Deep within the Earth’s mantle, under extreme conditions of heat and pressure spanning billions of years, nature crafted one the most dazzling treasures known to man: diamond. Among them, a rare few stand out, not just for their sparkle, but for their colossal size.
From the legendary mines of South Africa to the rich kimberlite pipes of Botswana, the world’s biggest rough diamonds continues to evolve. New discoveries are still shaking up the modern diamond industry, proving that we’ve still only scratched the surface of the sparkling world of diamonds.
10 Largest Diamond Discoveries:
1. The Sergio Carbonado: 3,167ct
Rough Weight: 3,167 carats
Mined: Found above ground, Bahia
Discovery: 1895, Lençóis, Brazil
The Sergio is the largest rough diamond ever found, but its not your typical gemstone. This black diamond, technically classified as a carbonado, was found above ground in the Brazilian state of Bahia in 1895 by Sérgio Borges de Carvalho.
Meteoric Origin
What makes this discovery particularly fascinating is that carbonados like the Sergio are believed to be of meteoric origin, suggesting this massive stone may have travelled through space before finding its home on Earth.
However, not meeting gem-quality standards for color, clarity, size, and shape, the Sergio Carbonado was was classified as an industrial diamond and ultimately broken into smaller pieces for industrial use. The Sergio sold initially for $16,000 and later for $25,000 before being shipped to Paris and eventually London. The stone was then fragmented into 3-6 carat pieces for use as diamond drills.
2. The Cullinan Diamond: 3,106ct
Rough Weight: 3,106 carats
Mined: Premier Mine, South Africa
Discovery: January 26, 1905
Discovered in 1905, the Cullinan Diamond is the largest gem-quality rough diamond ever discovered, weighing an astounding 3,106 carats when unearthed at the Premier No. 2 mine in South Africa.Named after Thomas Cullinan, the mine owner, the rough colourless stone measured 10.1 x 6.35 x 5.9 centimeters and boasted exceptional blue-white colour and clarity.
After remaining unsold for two years despite considerable interest, the Transvaal government purchased the stone for £150,000 and presented it to King Edward VII on his 66th birthday in 1907. The King accepted the gift “for myself and my successors,” ensuring its preservation among the historic jewels which form the “Heirlooms of the British Crown”.
The Largest Gem-Quality Diamond
Joseph Asscher & Co. of Amsterdam undertook the monumental task of shaping the rough Cullinan stone, with the first cut made on February 10, 1908. The cutting and polishing process took eight months to complete, ultimately producing 105 stones: nine large stones totaling 1,055.89 carats, along with 96 brilliants and various small fragments.
The two largest stones, The Cullinan I (the Great Star of Africa at 530.2 carats) and The Cullinan II (the Second Star of Africa at 317 carats), became part of the British Crown Jewels, where they remain today.
3. The Motswedi Diamond: 2,492ct
Weight: 2,492 carats
Mined: Karowe Mine, Botswana
Discovery: August 2024
In a discovery that made headlines worldwide, miners at the Karowe mine in Botswana unearthed the largest diamond found in over a century. The 2,492-carat Motswedi, weighing approximately 1,000g, represents the second-largest diamond ever discovered and the largest since the Cullinan more than a century ago.
Botswana’s Record-Breaking Discovery
The Motswedi diamond, named after the Setswana word for the flow of underground water, emerged from the same prolific Karowe mine that has become legendary for producing exceptional, large diamonds. Naseem Lahri, Botswana managing director for Lucara Diamond Corp., described the discovery as “history in the making,” emphasizing its significance as “a product of Botswana”.
The diamond’s discovery highlights the continued potential of Botswana’s kimberlite pipes, formed when ancient volcanic eruptions brought diamond-bearing rock from depths of 93 to 280 miles underground to the surface
While the diamond’s exact value remains undetermined, experts suggest it could be worth tens of millions of dollars. Like many large rough diamonds, the Motswedi will likely be cut into smaller stones, maximizing both its beauty and commercial value.
4. The Sewelô Diamond: 1,758ct
Rough Weight: 1,758 carats
Mined: Karowe Mine, Botswana
Discovery: April 2019
The Sewelô diamond, whose name means “rare find” in Setswana, was discovered in Botswana’s Karowe mine in April 2019, claiming the title of fourth-largest rough diamond ever found. At the time of its discovery, it was the largest diamond in Botswana’s history, surpassing the previously record-holding Lesedi La Rona from the same mine.
This tennis ball-sized diamond, measuring 83mm x 62mm x 46mm and weighing 352 grams, captured international attention when luxury fashion house Louis Vuitton purchased it in 2020 for an undisclosed sum.
