Rough DIAMOND, is the stone as nature produces it in the mines.
A rough diamond must be chosen uniform, of a good shape, transparent, not quite white, and free of flaws and shivers. Black, rugged, dirty, flawey, veiny stones, and all such as are not fit for cutting, they use to pound in a steel mortar made for that purpose; and when pulverized, they serve to saw, cut, and polish the rest. Shivers are occasioned in diamonds by this. That the miners, to get them more easily out of the vein, which winds between two rocks, break the rocks with huge iron levers, which shakes, and fills the stones with cracks and shivers. The ancients had two mistaken notions with regard to the diamond: the first, That it became soft, by steeping it in hot goats blood; and the second, that it is malleable, and bears the hammer. Experience shows us the contrary; there being nothing capable of mollifying the hardness of this stone; though its hardness be not such, that it will endure being struck at pleasure with the hammer.