noun
black diamond; carbonado
Refers to the opaque, polycrystalline diamond variety known as carbonado, used industrially or as a gemstone.
黒金剛石は工業用の研磨材として使われることがある。
Black diamonds are sometimes used as industrial abrasives.
Compound of 黒 (kuro, 'black') + 金剛石 (kongōseki, 'diamond'). The exact historical derivation is uncertain; the term directly describes the black variety of diamond.