Diamonds are mined every other day, but it is not every day that a large diamond is unearthed, and, up until 10 years ago, super-large diamonds were a rarity. Today, the discovery and unearthing of the 2,492-carat raw diamond from the Karowe mine in Botswana, by Canadian mining company Lucara Diamond Corp, is turning that previously-held belief on its head, especially as it is one of several large diamonds mined in Africa in recent years.
How was it discovered?
Per the mining company, this remarkable discovery was made possible by its Mega Diamond Recovery X-ray Transmission technology, which it adopted in 2017. “The ability to recover such a massive, high-quality stone intact demonstrates the effectiveness of our approach to diamond recovery,” says William Lamb, President and CEO of Lucara.
But it isn’t the first large diamond to be discovered in recent years
Significant as this discovery is, large and super-large diamonds are becoming more common than they were 20 years ago. Lucara alone has unearthed other sizable diamonds in the past from the Karowe mine, including the 1,109-carat Lesedi La Rona diamond in 2015, and the 1,174.76-carat stone in 2021. There is also the impressive 1,758-carat Sewelô find excavated in 2019 and sold to Louis Vuitton in 2020.
The Letšeng mine in Lesotho has also produced significantly large diamonds in recent years. In 2019, its London-based owner, Gem Diamonds Ltd, announced the discovery of a 910-carat diamond from the mine. Since then, it has yielded more big stones weighing 603 and 530 carats, along with four others weighing 300 carats or more.
Why were large diamonds not more common before now?
The largest gem-quality diamond ever discovered was the 3,106-carat Cullinan diamond from a South African mine in 1905. It was cut into nine major stones — the 530-carat Star of Africa, the 317-carat Second Star of Africa, and seven other large gems — and 96 “minor brilliants.”
Since then, it has been nearly impossible to get large diamonds from mining operations, leading excavators to believe that big natural diamonds are a rarity.
Newer technologies have however helped to debunk this fact.
Typically, the grade of an ore determines the size of a diamond, and higher-grade ores – kimberlite ores containing 1 carat of diamond per ton are considered high–grade –yield smaller diamonds, and vice versa.
However, the process of drilling for these precious stones seems to be the bigger culprit behind the limited discovery of large diamonds in the past.
Most of the mines in southern Africa are huge, mechanized open pits, where ore is drilled, blasted, crushed to 6 inches in size, and fine-crushed to 1 inch, whereupon diamonds are ‘lighted-up’ using X-ray beams and separated from crushed ore with the help of light-sensitive separating devices.
This process may have caused the loss of large diamonds over the years in African mines that have proven to be sources of big stones. It is why mines are incorporating newer X-ray technologies that scan kimberlite ore before the first crushing step. Since X-rays can reveal density differentials, they may indicate the presence of large diamonds even if these are completely hidden within chunks of kimberlite.
What does this mean for the precious stone mining industry?
For now, it is hard to say. However, large diamonds could mean that more jewellery pieces can be made from just a single discovery, reducing the need to constantly mine for stones to meet up with demand.
Lab-grown diamonds can eliminate the need for constant mining, but, for now, there is a huge market for natural diamonds, and, trying to preserve nature while still meeting this demand is top priority for businesses in this niche. Large diamonds such as this 2,492-carat from the Karowe mine may just be the solution that has been hiding in plain sight all along.