Crystal structures of alunite family minerals: beaverite, corkite, alunite, natroalunite, jarosite, svanbergite, and woodhouseite

摘要

The crystal structures have been solved and/or refined for minerals of the alunite and beudantite groups having the general formula AM_3(XO_4)_2(OH)_6: that is, Pb(Fe_2Cu)(SO_4)_2(OH)_6 [beaverite], PbFe,(SO_4)(PO_4)(OH)_6 [corkite], KAl_3(SO_4)_2(OH)_6 [alunite], NaAl_3(SO_4)_2(OH)_6 [natroalunite], KFe_3(SO_4)_2(OH)_6 [jarosite], SrAl_3(SO_4)(PO_4)(OH)_6 [svanbergite] and CaAl_3(SO_4)(PO_4) (OH)_6 [woodhouseite]. The structure analyses revealed that the ionic radius of the M site cation affected the a axis length whereas those of the A and X site ions influenced the c axis length. Cu-bearing minerals, osarizawaite and beaverite, showed the Jahn-Teller distortion in the Cu~(2+) octahedra. The space group of corkite was found to be the centric R3m rather than the acentric R3m space group reported previously.