Louis Vuitton’s “Rare Find”
The acquisition marked Louis Vuitton’s bold entry into the high jewelry market, with the company retaining a 50% interest in the individual polished diamonds resulting from the cutting process.
The Sewelô presents unique challenges and opportunities for its cutters. The stone is covered in a thin layer of opaque black carbon, and its surface is pitted, making initial quality assessment difficult.
However, analysis revealed it to be “near-gem of variable quality, including domains of high-quality white gem”. Louis Vuitton, working with Antwerp-based HB Company, is employing artificial intelligence mapping methods to optimize the cutting design. Potential options include a 904-carat cushion cut, an 891-carat oval, or several smaller diamonds ranging between 100 and 300 carats.
5. The Lesedi La Rona: 1,111ct
Rough Weight: 1,111 carats
Mined: Karowe Mine, Botswana
Discovery: November 16, 2015
The Lesedi La Rona, meaning “Our Light” in Tswana, represents the fifth-largest diamond ever found and the third-largest of gem quality. What makes this discovery significant is that two additional large diamonds weighing, 813 and 374 carats, were discovered at the same mine just one day later.
Estimated to be over 2.5 billion years old, this colourless Type IIa Lesedi La Rona diamond was found in the South Lobe of the Karowe mine, approximately 200 meters below the surface. Although recovered using modern diamond sorting technology, the stone’s impressive dimensions of 65mm x 56mm x 40mm made it too large for the company’s scanners.
“Our Light” from Botswana
The diamond’s discovery triggered a naming competition open to all Botswana citizens, ultimately won by Thembani Moitlhobogi from Mmadikola, who received P25,000 for the winning entry: “Lesedi La Rona.”
British jeweller Graff, purchased the Lesedi La Rona for $53 million in 2017, cutting it into one magnificent emerald-cut diamond weighing 302.37 carats (the Graff Lesedi La Rona) and 66 smaller stones.
6. The Excelsior Diamond: 995.2ct
Weight: 995.2 carats
Mined: Jagersfontein Mine, South Africa
Discovery: June 30, 1893
For twelve years, the Excelsior Diamond held the title of the largest diamond in the world, until it was surpassed by the Cullinan in 1905. Discovered in 1893 by a worker shoveling gravel at the Jagersfontein Mine in South Africa, this remarkable blue-white tinted gem weighed 971 old carats (995.2 metric carats) and earned the name Excelsior, meaning “higher,” in homage to its distinctive, elongated loaf-like shape.
The uncut stone measured approximately 2.5 inches by 2 inches and was 1 inch thick, displaying a dazzling white hue with a subtle blue tint. However, like many diamonds from the Jagersfontein mine, it contained black carbon inclusions that affected its overall clarity and quality, and presented significant challenges for the cutting and polishing process. Its internal crystalline structure resembled a fractured icicle, beautiful yet flawed.
The Cutting Controversy
Finally, after the diamond sat in the vault waiting for a buyer for many years, the owners made the decision to cut the stone into several smaller stones, , ranging from 13 to 68 carats. This decision meant that the Excelsior would never be a single large spectacular faceted stone. While this may seem like a dramatic reduction from its original weight, the cutting process allowed the removal of inclusions and maximized the beauty of the resulting gems.
However, this controversial decision shocked the diamond world at the time. The De Beers syndicate’s manager called it “the greatest tragedy of modern times in the history of famous diamonds.” Many experts believe the stone could have yielded a single, spectacular gem had it been handled differently. Why that opportunity was missed remains a mystery, adding a layer of intrigue to the Excelsior’s legacy.
7. The Star of Sierra Leone: 968.9ct
Weight: 968.9 carats
Mined: Alluvial Mining, Koidu area, Sierra Leone
Discovery: February 14, 1972
Discovered on Valentine’s Day 1972 in the alluvial mines of Koidu, the Star of Sierra Leone remains one of the most extraordinary diamond finds in history. Weighing 968.9 carats, it is not only the largest alluvial diamond ever recovered, but also ranks among the world’s largest gem-quality stones.
Classified as a rare Type IIa diamond, a rare category that includes less than 1% of all diamonds, the Star of Sierra Leone created a sensation upon discovery. Acquired by famed jeweller Harry Winston for under $2.5 million. The cutting process proved challenging due to an internal flaw, requiring the stone to be re-cut after the initial emerald-shaped stone was completed.
The Star of Sierra Leone was eventually cut into 17 finished diamonds, 13 of which were graded as flawless, with the largest, a 53.96-carat pear-shaped gem, becoming the centerpiece of the elegant “Star of Sierra Leone” brooch.
