Carbonado
Carbonado, commonly known as black diamond, is one of the toughest forms of natural Diamond. It is an impure, high-density, micro-porous form of polycrystalline diamond consisting of diamond, graphite, and amorphous carbon, with minor crystalline precipitates filling pores and occasional reduced metal inclusions. It is found primarily in alluvial deposits where it is most prominent in mid-elevation equatorial regions such as central Africa and in Brazil, where the vast majority of carbonado diamondites have been found. Its natural colour is black or dark grey, and it is more porous than other diamonds.