| Carbonado | |
|---|---|
 Three carbonados from the Central African Republic | |
| General | |
| Category | Native minerals |
| Formula (repeating unit) | C |
| Crystal system | Isometric-hexoctahedral (cubic) |
| Identification | |
| Formula mass | 12.01 u |
| Color | Typically black, can be grey, various shades of green and brown sometimes mottled. |
| Crystal habit | Polycrystalline |
| Fracture | Irregular torn surfaces |
| Mohs scale hardness | 10 |
| Luster | Adamantine |
| Streak | White |
| Specific gravity | 3.52±0.01 |
| Density | 3.5–3.53 g/cm3 |
| Polish luster | Adamantine |
| Optical properties | None |
| Birefringence | None |
| Pleochroism | None |
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.[1] Titanium nitride (TiN, osbornite) has been found in carbonado.[2] It is found primarily in alluvial deposits where it is most prominent in mid-elevation equatorial regions such as Central African Republic 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.
- ^ Kroschwitz, Jacqueline I. (2004). Kirk-Othmer encyclopedia of chemical technology (5th ed.). Hoboken, N. J.: J. Wiley. p. 10. ISBN 9780471484943.
- ^ G. Parthasarathy; et al. (Aug 2016). "Osbornite (TiN): Implications for an extraterrestrial origin of carbonado- diamonds". 35th International Geological CongressAt: Cape Town, South Africa.