Evaluation of grain size distribution of unbroken chromites

Knowledge of prediction of grind size for liberating minerals to recover minerals is very important for mineral processing applications. The grind size for mineral beneficiation can be established by determining the particle size distributions (PSDs) of minerals in an unbroken ore by image analysis. PSDs determined by fractals in natural cataclasites reveals the degree of cataclastic deformation in the chromites. PSDs have been described by relations between particle mass and size, volume and size, number and size and number and mass. Different mathematical formulas and approaches have been suggested to express relationships against size, and total mass/volume/number is given against increasing size (mass/volume/number undersize). In this paper, grain size distribution was estimated from the distribution of mean Feret diameters (dF) of individual grains by image analysis. It was found by fractal evaluation that the relation is not linear and the cataclastic deformation of the chromite ores studied is dominated by extension microstructure due to fragmentation by microfracturing. The suitability of the lognormal distribution function was studied for linearization of number-based size distribution curves measured on polished sections of unbroken samples of five chromite ore types from Turkey. Data analysis revealed that lognormal evaluation of the distribution of the mean Feret diameters (dF) gives excellent fits for all types of chromite samples which have different degree of cataclasis and wide size ranges.