Borite

From Memory Alpha, the free Star Trek reference

Borite was a mineral found on some Federation planets.

Its uses and properties were unknown. Federation criminals were sometimes sentenced to mining borite for the rest of their lives.

Leonard McCoy was worried that he, and the rest of his party, would be court-martialed and sentenced to mining borite after the Genesis incident when they would return to Earth. (Star Trek IV: The Voyage Home).