The formula of Wollastonite is CaSiO3. The ideal chemical specifications are as followed: ???SSiO2 51.75% ???CaO 48.25% ???Heated-Swelling ???Coefficient:6.5?0-6??1 ???Moh? Hardness 4.5-5.0 ???Density 2.8 ???melting Point 1540??br />???Refraction Index 1.62 ???The actual chemical specifications ???are as followed: ???SiO2 ???41-53% ???CaO ??? 38-48% ???Fe2O3 ??1.0%max ???MgO ??? 2.0%max ???Al2O3??1%max ???S,P ??? 0.1%maz