Carbonado

Carbonado diamondites Bangui region, Central African Republic

Carbonado, commonly known as black diamond, is a natural polycrystalline form of diamond that is found primarily in alluvial deposits in the Central African Republic and Brazil. Its natural color ranges from black to dark grey, and it is more porous than other diamonds. Carbonado diamonds are notable for their extreme hardness and resistance to corrosion, making them highly valuable in industrial applications such as drilling and cutting tools. Unlike other diamonds, carbonados do not form in the Earth's mantle but are believed to have originated in space and arrived on Earth via an asteroid impact.

Formation and Characteristics

The exact origin of carbonado diamonds has been a subject of debate among scientists. The prevailing theory suggests that carbonados were formed by supernovae explosions and arrived on Earth through asteroid impacts approximately 2.6 to 3.8 billion years ago. This theory is supported by the presence of isotopic anomalies in carbonados, indicating an extraterrestrial origin. Carbonados are composed of diamond, graphite, and amorphous carbon, with inclusions of other minerals that suggest formation under high-pressure conditions.

Carbonados exhibit a unique microstructure characterized by polycrystalline aggregates of diamond crystals, which gives them their dark color and exceptional hardness. They are the toughest form of natural diamond, making them highly resistant to fracture.

Geographical Distribution

The primary deposits of carbonado diamonds are found in the Central African Republic and Brazil, specifically in the states of Bahia and Minas Gerais. The distribution of carbonado deposits is unusual because they are found only in these specific alluvial deposits, which are not associated with kimberlite pipes that are typical sources of conventional diamonds. This unique distribution pattern further supports the theory of an extraterrestrial origin for carbonados.

Applications

Due to their extreme hardness and toughness, carbonados are primarily used in industrial applications. They are ideal for use in drilling bits and saw blades where conventional diamonds would quickly wear out or fracture. Carbonados are also used in the production of deep-sea drilling equipment and in the manufacturing of specialized cutting and grinding tools.

Value and Rarity

Carbonado diamonds are valuable both for their industrial applications and as gemstones. Although they are not typically used in jewelry due to their dark color, carbonados have gained popularity in certain niche markets for their unique appearance and the mystique surrounding their origin. The rarity and unusual properties of carbonados make them highly sought after by collectors and researchers alike.

Research and Controversies

The origin of carbonado diamonds continues to be a subject of research and debate. While the extraterrestrial origin theory is widely accepted, some scientists propose alternative explanations, such as formation in high-pressure, high-temperature conditions within the Earth's mantle, similar to other types of diamonds. Ongoing research aims to unravel the mysteries of carbonado formation, distribution, and properties.