8. The Incomparable Diamond: 890ct
Rough Weight: 890 carats
Mined: MIBA Mine near Mbuji-Mayi
Discovered: Democratic Republic of the Congo, 1984
The Incomparable Diamond owes its discovery to pure chance. In November 1984, a young girl playing in a rubble pile near the MIBA diamond mine in the Democratic Republic of the Congo stumbled upon an oddly-shaped stone. That stone would turn out to be the 890-carat Incomparable.
The incomparable is the the third largest diamond ever cut, after the Cullinan 1 and Golden Jubilee, and the largest internally flawless diamond ever graded by the GIA. But the gem isn’t just famous for its size and flawless (IF) clarity, but for its unusual triolette shape and fancy brownish-yellow colour, making it the largest faceted yellow diamond in the world.
The Golden Giant
After years of study and planning, the stone was cut into a singular 407.48-carat gem, now known as the Golden Giant, or simply The Incomparable Diamond. The finished stone is a rich, deep yellow-brown color and was cut into a shield-shaped “triolette” to maximize weight retention.
After years on display in various exhibitions, the diamond was set in an extravagant necklace that included nearly 91 colourless/white diamonds totaling over 200 carats. The Mouawad L’Incomparable Diamond Necklace, featuring this diamond, holds the record for the most valuable necklace in the world.
9. The Constellation: 813 ct
Rough Weight: 813 carats
Mined: Karowe Mine, Botswana
Discovered: November 2015
The Constellation Diamond was discovered at the Karowe mine in Botswana in November 2015 by Lucara Diamond. Today, it’s recognised as the sixth-largest gem-quality rough diamond ever. Recovered just days before the discovery of the Lesedi La Rona at the same mine, the Constellation Diamond is a 813-carat colorless Type IIa gem that reaffirmed the Karowe mine’s reputation as one of the richest sources of large diamonds in the world.
Highest Price Paid for a Rough Diamond
In May 2016, the Constellation set a new benchmark for the diamond industry, selling for a record-breaking $63.1 million to Dubai-based Nemesis International. At the time, it was the highest price ever paid for a rough diamond.
Lucara Diamonds partnered with HB Antwerp to cut the Constellation, and early projections suggested the potential for a single, D-color polished diamond of over 300 carats, putting it in direct competition with some of the world’s most famous cut gems.
10. The Koh-i-Noor Diamond: 793 ct
Rough Weight (historic): Estimated 793 carats
Mined: Golconda Mines, India
Discovery: Unknown (first recorded in 14th century)
Though its exact original weight remains disputed due to incomplete historical records, the Koh-i-Noor diamond (Persian for “Mountain of Light”) is widely considered as one of the largest rough diamonds ever discovered. Its early history is shrouded in legend, with claims tracing it back to ancient Indian texts and royal dynasties of the Mughal Empire.
Over centuries, the Koh-i-Noor passed through the hands of emperors, maharajas, and conquerors. It became a symbol of conquest and power, worn by Babur, Shah Jahan, and Ranjit Singh before it was acquired by the British East India Company in 1849, following the annexation of Punjab.
The Demand for Repatriation
Now weighing 105.6 carats after being recut in 1852 to enhance its brilliance, the Koh-i-Noor sits in the British Crown Jewels, mounted in Queen Elizabeth The Queen Mother’s crown. Its placement remains controversial, with demands for its repatriation voiced by India, Pakistan, Afghanistan, and Iran.
Africa’s Legacy of Large Diamonds
From the legendary diamond discoveries of South Africa to the emerging Karowe mine of Botswana, Africa has become synonymous with the world’s most extraordinary diamonds. These glittering gems are not just natural marvels, they’re deeply embedded in the story of Africa itself: a continent whose geological riches continue to shape global luxury, royalty, and science.
Over the last century and beyond, Africa has produced nearly all of the world’s largest and most valuable rough diamonds. The Cullinan, the Lesedi La Rona, the Sewelô, the Star of Sierra Leone, the Excelsior, and the Constellation are not isolated discoveries, but part of a broader, ongoing legacy of exceptional size, colour, and clarity that consistently sets the global benchmark for what a diamond can be.
And, recent major discoveries in Africa, including the 2,492 carat Motswedi Diamond in 2024, suggests that the age of spectacular diamond finds is far from over.
See the World’s Biggest Rough Diamonds
A visit to the Cape Town Diamond Museum offers a rare glimpse into the world of diamonds and diamond mining in South Africa, with exact, life-size replicas of the most famous diamonds and the biggest rough diamonds ever found, including the Cullinan, Heart of Eternity, and Hope Diamond. Book your guided tour today.
