Crystal structure of the hydrated sulphate pickeringite (MgAl2(SO4)4· 22H2O): X-ray powder diffraction study
Quartieri, Simona; Triscari, Maurizio; Viani, Alberto
European Journal of Mineralogy Volume 12 Number 6 (2000), p. 1131 - 1138
published: Nov 17, 2000
manuscript accepted: May 2, 2000
manuscript received: Oct 20, 1999
ArtNo. ESP147051206005, Price: 29.00 €
Abstract The crystal structure of pickeringite (ideal formula MgAh(SO4)4 . 22H2O) from Roccalumera (Messina, Italy), a hydrated sulphate of the halotrichite group, has been determined by X-ray powder diffraction with the Rietveld method. The space group has been confmned to be P21/c with unit cell parameters: a = 6.1844(2) Å, b = 24.2715(9) Å, c = 21.2265(7) A and ß = l00.326(4)°. The comparison of these powder data with those reported in the PDF-2 database (12-299) evidences strong differences in both the cell parameters and Bragg reflection positions, suggesting the redefinition of the PDF card for this mineral. The results of the Rietveld refinement confirm the close correspondence between the structures of pickeringite and apjohnite (MnAI2(SO4)4 . 22H2O).