Crystal structure of litvinskite: A new natural representative of the lovozerite group

A new representative of the lovozerite group-Na, Zr, Mn-silicate litvinskit e (Na, H2O, square)(3)(square, Na, Mn2+)Zr[Si6O12(OH)(3)(OH, O)(3)]-was dis covered in ultraagpaitic pegmatites from the Lovozero massif. The crystal s tructure of the mineral was solved on an automated Syntex P (1) over bar di ffractometer (MoK alpha radiation, 1393 reflections, 2 theta/theta scanning technique, anisotropic refinement to R-hkl = 0.065). The unit-cell paramet ers are a = 10.589(7) Angstrom, b = 10.217(8) Angstrom, c = 7.355(5) Angstr om, beta = 92.91(5)degrees, V = 794.6(9) Angstrom (3), sp. gr. Cm, Z = 2, d (calcd) = 2.63 g/cm(3). The structure of the mineral consist of a three-dim ensional framework of discrete six-membered rings of Si-tetrahedra linked t o isolated Zr-octahedra. The framework cavities are occupied by Na cations. The litvinskite composition and the structure differ from all known natura l and synthetic compounds of the lovozerite group. which supports the assum ption about diversity of mineral types in this group. (C) 2001 MAIK "Nauka/ Interperiodica".