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

The crystal structures have been solved and/or refined for minerals of the alunite and beudantite groups having the general formula AM3(XO4)2(OH)6: that is, Pb(Fe2Cu)(SO4)2(OH)6 [beaverite], PbFe3(SO4)(PO4)(OH)6 [corkite], KAl3(SO4)2(OH)6 [alunite], NaAl3(SO4)2(OH)6 [natroalunite], KFe3(SO4)2(OH)6 [jarosite], SrAl3(SO4)(PO4)(OH)6 [svanbergite] and CaAl3(SO4)(PO4)(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 Cu2+ octahedra. The space group of corkite was found to be the centric R3m rather than the acentric R3m space group reported previously.