Raw Carbonado Diamonds

The origin of the carbonado diamond, often called the "black diamond," remains one of the most significant and unresolved mysteries in geology. Unlike typical diamonds which are formed deep within the Earth's mantle and brought to the surface by kimberlite eruptions, carbonados are found only in alluvial deposits in Brazil and the Central African Republic and exhibit unique characteristics that point to a radically different formation process.

The prevailing scientific debate centers on two main groups of theories: Terrestrial (Earth-based) origins and Extraterrestrial (Space-based) origins.

The Extraterrestrial Origin Theory (Leading Hypothesis)

The most widely supported and compelling theory posits that carbonados have an interstellar origin. This hypothesis is supported by several unique characteristics of the stone that are incompatible with Earth's mantle conditions:

1. Unique Inclusions: Carbonados contain trace elements like nitrogen and hydrogen, as well as highly reduced minerals like osbornite (titanium nitride). The presence of hydrogen suggests formation in a hydrogen-rich environment, which is characteristic of interstellar space rather than the Earth's mantle.

2. Lack of Mantle Minerals: Unlike normal diamonds, carbonados contain no inclusions of mantle minerals (like olivine or garnet), which should be present if they formed deep within the Earth.

3. Supernova Birth: The theory suggests carbonados were formed in the shockwaves of a supernova—the explosion of a giant, carbon-rich star—at least 3.8 billion years ago. This immense force and energy could have created the polycrystalline structure.

4. Asteroid Delivery: The diamonds likely coalesced in space, eventually forming large, asteroid-sized bodies that then fell to Earth as meteorites roughly 2.3 billion years ago. Their current deposits in Brazil and the Central African Republic are thought to be remnants of a single, massive impact event that occurred when the two continents were joined as part of the ancient supercontinent.

Competing Terrestrial Theories

While the extraterrestrial model is strong, other Earth-based mechanisms have been proposed to explain the diamond's unique structure:

1. Meteoric Impact Theory

This theory suggests that the diamonds were formed by the shock and intense heat generated when a large carbon-rich meteorite impacted the Earth's crust. The impact would have instantly converted organic carbon material at the site into diamonds. However, this is challenged by the fact that diamonds found at known impact sites are usually microdiamonds (much smaller) and do not have the same porous structure as carbonados.

2. Deep Crust/Subduction Zone Theory

This is a more modern hypothesis suggesting carbonados could have formed in the Earth's deep crust within subduction zones (where one tectonic plate slides under another). Organic carbon from ocean floor sediments is carried deep down, and the high pressure and heat of subduction could potentially create the polycrystalline structure. This theory, however, still struggles to explain the lack of mantle inclusions and the extreme reducing conditions necessary for certain minerals found within the carbonados.

In summary, the consensus among many leading geologists is that carbonado diamonds are truly fragments of an exploding star that arrived on Earth via meteorite impacts . This makes them one of the oldest and most exotic materials ever found on our planet.