Characterization of feldspar texture and liberation by automated image analysis

The textural characteristics of an aplite ore that contains albite plus microcline as the feldspar minerals and quartz plus muscovite as the gangue minerals were studied by automated image analysis to identify conditions for the extraction of the feldspar-group minerals for application in the ceramic industry. Automated image analysis provides the large amount of quantitative mineralogical data that is required to evaluate the behaviour of the ore during grinding. The images were acquired on polished surfaces by measuring back-scattered electron signals produced with a microprobe. Minerals were identified hom X-ray spectra and discriminated by grey level and element-characteristic X-rays. The quantities and size distributions of the minerals were determined by measurements on thin sections of the unbroken ore to predict the grind required to liberate the feldspar-group minerals. The ore was then ground to -1.7 mm and polished sections, prepared from sieved fractions of the ground material, were analysed to determine the quantities of mineral species and the apparent total liberation achieved for the feldspar-group minerals. The predicted and measured liberations were compared and the behaviour of the ore during grinding was interpreted from the measured liberation values.