To polish diamonds they make use of the powder of adamantine spar, or the corundum stone.
Pliny says, corundum was used in the form of a splinter fixed in an iron style.
The stones have been rubbed into shape apparently by corundum.
The color of corundum is usually brown, but it varies greatly.
There are indications of sapphires and other forms of corundum.
Corundum ...
