Ever wondered what the world’s biggest gem-quality diamond discoveries are? These impressive stones aren’t just beautiful, they’re colossal icons that have graced royal crowns and sceptres, broken jewellery sale records, and ‘rocked‘ the global diamond industry.
Formed deep within the Earth over billions of years under extreme heat and pressure, the world’s largest gem-quality diamonds (measured by their rough carat weight) each hold a story as remarkable as their size. From crowning kings to unbelievable stories of chance discoveries, these diamonds are true wonders of nature.
Here’s a list of the biggest gem-quality diamonds ever discovered:
From Biggest to Smallest:
The Cullinan: 3,106 ct
Origin: South Africa, 1905
Biggest Cut Gem: Cullinan I, 530.4 carats
Discovered in 1905 at the Premier Mine in South Africa, the Cullinan Diamond remains the largest gem-quality rough diamond ever found at 3106-carats. Named after Sir Thomas Cullinan, the mine’s owner, the diamond was gifted to King Edward VII and later cut in Amsterdam. The Cullinan produced 105 stones, including the famous Great Star of Africa (530.4 ct) and Second Star of Africa (317.4 ct), now part of the British Crown Jewels.
Lasedi La Rona: 1,111 ct
Origin: Botswana, 2025
Biggest Cut Gem: Graff Lesedi La Rona, 302.37 carats
The Lesedi La Rona is the fifth-largest diamond ever found and the largest highest colour, highest clarity diamond ever certified by the GIA. It was found in the South lobe of the Karowe mine in Botswana on November 16, 2015, making it one of the 21st century’s most remarkable diamond discoveries. The stone is a colourless/white type IIa diamond and remains the largest diamond found using modern machinery for automated diamond sorting.
The Excelsior: 995.2 ct
Origin: South Africa, 1893
Biggest Cut Gem: Excelsior I, 69.69 carats
Found in 1893 at the Jagersfontein Mine in South Africa, the Excelsior was once the world’s largest known diamond before the Cullinan was discovered in 1905. Its stunning blue-white hue made it stand out, though it was eventually cut into 21 polished stones, including the pear-shaped Excelsior I (69.69 ct) and the Marquise-shaped Excelsior III (46.9 ct). The Excelsior remains one of the most legendary finds in diamond history.
The Star of Sierra Leone: 968.9 ct
Origin: Sierra Leone, 1972
Biggest Cut Gem: Pear-shaped, 242.5 carats
The Star of Sierra Leone is the world’s largest alluvial diamond ever found, discovered in 1972 in Sierra Leone. Known for its extraordinary purity, the Star of Sierra Leone was purchased by famed jeweller Harry Winston. It was cut into 17 diamonds, 13 of which were classified as flawless—an incredible feat in the diamond world.
The Incomparable: 890 ct
Origin: Democratic Republic of Congo, 1980s
Biggest Cut Gem: The Incomparable, 407.48 carats
The Incomparable was discovered in the 1980s in the Democratic Republic of Congo by a young girl playing in a pile of mining rubble. Originally weighing 890 carats in its rough form, the diamond was later cut into a unique, step-cut shield shape weighing 407.48 carats. It remains one of the largest internally flawless diamonds ever graded.
The Koh-i-Noor Diamond: 793 ct
Origin: India, 13th Century
Biggest Cut Gem: Koh-i-Noor, 105.6 carats
Believed to have been discovered in the 13th Century, the Koh-i-Nor is one of the world’s most famous diamonds and the oldest known diamond discovery. Although the rough carat weight is unknown, the original Koh-i-Noor diamond is estimated yo have weighed 793 carats. After it was first cut, it was reduced to 186 carats. In 1852, it was recut to its current size of 105.6 carats to enhance its brilliance.
The Great Mogul: 787 ct
Origin: India, 17th Century
Biggest Gem: The Great Mogul (or Orlov), 280-carats
Believed to have been during the mid-1600s in India, from the Kollur Mine, the Great Mogul diamond is estimated to have originally been a 787-carat rough diamond, cut and shaped into a 280-carat rose cut, as described by Jean Baptiste Tavernier in 1665. Today, modern scholars are convinced that the Great Mogul is actually the Orlov Diamond, which is set in Catherine the Great’s imperial Russian sceptre.
The Millennium Star: 777 ct
Origin: Democratic Republic of Congo, 1990s
Biggest Cut Gem: Millennium Star, 203.04 carats
Discovered in the Democratic Republic of Congo in the 1990s, the Millennium Star is one of the rarest diamonds in the world. With flawless clarity and a perfect D colour grade, this 777-carat rough diamond was eventually polished into a 203.04-carat pear-shaped gem, making it the second-largest D-colour (colourless) diamond in the world. Today, it is owned by the De Beers Group and is considered one of the most valuable diamonds on Earth.
The Woyie River: 770 ct
Origin: Sierra Leone, 1945
Biggest Cut Gem: The Victory Diamond, 31.35 carats
Found in 1945 in Sierra Leone, the Woyie River diamond is one of the largest alluvial diamonds ever discovered. Named after the nearby river, Koidu, the diamond was cut into 30 smaller stones, including 10 gems weighing over 20 carats each. The largest gem, an emerald cut named the Victory Diamond (31.35 ct) to celebrate the victory of WWII, was worn by Queen Elizabeth II, further cementing its place in diamond history.
The Golden Jubilee: 755 ct
Origin: South Africa, 1985
Biggest Cut Gem: Golden Jubilee, 545.67 carats
Discovered in 1985 at South Africa’s Premier Mine, the Golden Jubilee holds the title of the world’s largest faceted diamond. Originally a brown diamond with surface cracks, it was transformed through masterful polishing into a stunning 545.67-carat cushion-cut gem. It was later gifted to the King of Thailand and remains part of the Thai Royal Family’s collection.
See the World’s Biggest Rough Diamonds
Today, the world’s biggest and most famous diamonds are housed in private collections, displayed in museums, and featured in crown jewels all around the world. But you have the chance to see them all in one location.
At the Cape Town Diamond Museum, guests can see exact, life-size replicas of the world’s largest diamonds and iconic gems like the the Cullinan Diamond, the Blue Heart Diamond, and other legendary stones, up-close and in-person.
Your tour also includes a guided and immersive journey through the fascinating world of diamonds: from their formation deep beneath the Earth’s surface to their role in South Africa’s rich diamond history. Visitors will also have the chance to witness the diamond cutting and polishing process firsthand, complete with a personalised viewing at the Shimansky diamond showroom located at the Clock Tower Waterfront.
Rated the best museum experience in Cape Town, don’t miss out! Book your tour today.
