The Lucara Diamond Company has announced discovering what is believed to be the third largest diamond ever found at its Karowe Mine in eastern Botswana, in a press release issued on 21 August 2024. The diamond weights 2492 carats (498.4 grams), making it larger than the previous third largest diamond ever discovered, the 1758 carat Sewelô Diamond, which was discovered at the Karowe Mine in 2019.
The new, and as yet unnamed, diamond revealed by Lucara Mining thing month. Lucata Mining.
The largest diamond ever found is the Sergio Diamond, found at Lençóis in Bahia State Brazil, in 1895, by Sérgio Borges de Carvalho, after whom it is named, which weighed 3167 carat (633.4 g). Surprisingly, the Sergio Diamond was not found within a diamond mine, but on the surface. The Sergio Diamond was a carbonado, a type of diamond with a black colour, a micro-porous structure, and a high graphite and amorphous carbon content, as well as frequently containing inclusions of other minerals or metals. Notably, some of the inclusions found in carbonado diamonds are extremely rare on Earth, and they have very low proportions of the isotope carbon¹³ compared to other diamonds, as well as radioactive inclusions, again not found in other diamonds. All caronado diamonds subjected to uranium-lead isotope dating have been found to be about 3 billion years old, and almost all carbonado diamonds come from two locations, Brazil and the Central African Republic. This has led to speculation that these diamonds are derived from an extra-terrestrial body which impacted the Earth in the distant past, although no hypothesis as to how such a body could have formed has ever gained widespread acceptance. Because of their hardness, carbonado diamonds were widely sought for use in drill bits in the nineteenth century, although they have been replaced by more modern materials today. Despite its exceptional size (most carbonado diamonds are smaller than a pea), the Sergio Diamond was sold for £6400 in London in September 1895, then broken up to make diamond drill bits.
An engraving of the Sergio Diamond published in Popular Science Monthly in 1906. Wikimedia Commons.
The second largest diamond ever discovered, and the largest gemstone-quality diamond, was rhe Cullinan Diamond found at Cullinan in what is now Gauteng Province, South Africa, in April 1905, which weighed 3106 carat (621.2 g) when it was found. The Cullinan Diamond was purchased by Louis Botha, the Prime Minister of the Transvaal Colony, and given to the British King Edward VII, who had it cut into nine large gemstones and a number of smaller fragments known as 'The Brilliants'. The largest of these cut stones, known as Cullinan I or the Star of Africa, has a mass of 530.4 carat, and is mounted on the Sceptre with Cross, part of the British Crown Jewels, which is carried by the monarch at their coronation.
(Left) The uncut Cullinan Diamond in 1908. (Right) The Star of Africa Diamond in the Sceptre with Cross in 1919. Wikimedia Commons.
Six of the eight largest diamonds ever dug up have been discovered at the Karowe Mine since 2015; this is not a coincidence. but marks the introduction of new technology pioneered at the Karowe Mine. Modern mines typically use crushing machinery to extract diamonds from their parent rock, but this is generally thought to break up a significant proportion of larger diamonds. The Karowe Mine uses X-ray fluorescence technology to scan ore before it passes into the crushing equipment, thus allowing for the machinery to be stopped and particularly large diamonds to be recovered.
Flow chart showing the processing and sorting of diamonds at the Karowe Mine. Lucara Diamonds.
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