Preferred grinding media are {HEAD ~ spherical ceramic particles} having a smooth and substantially uniform exterior surface, {TAIL ~ a high density} and high hardness 
having
Preferred grinding media are { HEAD ~ spherical ceramic particles } having a smooth and substantially uniform exterior surface , { TAIL ~ a high density } and high hardness
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH