... : calcite, marble, limestone, kaoline, gesso, barite, coal ash and slag, etc.(2) Hard materials: carborundum, brown corundum, superfine ... cement, zirconium sand, and fire-proof materials, etc.(3) High purity materials: quartz, ... alumina, glass fine bead, etc.(4) Metal powders: zinc powder, aluminum powder, iron powder, and molybdenum powder, etc.