“Bort” refers to shards of small, impure diamonds, or the small fragments removed from gem-quality diamonds during the cutting process. It is also a term used to describe low-grade diamonds, not of gem quality. Both categories of bort are utilized mainly in a variety of abrasives. The origin of the word “bort” is not entirely known, but is speculated to have come from the Old French “bord” or “bort,” meaning “bastard.”
Carbonado or “black diamond” is a dark-colored, impure diamond with a slightly different and more rare structural form and chemical composition. It is composed of crystalline diamond, graphite, and amorphous carbon; it is the hardest form of natural diamond. Like bort, it is mainly used as an abrasive and for diamond set drills.
Though bort and carbonado are certainly less glamorous than the gem-quality diamonds, they are by far the more abundant and useful. About 80% of all diamonds mined (representing around 130,000,000 carats or 26,000 kg per year) are industrial-grade. With the highest hardness, thermal conductivity and melting point of any mineral, these humble-looking diamonds possess the properties which rank them among the most useful industrial materials in the world.
Featured photo: Bort as a combination of shards and crystals. Photo courtesy of Wikimedia Commons.