What Is the Rarest Diamond on Earth
The rarest diamond on Earth is typically a Type IIa diamond with exceptional color, such as a vivid red, blue, or pink stone. These diamonds have minimal nitrogen impurities and extremely rare crystal lattice defects that create color, making them scarce in nature. The Gemological Institute of America classifies Type IIa diamonds as chemically pure and structurally perfect, which is why they command the highest premiums among collectors and investors.
In terms of market value, the rarest diamond on Earth can sell for tens of millions of dollars per carat at auction. The Pink Star, a 59.60-carat vivid pink diamond, set a world record in 2017 when it sold for over $71 million, according to Sotheby's. Other famous stones like the Oppenheimer Blue and the Winston Blue have reinforced the idea that flawless, intensely colored diamonds are the rarest and most expensive category in the gem market.
Types and Colors of the Rarest Diamonds
Red Diamonds
Red diamonds are considered the rarest color in the diamond world, with only a few gem-quality stones known to exist. The Moussaieff Red, a 5.11-carat trilliant-cut red diamond, is one of the most famous examples, and its origin is traced to the Argyle mine in Western Australia, which has since ceased production. Because of their extreme scarcity, red diamonds rarely appear at auction, and when they do, they attract intense bidding from elite collectors and institutions.
Blue and Pink Diamonds
Blue diamonds get their color from trace amounts of boron, while pink diamonds are thought to result from a distortion in the crystal lattice during formation. The Hope Diamond, a 45.52-carat deep blue diamond housed at the Smithsonian, is one of the most famous blue stones and illustrates how boron traces create the rarest blue hues. Pink diamonds from the now-closed Argyle mine, such as the Williamson Pink Star, have achieved record prices, reinforcing their status as some of the rarest colored diamonds on Earth.
Where the Rarest Diamonds Are Found and Who Mines Them
The rarest diamond on Earth has historically come from a small number of mines, most notably the Argyle mine in Western Australia, which produced over 90% of the world's pink and red diamonds before it closed in 2020. Other notable sources include the Cullinan mine in South Africa and alluvial deposits in Brazil and Central Africa, but these yield far fewer gem-quality stones with exceptional color and clarity.
Major companies such as Rio Tinto, which operated the Argyle mine, and Lucara Diamond Corp, which recovered the legendary Lesedi La Rona rough stone, dominate the supply of ultra-rare diamonds. Auction houses like Sotheby's and Christie's regularly handle the most significant stones, with private sales often occurring through firms such as Graff Diamonds and De Beers. For investors, the rarity and fixed supply of these diamonds make them a unique alternative asset, though direct ownership requires navigating high barriers to entry and limited liquidity, as noted by industry analysts and financial regulators.