Value added industrial minerals production from calcite-rich wollastonite

The worldwide consumption of wollastonite has been increasing from day to day. It is a calcium metasilicate with the chemical formula CaSiO₃. Wollastonite is the only naturally occurring, non-metallic, white mineral that is needle-shaped in a crystal habit. Due to its high chemical and thermal resistance and nontoxic properties, wollastonite replaces asbestos. Apart from this, the acicular property of wollastonite allow it to compete with other acicular materials where improvements in dimensional stability, flexural modulus and heat deflection are sought. Due to its unique properties such as: its high brightness and whiteness, low moisture and oil absorption, low volatile content, and acicular properties, it is used also as a filling material for ceramics, plastics and paints, thermal and electrical insulator, wetting agent and smelter for glaze. Three methods are used for the beneficiation of wollastonite: mechanical sorting, dry or wet magnetic separation and flotation. Magnetic separation and flotation can be applied together in some cases. In this study, flotation has been investigated for the selective separation of calcite-rich wollastonite ores from the Buzlukdağ deposit, in the Kırşehir-Akpınar region, in the middle of Anatolia. The mineralogical analysis of the sample used in the study shows that the ore sample contains 60–62% wollastonite (CaSiO₃), 4–5% augite (Ca,Na)(Mg,Fe,Al)(Si,Al)₂O₆, 30–32% calcite (CaCO₃) and minor amount of other minerals. As a result of this study, the wollastonite concentrate which contains 0.44% Fe₂O₃, 52.71% SiO₂, 87.85% wollastonite with 0.60% loss on ignition (using 1500 g/t potassium oleate) was obtained. The ultimate grade concentrates of calcite that can also be obtained as by-products are with 99.80% calcite content and 85.4% recovery.