Abstract

The hexagonal mineral simpsonite, an oxide of aluminum and tantalum or a tantalate from Tabba. Tabba in Western Australia, was described and named by Bowley in 1939. Taylor furnished Laue and Bragg x-ray data at the same time. The mineral as originally identified was assigned a complex formula based upon the analysis of material consisting of a mixture of microlite and simpsonite.

Since the original description appeared, occurrences of an aluminum tantalate have been found in two localities in Brazil along the boundary between the states of Paraíba and Rio Grande do Norte and in Southern Rhodesia at Bikita. X-ray-diffraction studies and optical examination have shown that the fundamental aluminum tantalate is the same in the materials from Western Australia, Brazil, and Southern Rhodesia. In addition Laue photographs have been obtained and correlated with Taylor's original x-ray data. Rotation photographs have been utilized in establishing the lattice constants.

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