they are effective in both wet and dry states, using continuous or intermittent mills. the sphericity, uniform sizing and low wear rates of our french pebbles, contribute to low-end product contamination and the most efficient grinding. hd alumina. hd alumina is an alternative high density media, with increased grinding efficiency and low media wear rates, again resulting in,grinding media atems,silica pebbles can be used as a grinding medium for ceramics ball mill. it is suitable for all kinds of ceramic raw materials. our high silica content flint pebbles are usually used in ceramic or insulator industries as grinding media. to mill or grind raw materials like sand, kaolin clay, feldspar and other materials in ball mill.