Bort or boart is a term used in the diamond

Diamond

In mineralogy, diamond is an allotrope of carbon, where the carbon atoms are arranged in a variation of the face-centered cubic crystal structure called a diamond lattice. Diamond is less stable than graphite, but the conversion rate from diamond to graphite is negligible at ambient conditions...

 industry to refer to shards of gem

Gemstone

A gemstone or gem is a piece of mineral, which, in cut and polished form, is used to make jewelry or other adornments...

-grade/quality diamonds. In the manufacturing and heavy industries, "bort" is used to describe dark, imperfectly formed/crystallized diamonds of varying levels of opacity. The lowest grade, "crushing bort", is crushed by steel mortar

Mortar and pestle

A mortar and pestle is a tool used to crush, grind, and mix solid substances . The pestle is a heavy bat-shaped object, the end of which is used for crushing and grinding. The mortar is a bowl, typically made of hard wood, ceramic or stone...

s and used to make industrial-grade abrasive

Abrasive

An abrasive is a material, often a mineral, that is used to shape or finish a workpiece through rubbing which leads to part of the workpiece being worn away...

 grits. Small bort crystals are used in drill bit

Drill bit

Drill bits are cutting tools used to create cylindrical holes. Bits are held in a tool called a drill, which rotates them and provides torque and axial force to create the hole. Specialized bits are also available for non-cylindrical-shaped holes....

s. The Democratic Republic of the Congo

Democratic Republic of the Congo

The Democratic Republic of the Congo is a state located in Central Africa. It is the second largest country in Africa by area and the eleventh largest in the world...

provides 75% of the world supply of crushing bort.