Boart
Bort
Shards of non-gem-quality diamonds
Bort, boart, or boort is an umbrella term used in the diamond industry to refer to shards of non-gem-grade/quality diamonds. In the manufacturing and heavy industries, "bort" is used to describe dark, imperfectly formed or crystallized diamonds of varying levels of opacity. The lowest grade, "crushing bort", is crushed by steel mortars and used to make industrial-grade abrasive grits. Small bort crystals are used in drill bits. The Democratic Republic of the Congo provides 75% of the world supply of crushing bort.[1][2][3]