THE CRYSTAL STRUCTURE OF FOOTEMINEITE

Abstract

Roscherite, ta manganese and calcium beryllophosphate found in the Greifenstein deposit (Germany), was first described in as a monoclinic mineral (sp. gr. C2/c) with the formula (Ca,Mn,Fe)3Be3(PO4)3 · 2H2O. Using samples from this deposit, we studied the crystal structure of roscherite and its Fe2+-rich analogue. The latter mineral was approved as greifensteinite by the Commission on New Minerals and Mineral Names of International Mineralogical Association (CNMMN IMA). Both roscherite and greifensteinite are isostructural with their Mg-rich analogue zanazziite from the Lavra da Ilha deposit (Minas Gerais, Brazil) and with the Zn-bearing variety of zanazziite [8]. The Fe-dominant (IMA No. 2005-061) and Zn-dominant (IMA No. 2006-028) monoclinic members of the roscherite group were recently approved by the CNMMN IMA as new minerals. The absence of large single crystals prevented structural study of the two latter minerals.