Effect of particle shape on the gravity and magnetic separation of wollastonite from pyroxene group minerals

Wollastonite is widely used as a reinforcing filler in glass and ceramic applications due to its alkali-free composition, low coefficient of thermal expansion, and needle-like morphology, which enhance mechanical strength, dimensional stability, and thermal resistance. Its suitability is also related to its high CaO and SiO₂ contents and low levels of volatile impurities. This study evaluates the beneficiation performance of shaking table and wet magnetic separation, with particular emphasis on particle shape in addition to particle size, density, and magnetic susceptibility. Shaking table tests increased wollastonite content from 52.1% in the run-of-mine ore to 60.8% in the coarse light product and 75.5% in the fine light product, while reducing Fe₂O₃ to 1.37% and 1.01%, respectively. Wet magnetic separation further improved concentrate quality, producing a non-magnetic product containing 71.8% wollastonite with a reduced Fe₂O₃ content of 0.79%. Quantitative particle shape analysis based on aspect ratio and roundness revealed that elongated, needle-like particles preferentially reported to light and non-magnetic products, whereas more equant particles concentrated in heavy and magnetic fractions. These findings highlight the influence of morphology-driven separation behavior and indicate that controlling particle shape through appropriate grinding strategies can improve selectivity and support high-purity wollastonite production.