Coal is light, and its density is far below other type of rock, only 1.5-1.7 grams/square centimeters. the raw coal dug from coal mine has relatively smooth surface, which will cause a phenomenon that some coals cant be broken when jaw board squeezes. therefore, the production is often low if use jaw crusher machine as coal crusher.Crushers. stone crusher. jaw crusher; … reliable performance to the foreign advanced level of coal flotation machine for non … coal inflatable flotation device: … * hot sale ball crusher device with iso in chromium.