How Blue Diamonds Are Formed: Secret Origins of Blue Diamonds

How rare blue diamonds form deep below the ocean floor - scientists have recently shed light on the special process

Blue diamonds are considered the rarest of the rare among gemstones, and the reasons for this have eluded scientists for centuries.  Recent scientific evidence has finally been able to explain how blue diamonds are created deep below the surface of the earth.

Watch this short video clip from the Associated Press to understand the secret origins of blue diamonds that are finally coming to surface.

Blue Diamonds - Argyle Diamond Investments
Understanding how blue diamonds are formed. Unfolding the secret origins of the deepest coloured diamonds ever found.

Image Credits: Argyle Diamond Investments Pty Ltd.

Scientists have discovered the secret origins deep, deep down and may have solved this centuries-long mystery. Video Credits: Evan M. Smith/ © 2018 GIA

The process of creating a blue diamond

Experts believe that their point of origin is more than 400 miles below the earth’s surface, making these the deepest originating coloured diamonds known.

They are thought to be funnelled up by volcanic eruptions, commonly through kimberlite pipes. These pipes are tunnels of rock pushed up to the surface from volcanic activity, and when they travel through a diamond deposit, they bring them to the surface as well.

According to the journal Nature, blue diamonds are formed in the lower mantle, at depths more than four times that of other gemstones.

Scientists also suggest that the material from which the blue diamonds formed contained water that came from the oceanic lithosphere (the tectonic plates beneath the sea) – which is a rich source of boron.

Findings show that blue diamonds are found at astonishing depths when compared to other types of diamonds.

How rare blue diamonds form deep below the ocean floor has revealed a geochemical cycle that extends from the oceanic lithosphere at the earth’s surface to the lower mantle.

Interestingly, the secret origins of blue diamonds show a potential route for the ultra-deep cycling of water in planet earth.

How Blue Diamonds Are Formed: Secret Origins of Blue Diamonds - blue diamonds
Image Credits: Argyle Diamond Investments Pty Ltd.

The Rarest of the Rare

“Blue diamonds are among the rarest of the rare…because of that they are very highy priced, and  they’ve had an important place in history. Blue diamonds are among the deepest  diamonds that we’ve discovered.”

Steve Shirey, Carnegie Institute for Science

Where are natural blue diamonds found?

The Argyle Diamond Mine in the East Kimberly region, located in the remote north of Western Australia, is the world’s largest diamond producer by volume.

The mine provides a large proportion of naturally coloured diamonds, including the extremely rare blue diamonds.

Additionally, the mine produces over 90% of the world’s Pink Diamond supply. The Argyle Diamond Mine is one of the only known significant source of pink diamonds, as well as red diamonds. With the closure of the mine set for the year 2020, blue diamonds are about to get a whole lot rarer and will make an incredible investment.

To view or invest in rare blue diamonds or other coloured diamonds, contact the certified Australian diamond specialists.

The Argyle Diamond Mine sporadically yields blue diamonds – considered the rarest of all diamonds in the planet. A diamond is 25 times rarer than a pink diamond. This fact makes an Australian blue diamond a stand-out in investors’ collections.

Image Credits: Wikimedia Commons

How Blue Diamonds Are Formed: Secret Origins of Blue Diamonds - blue diamonds

How Blue Diamonds Get Their Colour

According to Evan Smith (E. M. Smith et al. Nature 560, 84–87; 2018), a scientist at the Gemmological Institute of America (GIA), the beautiful blue diamond contains trace quantities of the mineral boron.

For over two years, Smith and his team were able to study 46 blue diamonds that passed through the gemmological institute, all of which harboured minerals that are only found in the earth’s mantle.

Smith’s team have provided an answer to the geochemical conundrum: “blue diamonds are formed in the earth’s mantle, whereas boron is concentrated in the earth’s crust. So where did blue diamonds get their boron from?”

According to Smith et al. (2018) in the journal Nature,   

How Blue Diamonds Are Formed: Secret Origins of Blue Diamonds - blue diamonds

“Boron could have easily hitched a ride on sinking ocean tectonic plates all the way down to the lower mantle. That boron was inherited by these blue diamonds.”

– Evan Smith, Research Scientist at the Gemological Institute of America

The earth recycles rocks through the subduction process, where a tectonic plate slides beneath another, sinking into the mantle where it melts. This collision of tectonic plates causes earthquakes and sometimes tsunamis.

Boron is abundant in seawater. Smith states that hydrous minerals could be carrying stores of the blue-bearing element deep down where diamonds eventually capture it as they form. 

