I don't know. Mine was bought almost 70 years ago. I just can't throw anything out. d8-)
"Bort" (also spelled "boort") is trade jargon for what most people call industrial diamonds. But there are synthetic diamonds in several forms today, used in industry, and calling them "industrial diamonds" can lead to some confusion.
Depending on what you want it for, synthetics may be a better choice. Google around on "industrial diamonds" and you'll find out all about them, including both the natural bort and synthetics.
Huh. I didn't realize they cracked carbide that way.
-- Ed Huntress