Abstract
Pilbarite was described by Simpson (1910) from the Wodgina area of the Pilbara goldfields, Western Australia. The mineral occurs as small nodules enclosed in albite in weathered outcrops of tantalite-rich pegmatites. Occasional residual cores of thorogummite indicate that the pilbarite is pseudomorphous after a primary thorium mineral, probably uranoan thorite. Weathering or hydrothermal alteration of the original thorium mineral yielded what Simpson (1930) considered a chemically related series of distinct species—maitlandite, nicolayite, pilbarite, and hydrothorite. Frondel (1953) has shown that maitlandite, nicolayite, and hydrothorite are minor chemical variants of the phase thorogummite. In a later paper Frondel (1956) mentions pilbarite as an ill-defined substance which needs further study.
