Summary

gsminmag

Mineralogical Magazine

0026-461X

Mineralogical Society

10.1180/minmag.1974.039.305.10

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

Adusumilli

Maria S.

Department of Geosciences, University of Brasilia Kieft

Netherlands Organization for the Advancement of Pure Research Burke

E. A. J.

Institute of Earth Sciences, Free University, Amsterdam

3 1974

39 305 571 576 9 2 1973

1974

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: {Ca_{0·28}(Yt,Ln)_0·425(Th,U){in0·11}(Ta_0·75Ti_0·62Nb_0·595Fe_{0·05)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.