... of harmful and on the environment have serious pollution of silica dust, dust once inhaled, can easily cause silicosis or even ... minerals, and inside do not contain cause silicosis of free silica hazardous substances, heavy metals are not toxic or radioactive contaminants ... .49-8.00 and specifications :8-220 project. Chemical composition; SiO2 35-40%, Al2O3 18-20%, FeO 25-37%,Fe2O3 0 ...