Uralolite, Ca2Be4(PO4)3(OH)3∙5H2O: new data and crystal structure
Mereiter, Kurt; Niedermayr, Gerhard; Walter, Franz
European Journal of Mineralogy Volume 6 Number 6 (1994), p. 887 - 896
published: Nov 30, 1994
manuscript accepted: Jun 23, 1994
manuscript received: Jul 6, 1993
ArtNo. ESP147050606011, Price: 29.00 €
Abstract Uralolite from the Weinebene, Koralpe, Carinthia, Austria, has been investigated with respect to morphology, crystal optics, chemical composition, X-ray powder pattern and crystal structure. Uralolite is monoclinic, space group P21/n, with a = 6.550(1), b = 16.005(3), c = 15.969(4) Å, β = 101.64(2)°, V = 1639.6(8) Å3 and Z = 4. The structure refinement yielded R = 0.058 for 1651 reflections. The structure exhibits a novel type of corrugated tetrahedral layer parallel to (010). The layer has the composition [Be4(PO4)3(OH)3]4- and contains S-shaped groups of four corner-sharing BeO4 tetrahedra which link with PO4 tetrahedra to form 3, 4- and 8-membered rings, including the first occurrence of a BeBeBeP ring. Two Ca atoms in CaO5(H2O)2 coordination and a "free" water molecule complete the structure, which is pseudosymmetric and approximates space group C2/c.