... silica stone, good hardness and purity, widely used for glass industry, ceramic, foundry,metallurgy. IntroductionSilica sandA kind of ... 5ppm30-60mesh 99.95% 30ppm 40ppm 5ppmSilica sand for optical glass: for its high purity;Refined silica sand: processed ... from natural silica stone, for tis high content;Application:Optical glass industry;Refractory material;Metallurgy, ceramic, foundry and abrasives; ...