Quantitative Mineralogical Characterization of Karst Bauxite Deposits in the Southern Apennines, Italy

QEMSCAN® analysis can be applied to bauxite ores, allowing a rapid quantification of mineralogy (including trace detrital phases) and assessment of the individual textural characteristics of the bauxite lithotypes, showing a detailed image of the distribution of economic and non-economic minerals and their intergrowths. The published data on this subject are currently relatively scarce, and are unhelpful for understanding the basic principles and advantages of applying QEMSCAN® analysis to this kind of ore. In this study the QEMSCAN® development work has been applied to the South Italian karst bauxites, which consist of small deposits that are currently uneconomic, but that can be considered as a model analogue for truly economic karst bauxite ores. The representative samples considered for this study come from two different localities: the Matese Mountains and the Caserta district. The mineralogical composition of bauxite has been quantified by combined QEMSCAN® and XRD Rietveld Quantitative Phase Analysis (QPA), as well as with SEM-EDS techniques. Our results show that the QEMSCAN® data allow a detailed textural characterization and add significant information on the major and trace mineral distribution. This methodology can augment or replace other time-consuming quantitative phase analyses for mineralogical studies of bauxites, provided that the SIP (species identification protocol) database has been carefully validated by preliminary use of XRD and SEM-EDS. However, the XRD (QPA) and QEMSCAN® analytical techniques can be complementary for bauxite ore evaluation, and a very powerful tool for exploitation and mineral processing, as shown in several examples. The results obtained with each technique are compared, and the advantages extensively discussed.