Niobian K-Ba-V Titanates from Micaceous Kimberlite, Star Mine, Orange Free State, South Africa

Roger H. Mitchell and Henry O. A. Meyer
Department of Geology, Lakehead University, Thunder Bay, Ontario P7B 5E1, Canada
Department of Earth and Atmospheric Sciences, Purdue University, West Lafayette, Indiana 47907, U.S.A.

Abstract: Compositional data are presented for Nb-Ba-K-V titanates from micaceous kimberlite (Star mine, S. Africa). These data significantly extend the previously known range of solid solutions in naturally occurring members of the hollandite group. Two distinct suites of crystals occur. One is a suite of primary groundmass prismatic crystals that are Ba-K-V-rich and represent solid-solutions from the priderite series towards mannardite. The second suite consists of anhedral xenocrysts that are Ba-free. In this suite relatively Nb-rich varieties (>4.0% Nb2O5) represent solid-solution towards a niobian-bearing potassian analogue of mannardite, whereas relative Nb-poor (<3.0% Nb2O5) varieties are Nb-bearing vanadian priderites. These hollandite-group minerals have compositions that differ significantly from priderites found in lamproites.

Keywods: K-V-Ba titanate • hollandite • priderite • kimberlite • lamproites • Star mine • South Africa

Mineralogical Magazine; September 1989 v. 53; no. 372; p. 451-456; DOI: 10.1180/minmag.1989.053.372.04
© 1987, The Mineralogical Society
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