... yellow, chemical fertilizer, compound fertilizer, fly ash, bituminous coal, coking coal, lignite, magnesite sand, chrome oxide green, gold, red ... mud, clay, kaolin, coke, coal gangue, porcelain clay, kyanite, fluorspar, bentonite, rhyolite, pyrophyllite, ... , silicon carbide, thermal insulation materials and other non-flammable burst materials whose Mohs hardness are below 9 ...