Litvinskite Na_2(Na, Mn)Zr[Si_6o_12(OH, O)_6]-A new mineral of the lovozerite group

摘要

Litvinskite, a new mineral of the lovozerite group,has been at Alluaiv Mt, Lovozero alkaline massif, Kola peninsula,Russia. It occurs as isometrical grains up to 7 cm and theirsegregations in aegiringe zone of the large hyperagpaitic pegmatitetogether with microcline, nepheline, sodalite, eudialyte,lomonosovite, ussingite, manganneptunite; replaced by terskite andgaidonnayite. Dark cherry-red to reddish-reddish-brown,transparent. Streak white. Lustre vitreous. Cleavage unperfect,fracture conchoidal. Mohs'hardness ~5. D_meas =2.61, D_calc=2.63g/cm~3. Optically biaxial, negative, 2V<10deg, #alpha#=1.546(1), #beta# =1.574 (1), #gamma# =1.575(1). Chemicalcomposition (wt%): Na_2O_512.43, K_2O 0.11, CaO 0.13, MnO1.61, FeO0.09, Ce_2O_30.09, SiO_3 57.67, TiO_20.19, ZrO_218.85, HfO_2 0.22, Nb_2O_5 0.07, H_2O 8.90, Total 100.36.crystal structure is solved, R =6.49%. monoclinic, space groupCm, unit cell parameters: a =10.589 (7), b =10.217 (8), c=7.355(5)A, #beta# =92.91 (5)deg, V=794.6 (9)A~3. Thelovozerite-like structure. The wide structural formula:(Na_1.54K_0.01(H_2O)_0.47)Na_0.78(Na_0.19Mn~2+_01.4Ca_0.01Fe_0.01)(Zr_0.96Ti_0.01Hf_0.01)[Si_6O_12(OH)_3{(OH)_2.24O_0.76}], simplified formula;Na_2(Na, Mn)Zr[Si_6o_12(OH, O)_6], Z= 2. Strongest reflexesof x-ray powder diagram(d, A=I[hkl]); 7.37—44[110, 001];5.29—100[111,200]. 3.329—74[221,112,310]; 3.238—100[130,221,112]; 2.981—39[131,002,311]; 3.553—37[040,222]. IR spectrum and thermal curves are given. Themineral is named after a crystallographer G. P.Litvinskaya(1920--1994), Moscow University. Type specimen is deposited inFersman Minerealogical Museum of Russian A cademy of Scienced, Moscow.