When rough diamonds are cut and polished, they can lose up to 50% of their original size and carat-weight. While finding a large rough diamond is rare on its own, turning it into a high-quality, polished gem of substantial size is an even greater achievement.
Formed deep underground over billions of years, diamonds are natural treasures created by extreme heat and pressure. But not all diamonds are created equal. Only a few have gained global fame and legendary status for their immense size, clarity, and fascinating histories.
From royal jewels to record-breaking price tags, here’s a list of the world’s 10 largest polished diamonds, each one a masterpiece of nature refined by human hands.
10 Largest Cut Diamonds:
1. Golden Jubilee Diamond – 545.67 Carats
Origin: Premier Mine, South Africa (1985)
Rough: 755.5 carats
Current Location: Royal Museum, Bangkok, Thailand
The Largest Cut Diamond
The Golden Jubilee Diamond is the largest cut and polished diamond in the world. Discovered in 1985 at South Africa’s Premier Mine, it was originally an unattractive 755.5-carat rough stone called the “Unnamed Brown.” But beneath the surface lay a remarkable fancy-colour gem.
Cut by master diamond cutter Gabriel Tolkowsky, the diamond was shaped over two years in a vibration-free underground chamber. The result? A warm, fiery cushion-cut gem with a golden-brown hue and unmatched brilliance.
In 1995, it was gifted to King Bhumibol Adulyadej of Thailand for his Golden Jubilee celebration, transforming it into a national treasure. Today, the Golden Jubilee Diamond resides in Bangkok’s Pimammek Golden Temple.
2. Cullinan I – 530.4 Carats
Origin: Premier Mine, South Africa (1905)
Rough: 3,106 carats
Current Location: Tower of London (Sovereign’s Sceptre with Cross)
The Great Star of Africa
Born from the largest rough diamond ever discovered—3,106 carats—the Cullinan I dazzles with royal prestige. Cleaved and polished by Joseph Asscher, the diamond was gifted to King Edward VII as a peace offering from the South African government.
Mounted in the Sovereign’s Sceptre, this D-color gem radiates under the vaulted ceilings of the Tower of London. Its breathtaking size and symbolism make it a must-see for royal historians and diamond lovers alike.
3. The Incomparable Diamond – 407.48 Carats
Origin: Democratic Republic of Congo (1984)
Rough: 890 carats
Current Status: Private Collection
A Chance Discovery
The Incomparable Diamond is a uniquely shaped brownish-yellow fancy colour diamond discovered in the Democratic Republic of Congo in 1984. With a rough weight of 890-carats, a young girl found it by chance while playing in a pile of discarded mining rubble.
Masterfully cut by Marvin Samuels, the polished 407.48-carat stone became the largest internally flawless diamond ever graded by GIA at the time. Its notoriety grew when it was set into a necklace valued at $55 million, earning it a Guinness World Record.
4. Cullinan II – 317.4 Carats
Origin: Premier Mine, South Africa (1905)
Rough: 3,106 carats
Current Location: Tower of London (Imperial State Crown)
The Second Star of Africa
Cullinan II, often called the Second Star of Africa, is the second-largest polished diamond cut from the original Cullinan 3106-carat rough.
Crafted from the same legendary Cullinan rough, the Cullinan II rests at the front of the United Kingdom’s Imperial State Crown, worn during ceremonial occasions by the current monarch, King Charles III. Its cushion-cut brilliance and regal history make it one of the world’s most photographed diamonds.
5. Spirit of de Grisogono – 312.24 Carats
Origin: Central African Republic
Rough: 587 carats
Current Location: Private Ownership
The World’s Largest Cut Black Diamond
A mysterious black beauty in a world of colourless and fancy-colour brilliance, the Spirit of de Grisogono is the largest cut black diamond ever recorded.
Created using the ancient Mogul cutting technique, the diamond was set in a ring surrounded by 702 white diamonds and became a symbol of high-fashion luxury. Its unique color and massive size helped redefine the appeal of black diamonds in modern jewelry.
6. Graff Lesedi La Rona – 302.37 carats
Origin: Botswana (2015)
Rough: 1,019 carats
Current Location: Owned by Graff Diamonds
Modern Diamond-Cutting Technology
Cut from a 1,109-carat rough stone discovered in Botswana in 2015, the Graff Lesedi La Rona is one of the largest square emerald-cut diamonds ever created. Utilising modern diamond-cutting techniques, it was crafted using advanced laser mapping and cutting technologies. Its name, meaning “Our Light” in Setswana, honors Botswana’s diamond heritage. Today, it stands as a landmark achievement in modern diamond cutting.
7. De Beers Centenary Diamond – 273.85 carats
Origin: Premier Mine, South Africa (1986)
Rough: 599 carats
Current Status: Private Collection
D-Flawless Diamond
The De Beers Centenary Diamond is a D-flawless gem named in celebration of De Beers’ 100th anniversary. Cut over three years under the expert direction of Gabriel Tolkowsky, the diamond is known for its exceptional clarity and precision. Today, it remains in a private collection and is considered one of the most perfect diamonds ever cut.
