Bastnasite-(Ce) at the Nkombwa Hill carbonatite complex, Isoka District, northeast Zambia

Within the Nkombwa Hill carbonatite complex, bastnasite-(Ce), (Ce,La)CO3F, has been identified as an abundant mineral in xenoliths hosted by late-stage ferrocarbonatite sills and dykes. Bastnasite-(Ce) occurs as fibrous yellow crystals, about 1 mu m in size, replacing monazite and in association with baryte, in a matrix of dolomite. In common with bastnasite-(Ce) from other locations, the bastnasite-(Ce) of Nkombwa Hill contains up to 70% RE2O3, almost entirely as light rare-earth oxides. However, Nkombwa Hill bastnasite-(Ce) is relatively deficient in La and enriched in Pr and Nd.