gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1980.043.330.14 Nomenclature of the Phosphoferrite Structure Type: Refinements of Landesite and Kryzhanovskite Moore P. B. Araki T. Kampf A. R. * Department of the Geophysical Sciences, The University of Chicago, Illinois 60637, USA

Mineralogy-Geology Section, Los Angeles County Museum of Natural History, 900 Exposition Boulevard, Los Angeles, California 90007, USA.

 6 1980 43 330 789 795 7 12 1979 Copyright © 1980, The Mineralogical Society 1980 Synopsis

The ideal end-members reddingite, Mn32+(H2O)3(PO4)2, phosphoferrite, Fe32+(H2O)3(PO4)2, and kryzhanovskite, Fe33+(OH)3(PO4)2 form a complex triple series. Similarities in crystal axes and pronounced differences in site preferences have led to erroneous indexing of the powder data and subsequent errors in cell refinements. Writing the general formula M(1)M(2)2[(H2O),(OH)]3(PO4)2, the following end-member names apply:
M(1) M(2) Name
Fe2+ Fe2+ phosphoferrite
Fe3+ Fe2+ unnamed
Fe3+ Fe3+ kryzhanovskite
Mn2+ Mn2+ reddingite
Fe2+ Mn2+ unnamed
Fe3+ Mn2+ landesite

Type landesite, Ca0.4Mg1.2Mn7.22+Mn0.53+Fe2.73+(OH)3.2(H2O)8.8(PO4)8.0, has a = 9.458(3) Å, b = 10.185(2) Å, c = 8.543(2) Å, space group Pbna. R = 5.2% for 1821 independent reflexions (Mo-Kα radiation). The distance averages are M(1)-O = 2.098 Å, M(2)-O = 2.205 Å, P-O = 1.539 Å. Cotype kryzhanovskite, Ca0.5Mg0.4Mn3.82+Fe7.33+(OH)7.3(H4O)4.7(PO4)8.0, has a = 9.450(2) Å, b = 10.013(2), c = 8.179(2). R = 7.2% for 1,703 independent reflexions (Mo-Kα radiation). The distance averages are M(1)-O = 2.017 Å, M(2)-O = 2.115, P-O = 1.542.

Computed powder pattern intensities from the structure data admitted extensive revisions of earlier published Miller indices and revised powder data are presented.