This cross-section from Evan Smith shows the hypotheses on how boron moved from the ocean floor (where it was bound to rocks chemically) to some660 kilometres down to the Earth’s lower mantle.

How Blue Diamonds Are Formed: Secret Origins of Blue Diamonds - blue diamonds

Image Credits: Evan Smith ©GIA

Other Sources of Blue Diamonds

There are other ways that diamonds can become blue, but they aren’t naturally formed that way. These include:

Diamond enhancement – Natural diamonds that have undergone enhancements to produce blue coloured diamonds, including HPHT (high pressure, high temperature).

Synthetic diamondsLaboratory-grown diamonds (LGD) – these blue diamonds have been manufactured by people.

Coloured or blue diamonds that come from both these sources are not rare. Their value is only a minimal percentage of the price paid for natural diamonds with a natural blue colour.

Trade Commissions have updated their rules and guidelines to protect consumers from fraudulent diamond investments. Consumers should likewise practice caution and discernment when evaluating or shopping for natural blue diamonds.  

How Diamonds Form - Other Theories and Myths

There are a number of persistent myths and theories surrounding the formation of diamond, and these include:

Diamonds from the metamorphism of coal – this hypothesis continues to be the story told in many science classrooms. But very rarely (if at all), has coal been shown to play a role in diamond formation. In fact, according to com, diamonds that have been dated are much older than earth’s first land plants, which is the source material of coal.

Meteor or asteroid impact sites – rare diamonds have been found in and encircling the craters of several planetary body impact sites, such as the famous Popigai Crater in northern Siberia, Russia. Throughout history, earth has been repeatedly hit by cosmic bodies such as asteroids. This is thought to be another method of how diamonds form.

These planetary bodies have hit the earth with such massive force that temperatures and pressures high enough to form diamonds have resulted. It has been shown that if the target rock contains carbon, the conditions required to create diamonds might have occurred within the impact site.

These types of diamonds are likewise considered rare, especially if impurities have found their way inside the diamonds. Different impurities give them their unique colours, sizes, textures and shapes.

Diamonds from ocean sediments subduction zones occur at convergent plate boundaries where one tectonic plate is forced down to the mantle. As this plate descends, it is exposed to increasing pressure and temperature.

Coloured diamonds – These have been discovered in rocks that are thought to have sub ducted, and then returned to the earth’s surface. These types of rocks are very rare. The diamonds found in these deposits are frequently very small for commercial use.

How Blue Diamonds Are Formed: Secret Origins of Blue Diamonds - blue diamonds

Image Credits: The Siberian Times

Diamonds from deep-source volcanic eruptions – most blue diamond deposits (as in the hypothesis of Smith and team) are believed to have formed from deep-seated volcanic eruptions. 

These volcanic eruptions are thought to be violent and occurred a long time ago in earth’s history. These were probably at a time when the earth was hotter, which could explain why the eruptions were very deeply rooted. 

The eruptions are believed to have carried the already-formed diamonds from the upper mantle to the surface of the earth. When the explosion reached the surface, it built a mound of volcanic material that contained diamonds within. These are the so-called Kimberlites that are typically the sources of many of the world’s mined and coloured diamonds.

The final word on blue diamonds

Natural blue diamonds, however they were formed, may be considered windows to the heart of the earth. A number of them have inclusions (or impurities) that contain evidence of activities in the heart of our planet.

Its “crystal cage” structure, has in many cases prevented the escape of materials in scenarios the gemstone has experienced in the past, in a similar way to specimens captured in amber. For that reason, what jewellers might see as flaws, scientists find priceless. One thing is for sure – these highly-priced gems continue to play an important place in history.

For enquiries about blue diamonds for investment purposes or for extremely fine jewellery, Argyle Diamond Investments Pty Ltd are the best specialists to help you find the right diamond. With many years of diamond specialisation and a particular focus on diamonds as investment options, we have the knowledge to help you navigate the niche world of investment diamonds. Contact our friendly team today, and get the facts from the experts!

Argyle Diamond Investments Pty Ltd are Australia’s largest supplier of Australian certified pink diamonds and have exclusive use of the Australian Pink Diamond Analytics program. This program is a data driven decision maker that tracks and statistically analyses the rarity, financial growth and value of all investment grade pink and blue diamonds. With this valuable information, Argyle Diamond Investments Pty Ltd can offer all clients an investment grade pink from $5,000AUD up. But, the highest growth diamonds, are the larger, stronger colour pinks starting from around $20,000AUD plus.


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