The mining and mineral processing industry uses screening for a variety of processing applications.  For example, after mining the minerals, the material is transported to a primary crusher.  Before crushing large boulder are scalped on a shaker with  thick shielding screening.  Further down stream after crushing the material can pass through screens with openings or slots that continue to become smaller.  Finally, screening is used to make a final separation to produce saleable products based on a grade or a size range.