It is needed to be noticed that an ore is usually composed of several minerals which have different physical properties and sometimes those are differences are big. When this type of ores is crushed, the minerals in it are crushed differently. Some of them are crushed to thick particles while the others are crushed to fine ones. And the phenomenon is called selective crush. The key reason for the occurrence of selective crush is that the mechanical property in each mineral is big and the property of crushing machine also has influence on it. For example, Impact Crusher and autogenous mill are easy to create selective crush. And it should be noticed that it is important in mineral separation. For example, toward those ores whose useful minerals are easier to be mud than gangues, their granularities which possess useful disintegrated minerals should be distinguished without waiting for the whole ores are grinded to the same granularity for it is good for reducing overcrushing.

 

After understood the mechanical property of the ores and force application situation of crushing equipments, it should be considered that the force application method of crusher should fit the property of the ores and then there will be good crushing effect. Toward the hard ores, crush them by adopting bending and impact for grinding and stripping will damage the equipment seriously. Toward those fragile ores, bending and splitting is better. If choose grinding and stripping, there will be too much extra-fine powder. Toward those tough or extra-tough ores, it is reasonable to adopt grinding and stripping crush. For the dynam property of the materials is different, the crushing equipments for them are various.