Ce_{0. 02}Dy_0.02Lu_0.02La_0.01Tm_0.01)_Σ2.00((H₂O)_0.75Ca_{0 .70}□_0.55)_Σ2.00Ca_2.00(□_0.61Na_0.25(H₂ O)_0.14)_Σ1.00(Ti_0.76Nb_0.15Zr_0.09)_Σ1.00[(Si_3.91Al_0.09)_Σ4.00O₁₄] ((OH)_1.56F_0.44)_Σ2.00( (H₂O)_1.27F_0.73)_Σ2.00. The infrared spectrum of the mineral contains the following bands (cm^-1): 483, 584, 649, 800, 877, 985, 1630, 1646, 1732, 3426. Batievaite-(Y) belongs to the rosenbuschite group minerals and is the Na-deficient Y-analogue of hainite. The mineral is named in honour of the Russian geologist Iya Dmitrievna Batieva (1922-2007) in recognition of her remarkable contribution into the geology and petrology of metamorphic and alkaline complexes of the Kola Peninsula.