LABUNTSOVITE-Fe Na_4K_4(Ba, K)_2(Fe, Mg, Mn)_(1+x)Ti_8(Si_4O_(12))_4(O, OH)_8 centre dot 10H_2O AND LABUNTSOVITE-Mg, Na_4K_4(Ba, K)(Mg, Fe)_(1+x)Ti_8(Si_4O_(12))_4(O, OH)_8 centre dot 10H_2O

摘要

Labuntsovite-Fe, a new mineral species of the labuntsovite group and Fe-dominant member of the labuntsovite subgroup, has been found in Khibiny alkaline massif on Mt. Kukisvumchorr in hydrothermally altered urtite as anhedral grains up to 1-2 mm and aggregates up to 0.3-0.5 cm across. Colour orange. Luster vitreous. Translucent or transparent. H = 5. D_(meas) = 2.94 g/cm~3. Optically biaxial, positive; n_p = 1.682, n_m = 1.696, n_g = 1.835, 2V = 32. Monoclinic, space group c2/m, a = 14.249, b = 13.791, c = 7.777 A, #beta# = 116.82, V= 1364 A,~3 Z = 1. Strongest XRD lines (d, A; I): 3.169(100), 3.100(62), 2.585(58), 6.95(56), 3.032(53), 6.34(34), 2.478(25). Chemical composition (wt percent): Na_2O 5.45, K_2O 8.54, SrO 0.10, BaO 8.02, FeO2.41, MgO 0.30, MnO 0.23, Al_2O_3 0.04, SiO_2 39.66, TiO_2 25.61, ZrO_2 0.05, Nb_2O_5 0.11, H_2O 8.20, Total 99.72. Empirical formula: Na_4(K_(3.74)Na_(0.26))_(#SIGMA#4) (Ba_(1.27)K_(0.65)Sr_(0.02)(H_2O)_(2.14)) (Fe_(0.81)~(2+)Mg_(0.18)Mn_(0.08) square_(0.93))_(#SIGMA#2)(Ti_(7.76)Nb_(0.20)Zr_(0.01))_(7.97)(Si_(15.98)Al_(0.02))_(#SIGMA#16)O_(48)(O_(5.43)OH_(2.57))_(#SIGMA#8) centre dot 7.66H_2O. Simplified formula: Na_4K_4(Ba, K)_2(Fe, Mg, Mn)_(1+x)Ti_8(Si_4O_(12))_4(O, OH)_8 centre dot 10H_2O.Labuntsovite-Mg, a new mineral species of the labuntsovite group, Mg-dominant member of the labuntsovite subgroup, has been found in Kovdor massif of ultrabasic alkaline rocks in cavities of vuggy dolomitic carbonatites as 0.3-1 to 1-3 mm prismatic crystals. Colourless, rarely yellowish, pink or light orange. Luster vitreous. Translucent or transparent. H = 5. D_(meas) = 2.88 g/cm~3. Optically biaxial, positive; n_p = 1.688, n_m = 1.698, n_g = 1.804, 2V = 37. Monoclinic, space group C2/m, a = 14.292, b = 13.750, c = 7.792 A, #beta# = 117.03, V = 1364 A~3, Z = 1. Strongest XRD lines (d, A; I): 3.175(100), 3.093(57), 3.083(55), 6.94(51), 3.024(51), 2.576(48), 2.59(38). Chemical composition (wt percent): Na_2O 4.61, K_2O 8.57, CaO 0.03, SrO 0.01, BaO 6.23, FeO 1.49, MgO 1.22, MnO 0.01, Al_2O_3 0.30, SiO_2 39.70, TiO_2 23.96, Nb_2O_5 3.65, H_2O 9.24. Total 99.02. Empirical formula: (Na_(3.57)Ca_(0.01) square_(0.42))_(#SIGMA#4)K_4 (Ba_(0.97)K_(0.37)(H_2O)_(2.18) square_(0.48))_(#SIGMA#4) (Mg_(0.73)Fe_(0.36)~(2+) square_(0.91))_(#SIGMA#2)(Ti_(7.20)Nb_(0.66)Fe_(0.14)~(3+))_(#SIGMA#8)(Si_(15.86)Al_(0.14))_(#SIGMA#16)O_(48)(O_(4.46)OH_(3.54))_(#SIGMA#8) centre dot 8.35H_2O. Simplified formula: Na_4K_4(Ba, K)(Mg, Fe)_(1+x)Ti_8Si_8O_(12))_4(O, OH)_8 centre dot 10H_2O. Both minerals are named in accordance with the suffix nomenclature specially developed for the labuntsovite group and officially adopted by the IMA CNMMN. The position of the new mineral species in this group is shown. Prospects for using suffix systems for naming minerals as a basis for the development of a unified mineralogical nomenclature in future are discussed. Type specimens of both minerals are deposited in the Fersman Mineralogical Museum, Moscow.