Tantal-Aeschynite, a New Mineral of the Aeschynite Group from the Borborema Region, North-Eastern Brazil

Maria S. Adusumilli, C. Kieft and E. A. J. Burke
Department of Geosciences, University of Brasilia
Netherlands Organization for the Advancement of Pure Research
Institute of Earth Sciences, Free University, Amsterdam

Summary: Tantal-aeschynite occurs as idiomorphic metamict crystals in the Raposa pegmatite at São José do Sabugí, Paraíba State, NE. Brazil. Morphological data, microscopic properties, and differential thermal analysis results are given. Electron-microprobe analyses yielded a formula: {Ca0·28}(Yt,Ln)0·425(Th,U){in0·11(Ta0·75Ti0·62Nb0·595Fe0·05)O6. Yttrium is the predominant rare-earth element, with cerium and neodymium as most abundant lanthanides. The tantal-aeschynite unit cell has (after heating) {ita 5·34, b 10·97, c 7·38 Å. An indexed X-ray powder pattern (similar to that of aeschynite) is presented.

Mineralogical Magazine; March 1974 v. 39; no. 305; p. 571-576; DOI: 10.1180/minmag.1974.039.305.10
© 1974, The Mineralogical Society
Mineralogical Society (www.minersoc.org)