TERNOVITE (Mg, Ca)Nb_4O_(11) CENTRE DOT nH_2O - A NEW MINERAL FROM CARBONATITES OF THE VUORIYARVI MASSIF (KOLA PENINSULA)

摘要

Ternovite, Mg-dominant analog of hochelagaite and franconite is found in the hydrothermal alteration zones of carbonatites of the Vuoriyarvi massif, Kola Peniusula, Russia, as radiated spherulites. The mineral associated with calcite, magnetite, phlogopite, richterite, apatite, chalcopyrite, zircon, pyrochlore, dolomite, magnesite, serpentine, barite, pyrite, ancylite-(Ce) and belkovite. Color (megascopic) is white. Translucent. Luster silky sheen, brittle. Hardness on Mohs is 3. Biaxial, negative, 2V 39.5(1) deg, #alpha# 1.725(3), #beta# 1.830(5). Dispersionis not observed. No pleochroism D_(meas) 2.95(2) and D_(calc) 2.99(1) g/cm~3. By analogy with hochelagaite and franconite, the mineral is monoclinic, P2/m, P2 or Pm, with a 20.656(6), b 13.062(5), c 6.338(3) A, #beta# 91.90(8) deg, V=1709.1(5)A~3, Z=4. The strongest lines of the powder diffraction pattern (d in A (1) (hkl)) are: 10.33(100)(200), 5.16(7)(400), 4.56(8)(021), 3.15(17)(102), 3.12(15)(102), 3.06(202-bar)(112-bar), 2.503(3)(721, 232-bar), 1.981(4)(10.0.1-bar, 361-bar). Electron probe analysis gave MgO 3.82, CaO 1.54, SrO 0.20, BaO 1.25, Fe_2O_3 0.18, TiO_2 0.14, Nb_2O_5 69.20, H_2O (added to total 100 wt. percent) 23.67, total 100.00 wt. percent. The ideal formula is (Mg, Ca)Nb_4O_(11) centre dot nH_2O. The spectrum includes following bands (in cm~(-1)): 3240, 1670, 940, 920, 882, 678, 585, 547, 390, 355, 324, 300, 288, 278, 246. The mineral in named in honor of V. I. Ternovoi (1928-1980) one of the explorers of the Kola Peninsula.