Glass (sp.gr. 2.2 to 3.0)
The first of the “engineered” class of grinding media, glass beads (small balls) and balls were developed specifically for grinding applications where sand wasn’t available. Glass is manufactured in various grades (Lead-free Soda Lime, borosilicate, low alkali, black glass, and others) in sizes from 1 micron to 2 inches.
Good wear properties coupled with reasonable roundness means this is the best material to start with when conducting grinding trials. Low cost.
Glass balls are also available in precision grades and are used in optical resolution systems and as “spacers” for precision electronics. Colored glass balls are used for both engineering and decorative applications.