Hard/stiff surface coatings for weakening rock particles - Part II: Evaluation

Size -reduction processes are essential for liberating valuable minerals, yet its low energy efficiency needs to be overcome by developing energy -efficient methods. Accordingly, this study tests the hypothesis that rock particles coated with a relatively stronger/stiffer material may fracture more easily during the size reduction process. The hypothesis was tested by (i) coating soft (talc) and hard (magnetite) mineral particles with a ceramic spray and two inorganic precipitates (CaCO3 and silica), then (ii) assessing whether the fracture strength of coated particles has reduced, as compared with uncoated particles. Also, grinding tests were conducted using uncoated and CaCO3-coated talc samples. Results suggest reduction in the fracture strength as well as faster grinding of soft mineral particles after they are coated. The strength reduction is strongly correlated to the rapid force build-up and crack driving forces in coated talc particles. However, neither SILC nor grinding tests suggest fine fragment generation after coating.