Belousovite, KZn(SO4)Cl, a new sulfate mineral from the Tolbachik volcano with apophyllite sheet-topology.

Abstract

ABSTRACTBelousovite, ideally KZn(SO4)Cl, was found in a Yadovitaya fumarole of the Second scoria cone of the North Breach of the Great Tolbachik Fissure Eruption (1975–1976), Tolbachik volcano, Kamchatka Peninsula, Russia. Belousovite occurs as irregularly-shaped grains and in the form of microcrystalline masses associated with kamchatkite, langbeinite, euchlorine, anglesite and zincite. Belousovite is monoclinic,P21/c,a= 6.8904(5),b= 9.6115(7),c= 8.2144(6) Å, β = 96.582(2),V= 540.43(7) Å3andZ= 4 (from single-crystal diffraction data). The eight strongest lines of the powder X-ray diffraction pattern are [dmeasÅ(I)(hkl)]: 6.8451(100)(100), (3.6401)(71)($\bar{1}$21), (3.1592)(84)(1$\bar{1}$2), (3.1218)(41)($\bar{2}$11), (3.1140)(52)(022), (2.9812)(41)(031), (2.9121)(44)(130) and (2.0483)(19)($\bar{3}$12). The chemical composition determined by the electron-microprobe analysis is (wt.%): K2O 19.55, Rb2O 0.58, ZnO 34.85, SO334.65, Cl 14.77, –O = Cl23.34, total 101.06. The empirical formula based on O + Cl = 5 apfu is K0.97Rb0.01Zn1.00S1.01O4.03Cl0.97. The simplified formula is KZn(SO4)Cl. The crystal structure was solved by direct methods and refined toR1= 0.029 on the basis of 1965 independent observed reflections. The structure of belousovite consists of infinite [ZnSO4Cl]–layers and K+ions. [ZnSO4Cl]–layers are formed by corner sharing mixed-ligand ZnO3Cl tetrahedra and SO4tetrahedra. The topology of [ZnSO4Cl]–layers in belousovite is identical to [Si4O10]4–layers in the minerals of the apophyllite group. A review of mixed-ligand ZnOmClncoordination polyhedra in minerals and inorganic compounds is given.