Compositional and textural variation in detrital chrome-spinels from the Murray Basin, southeastern Australia

Detrital chrome-spinels are contaminant grains within heavy-mineral concentrates found in the Murray Basin of southeastern Australia. The presence of even minor levels of chromia in the predominantly ilmenite-rich concentrates downgrades their market value as potential feedstocks for the production of titania pigment. Compositions from a database of close to 5000 chrome-spinel analyses show a broad range in chemistry. The major element components and their ranges (wt.%) are Cr: 3.10ÿ52.06, Al: 0.46ÿ32.50, Fe: 3.50ÿ44.48 and Mg: 0.03ÿ15.79. Minor components include; Ti: 0.01ÿ6.41, Zn: 0.00ÿ23.00 and Mn: 0.00ÿ5.82. The broad variation in composition suggests multiple source areas for the chrome-spinels although detailed textural examination indicates that variation has also been introduced through pre- and post-deposition alteration processes. The Murray Basin chrome-spinel database has the potential to be used in interpreting and predicting the effects of various processing conditions used to separate the chrome-spinels from the ilmenite