Nomenclature of the Phosphoferrite Structure Type: Refinements of Landesite and Kryzhanovskite

P. B. Moore, T. Araki and A. R. Kampf*
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.

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- 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- 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.

Mineralogical Magazine; June 1980 v. 43; no. 330; p. 789-795; DOI: 10.1180/minmag.1980.043.330.14
© 1980, The Mineralogical Society
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