PC010021DIAMONDS.NATIVE ELEMENTS C(Carbon)System Isometric.Appearance Usually octahedral,rounded crystals. Colorless,yellow,brown,gray,green , black and pink. Blackish microcrystalline masses,radiate structure (bort variety) Physical properties Dimorphic with graphite.The hardest-mineral (10 on the Mohs scale). Heavy,fragile,with perfect cleavage.Transparent with adamantine luster and strong dispersion of light. Insoluble and infusible.Burns with difficulty,giving off carbon dioxide.Often fluorescent in ultraviolet light.