Sifting segregation is by no means the only mechanism to cause separation of particulate material during handling some particles have differences in inter-particle friction and thus form piles with different repose angles formation of piles within process equipment causes the less frictional particle to slide further down the pile accumulation at the pile edge this mechanism results in a radial segregation pattern material with an angle of repose difference of more than 2 degrees can show significant repose angle segregation the figure below illustrates segregation of fine and coarse fractions of roofing granules due to angle of repose in this case the particles size difference between the fines and coarse is only about 30% so sifting is not possible the repose angle are only 2 degrees difference and are the case of significant segregation