8. Star of Sierra Leone – 242.50 carats
Origin: Sierra Leone (1972)
Rough: 968.9 carats
Current Status: Harry Winston Collection
The Largest Alluvial Diamond
The Star of Sierra Leone is the largest alluvial diamond ever discovered and the 3rd largest gem-quality rough diamond ever found, weighing 968.9-carats rough. It was later cut into 17 finished stones, with the largest being the 242.50-carat pear-shaped centerpiece.
Known as the “Valentine’s Day Diamond,” it was found on February 14th, 1972, and acquired by jeweller Harry Winston. The Star of Sierra Leone is an excellent example of an alluvial diamond with extraordinary purity.
9. Jubilee Diamond – 245.35 carats
Origin: Jagersfontein Mine, South Africa (1895)
Rough: 650.80 carats
Current Location: Private Collection
Mistaken for the Cullinan II
Originally mistaken for the Cullinan II due to its size and shape, this cushion-cut stone gifted in celebration of Queen Victoria’s Diamond Jubilee. Though now in a private collection, this 245.35-carat cushion-cut diamond was once owned by various royal figures and prestigious collectors, and has remained a staple in diamond history for its royal associations.
10. Millennium Star – 203.04 carats
Origin: Democratic Republic of the Congo, DRC (1990)
Rough: 777 carat
Current Location: De Beers Collection
A Timeless Symbol of Endurance
Discovered as a 777-carat rough stone, the Millennium Star was shaped by the Steinmetz Group into a 203.04 carat D-flawless pear-cut diamond of striking purity. The diamond gained further international attention when it was displayed at the London Millennium Dome in 2000. Remarkably, it survived a high-profile, attempted robbery, one of the boldest diamond heists in history.
Today, the Millennium diamond forms part of the De Beers Collection and remains a symbol of modern craftsmanship, resilience, and the enduring allure of perfection.
Learn More at the Cape Town Diamond Museum
Only about 30% of diamonds mined globally each year are considered gem-quality. And, of that 30%, fewer than 1% are large enough to be cut into stones of 1 carat or more. That’s why large cut diamonds are so rare and valuable, and why the world’s largest polished diamonds have become enduring symbols of history, status, and craftsmanship.
Want to learn more about diamond size or see exact replicas of the world’s biggest gems? Visit the Cape Town Diamond Museum, located at the Clock Tower Waterfront, for an immersive journey into the history of diamonds and South Africa’s rich diamond heritage.
FAQ: The Largest Polished Diamonds
What is the biggest polished diamond in the world?
The Golden Jubilee Diamond at 545.67 carats is the biggest polished diamond in the world.
What is the biggest rough diamond ever discovered?
The largest rough diamond ever discovered is the Sergio Carbonado, a 3167-carat black diamond (technically classified as a carbonado) that was later fragmented for industrial use.
What is the biggest gem-quality diamond ever discovered?
The Cullinan Diamond is the biggest gem-quality diamond ever found. Discovered in South Africa in 1905, the Cullinan rough was 3106-carats before being cut into 9 major pieces, including the Cullinan I and Cullinan II.
What is the biggest diamond in the British Crown Jewels?
Set in the Sovereign’s Sceptre, the Cullinan I is the biggest diamond in the British Crown Jewels. Both the Cullinan I and Cullinan II diamonds are part of the crown jewels.
Where can the public see the world’s largest diamonds?
The largest diamonds are held in museums, private collections, and royal jewels around the world. Visit the Tower of London (UK), Louvre Museum (France), and Royal Museum (Thailand) to see them. Or, visit the Cape Town Diamond Museum to see exact, life-size replicas up-close.
How are rough diamonds turned into polished diamonds?
A cut diamond, especially a brilliant-cut diamond, goes through various stages from mine to finger before it can be set in a jewellery piece. Rough diamonds are cut and polished by master artisans using a combination of science, skill, and art.
What is the most flawless diamond ever found?
The De Beers Centenary Diamond and the Millennium Star are both graded D-flawless. Based on rough carat-weight, the Millennium Star (777-carats) is the largest flawless diamond ever found.
What is the most expensive diamond necklace?
The Incomparable Diamond necklace, featuring the cut and polished 407.48 carat fancy-colour brownish-yellow Incomparable Diamond, is the most expensive diamond necklace valued at $55 million.
Why is South Africa famous for diamond discoveries?
Most of the world’s largest and most famous diamonds can be traced back to South Africa. The country home to the Golden Jubilee, the Cullinan, the Blue Heart of Eternity, and other incredible diamond discoveries. Today, South Africa remains one of premier sources for gem-quality diamonds worldwide.
