Carborundum

[Sarah]

A beautiful crystalline compound, SiC, consisting of carbon andsilicon in combination; carbon silicide. It is made by heating carbonand sand together in an electric furnace. The commercial article isdark-colored and iridescent. It is harder than Emery, and is used asan abrasive.

[Gregory]

a compound of silicon and carbon that is used as an abrasive (= a substance for rubbing away surfaces)