Black Diamonds

Black diamonds owe their colour not to a body-colour absorption mechanism but to dense clouds of dark inclusions — graphite, hematite and magnetite — packed so thickly through the crystal that it reads as opaque black rather than a transparent hue. Natural Fancy black diamonds are judged on the evenness and depth of that colour and on polish, since the very inclusions that create the colour make the rough difficult to cut. A GIA coloured-diamond report separates natural black from the far more common irradiated or heat-treated material, and that natural-origin determination is the decisive value factor.