Bi-Coloured Diamond

A Rare Bi-Coloured Diamond: The 37.41 Carat Discovery from Botswana

You might find it unusual that my first blog post is about a bi-coloured diamond. But in many ways, it represents the perfect place to begin.

A Life Spent Among Rough Diamonds

I started my journey in diamonds as a De Beers trainee in 2002. I was 21 years old. Before my apprenticeship, I had briefly studied rough diamonds while completing my DGA — the Diamond Diploma from the Gemological Association of Great Britain.

At the time I joined the company, annual rough diamond sales were in the region of $5–6 billion, depending on market conditions. It’s difficult to visualise what that looks like in physical terms, but imagine this: every month, multiple tables — each around sixty metres long — would be filled with millions of rough diamonds.

Annual production was around 40–50 million carats. Remarkably, that entire volume could fit into something the size of a small garden shed.

After completing my two-year apprenticeship, I began buying rough diamonds first in Russia, then Namibia, South Africa, Canada, and most importantly Botswana. Over the following decade, I spent my days examining, valuing, buying, sorting, mixing, and appreciating rough stones — from 8:30am to 5:00pm, for roughly 2,600 working days. That’s millions upon millions of diamonds.

Why a Bi-Coloured Diamond Is So Rare

At this point, you might wonder what any of this has to do with a 37.41 carat bi-coloured diamond discovered in Botswana.

Here is the connection.

During those years of examining vast quantities of stones, I would occasionally encounter something unusual — a diamond displaying two distinct colours. Most often, this would be a brown diamond where one side appeared clearly white and the other brown. On rarer occasions, I would see faint pink stones with some degree of colour zoning.

But what I almost never encountered were true bi-coloured pink diamonds — stones where two distinct colours exist in clear and natural separation. This is what makes this Botswana diamond so exceptional.

The Science Behind Pink Diamond Colour

Understanding why diamonds display colour is still an evolving area of gemological research. While it is widely accepted that pink diamond colour is linked to plastic deformation within the crystal structure, the precise atomic mechanisms responsible remain only partially understood.

For gemologists, stones like this are not only visually remarkable — they are scientifically important. Each example contributes to a deeper understanding of how colour forms in natural diamonds.

A 37.41 Carat Diamond from the Karowe Mine

The importance of this discovery is amplified by its size. At 37.41 carats, this bi-coloured diamond is extraordinary. For context, the GIA has previously examined comparable type Ia pink and colourless bi-coloured rough diamonds, reportedly from Australia’s Argyle mine (since closed). However, those specimens were significantly smaller, each weighing less than 2 carats.

This diamond, unearthed at the Karowe mine in Botswana, measures 24.3×16.0×14.5 mm. Examination shows a predominantly sharp boundary between the pink and colourless zones — a defining feature that further enhances its rarity.

Source: sewelomag.com

The Importance of Origin: Botswana Diamonds

Botswana has long been one of the world’s most important sources of natural diamonds, known not only for quality but also for responsible sourcing, ethical mining practices, transparency and the social economic benefit it has brought to the country and its remote communities.

Discoveries such as this reinforce Botswana’s position at the very top of the natural diamond world — where rarity, beauty, and origin come together.

A Final Thought on Rarity

After decades spent looking at millions of rough diamonds, it takes something truly exceptional to stand out. A bi-coloured pink diamond of this size and clarity is one of those rare moments, it is a reminder that, even after decades of discovery, nature still has the ability to surprise me.