• Mohs scale
• Industrial applications of abrasives

Abrasives are materials used to wear down, smooth, clean, shape, or polish a surface. The perfectly smooth surfaces needed in telescope mirrors, for example, are produced by grinding a piece of glass or metal with abrasives. One of the most familiar abrasives is sandpaper, heavy paper coated with a thin layer of aluminum oxide or silicon carbide. Sandpaper can be made in many grades, from coarse to very fine. The grade of sandpaper depends on the size of abrasive particles it contains.

Abrasives can be either natural or synthetic materials. Until the twentieth century, humans used naturally occurring materials, such as sandstone, quartz, emery, corundum, diamonds, and garnet, as abrasives. Then, in 1891, American inventor Edward G. Acheson (1856–1931) produced silicon carbide by...