Hardness: because it is a destructive test, so the stone without grinding or not precious ores can be used. The hardness of the scale has two kinds, one kind is the absolute hardness, another kind is the Mohs hardness (a relative hardness).
Mohs hardness: with ten kinds of minerals common comes as standard with a mutual scraping to distinguish or hard or soft, mineralogy gemology habit or are using the Mohs hardness. Mohs hardness is divided into ten stages. Gypsum, talc, calcite, fluorite, apatite, orthoclase, quartz, topaz, corundum, diamond.
The goal is a general characterization of the pore size sieve size, the conversion formula: cm=16/ mesh; mesh with English and American, British refers to the amount of holes per square inch
Traditional Raymond mill the existence of these problems have been plaguing the mineral processing enterprises and equipment manufacturers. These problems are mainly manifested in: