Origin Theories of Beautiful Black Diamonds

Origin of Black Diamonds Carbonados | Cape Town Diamond Museum

A Collection of Black Diamond Shapes

The origin of natural black diamonds has long been a geological puzzle and has baffled scientists for decades, because they appear to follow none of the rules of diamond mineralogy. While there are a few theories on where they come from, the actual formation of black diamonds remains a mystery, as science has yet to prove any of these theories. The birth of these beautiful black diamonds’ ranges from natural radiation to asteroid impacts and exploding stars. Let’s take a look at some of the most popular and intriguing theories of where black diamonds come from, and then be sure to book your tour of the Cape Town Diamond Museum to learn more about these fascinating gemstones.

Early Discovery

Origin of Black Diamonds Carbonados | Cape Town Diamond Museum

Earth and Moon being hit by speeding rocks

Also known as carbonados, black diamonds are believed to be very old with recent atomic measurements placing their genesis at around four billion years ago, a time when the Earth and Moon were hit by speeding rocks from space.

Black diamond deposits are incredibly rare and are usually mined from stream beds, with geologists not knowing exactly which bedrock they eroded from or when.

First recognised in 1840 in Brazil, carbonadoes received their name from the Portuguese term for burned or carbonized. From around 1925, black diamonds were gathered in the Central African Republic.

Theory #1: High-Pressure Conversion of Carbon Within the Earth’s Interior

Origin of Black Diamonds Carbonados | Cape Town Diamond Museum

Black Diamonds Are Not Formed Deep Within The Earth Surface

At first, scientists believed that black diamonds were formed in the same way regular diamonds are created: deep in the Earth’s crust at intense pressure and temperatures before being carried to the surface later by volcanic eruptions.

While the majority of diamonds are encased in rocks with characteristic minerals, this doesn’t seem to be the case with black diamonds. They’re not found in mantle rocks and tend to include metals in their structure that wouldn’t make sense if they formed in the mantle.

It wasn’t until the 1960s that this theory was discredited as scientists studied the mineral inclusions and carbon isotopes of black diamonds.

Theory #2: Meteoric Impact Theory (1985)

Origin of Black Diamonds Carbonados | Cape Town Diamond Museum

Meteoric Impact Formed Black Diamonds

In 1980, Luis W. Alvarez proposed that a killer rock from space had hit Earth 65 million years ago, creating a pall of dust that blocked sunlight, disrupted climate and was the cause for dinosaurs’ extinction.

In 1985, and in light of this new theory, Dr. Joseph V. Smith and Dr. J. Barry Dawson proposed that carbonados were formed from carbon-rich materials by large impacts on Earth’s crust.

During this time, other scientists noted that Africa and South America had been joined ages ago, before being cut in two by continental drift, and that a single collision might account for the carbonados of both Brazil and the Central African Republic.

Scientists around the world began to show that craters from cosmic impacts were often filled with trillions of translucent diamonds, believed to have made by the great heat and pressure of impact. However, most of these diamonds were very small and nothing as big as a carbonado was found in or around the impact craters that were known.

Theory # 3: Radiation (1991)

Origin of Black Diamonds Carbonados | Cape Town Diamond Museum

Black Diamonds Created From Earths Natural Radiation

Some scientists believe that black diamonds were created from natural Earth radiation, which was stronger billions of years ago. This theory was dealt a blow when Dr. Tyrone L. Daulton and Dr. Minoru Ozima of Washington University in St. Louis reported finding microscopic diamonds in uranium-rich carbonaceous rocks dating from Precambrian times and calculated that radiation alone would be insufficient to produce the big black diamonds that have been discovered.

Theory #4: Subduction Zone (1997 / 2004)

Origin of Black Diamonds Carbonados | Cape Town Diamond Museum

Tectonic Plates Colliding

The subduction zone is boundaries where tectonic plates collide and get shoved down into the mantle. The pressure and heat of this process would be more than enough, but we should find mantle minerals alongside black diamonds, making this theory not very plausible.

Theory #5: Extra-terrestrial (1996)

Origin of Black Diamonds Carbonados | Cape Town Diamond Museum

Carbonados Come From Interstellar Space

All of the above theories lead scientists to suspect that carbonados must come from interstellar space. The crystals could form out there in a distant carbon-rich spot, and then get deposited here on Earth via an asteroid. This space theory could also account for the mysterious metal inclusions.

Another point to consider is that black diamonds are only found in Brazil and the Central African Republic, which could be explained by an intense barrage of space rocks back when Africa and South America were part of the same supercontinent.

The Dr. Haggerty Theory proposes that Black Diamonds were born in dying stars and later fell to earth. Dr. Haggerty referred to them as ‘Boulders of Star Dust’. He conceded that this theory might only be proved by future space explorers who hunt for huge diamonds speeding through the solar system.

So, where do you think black diamonds come from? Visit the Cape Town Diamond Museum to learn more about the fascinating world of diamonds. Book your tour today. Located at the V&A Waterfront Clock Tower precinct. Open 9am to 9pm daily.