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Beauty of Blue: Ultimate Guide to Buying Blue Diamonds
Discover the allure of blue diamonds in this ultimate guide. Explore their rarity, value, and how to buy the perfect blue diamond with expert tips and insights.
Brief History of Blue Diamonds
The earliest known blue diamonds were found in the Kollur mine in the Golconda region of India. Historically, blue diamonds were recovered mainly in India and Brazil. For the last 100 years, they have also been randomly and sporadically found in the Premier Mine (since renamed the Cullinan Mine) in South Africa. Blue diamonds make up less than 0.02 percent of all natural mined diamonds. Like other colored diamonds, blue diamonds are valued based on the clarity and intensity of the color first, followed by the size and finally the cut quality.
Blue diamonds are among the rarest colored diamonds. Blue diamonds get their color from the element boron, though nitrogen can also influence the intensity of the hue. The boron replaces some of the carbon in the diamond crystal structure and can produce anything from a very light hint of blue to a deep, saturated tone.
Blue diamonds are mined at the Cullinan Mine in South Africa and the Orapa Mine in Botswana. The Argyle Mine in Australia was also a source of high quality blue diamonds until it closed in 2020.
Key Takeaways: Blue Diamonds
| Feature | Overview |
| Upcoming Auction Highlight | A 6.03 carat Fancy Vivid Blue diamond will headline Sotheby’s High Jewelry sale in Geneva on May 12, 2026 |
| Rarity | Natural blue diamonds make up less than 0.02% of all mined diamonds, making them among the rarest gemstones in the world |
| Source of Color | Blue diamonds get their color from trace amounts of boron within the crystal structure |
| Key Sources | Historically found in Golconda (India), and more recently in Cullinan Mine (South Africa) and Orapa Mine (Botswana) |
| Color Grading | GIA grades range from Faint Blue to Fancy Deep Blue, with Fancy Vivid and Fancy Deep being the most desirable |
| Popular Shapes | Cushion, pear, oval, and radiant cuts are preferred to enhance color saturation |
| Type IIb Diamonds | Most natural blue diamonds are Type IIb, an extremely rare category known for exceptional purity |
| Pricing | Prices can range from $30,000 per carat for faint blues to over $1M per carat for Fancy Vivid stones |
| Collector Appeal | Extreme rarity, royal history, and auction records make blue diamonds highly coveted among collectors |
Blue Diamond Grading
A blue diamond is graded and classified based on several key criteria like white diamonds including color, clarity, cut, and carat weight. Color grading of blue diamonds is the most important aspect influencing pricing for a blue diamond. Colors are classified by the hue or the actual color of the diamond including secondary hues such as greenish-blue, grayish-blue and violet-blue. Tone is another factor that can vary from very light to very dark. Finally the saturation is the strength of the color. A blue diamond with high saturation or more vivid are more desirable in the market. Clarity, cut and carat weight grading is the same as other diamonds.
The Gemological Institute of America (GIA) uses the following categories to describe the color of blue diamonds:
- Faint Blue
- Very Light Blue
- Light Blue
- Fancy Light Blue
- Fancy Blue
- Fancy Intense Blue
- Fancy Vivid Blue
- Fancy Deep Blue
Blue diamonds that are graded Fancy Vivid Blue and Fancy Deep Blue are the most intense in color and are also the most coveted. Fancy Vivid specifically describes a blue diamond that is medium to dark in tone and strong to very strong in saturation. In a past GIA study of 462 blue diamonds, only 1% were Fancy Vivid.
Blue diamonds are also graded on a clarity scale similar to white diamonds from Flawless to Included. Cut grading is also similar to white diamonds including the proportions, symmetry and polish. The most popular fancy shapes for blue diamonds include cushion, radiant, oval, and pear, as these enhance the color and minimize waste during cutting. Carat weight is also the same as white diamonds. Sotheby's recommends only buying blue diamonds with a GIA certificate.
Cutting Blue Diamonds
The cutting process for blue diamonds is not analogous to near-colourless diamonds, or any other coloured diamonds for that matter. Blue diamonds usually occur as irregular, asymmetrical crystals. The blue colour may also be unevenly distributed throughout the rough crystal. Therefore, careful study of the crystallographic directions of the rough, and the properties of the stone, are needed to bring out the full potential of its colour and overall appearance. A high level of experience and expertise are therefore needed to cut and polish a blue diamond. To achieve the best possible visual appearance, expert diamond cutters often make modifications to traditional cutting styles.
Favorite Blue Diamonds Sold at Sotheby's
Every year, Sotheby's has the opportunity to sell some of the rarest blue diamonds at often record breaking prices. Blue diamonds are sought after by collectors for their rarity and historical ties to royalty like the Hope Diamond and the Wittelsbach-Graff Diamond. Additionally blue diamonds have long been symbols of wealth and power and have been prominently set in crowns, scepters and royal jewelry for coronations, weddings and other royal celebrations.
Take a closer look at our favorite blue diamonds.
The Mediterranean Blue, 17,860,000 CHF
The Mediterranean Blue sold for 17,860,000 CHF ($21.5 million) in May 2025. This extraordinary 10.03-carat cushion-modified brilliant-cut diamond was renowned for its striking Fancy Vivid Blue color and exceptional clarity. Mined in South Africa, it began as an impressive 31.93-carat rough before being meticulously transformed into its final cushion shape. The cutting process, which spanned over six months, was carefully documented, preserving a unique photographic record of the diamond’s remarkable journey. Classified as Type IIb, a rare category known for its distinctive blue hue, the Mediterranean Blue displayed an exceptional intensity of color and clarity, standing out as a remarkable example of nature’s artistry. Its sale marked a testament to the expertise and precision required to shape one of the world’s most coveted and rare colored diamonds.
Fancy Light Blue Diamond Ring 5.83 Carats, 1,206,500 CHF
This Fancy Light Blue Diamond Ring sold for 1,206,500 CHF ($1.5 million) in May 2025. The ring featured an exquisite 5.83-carat oval-shaped diamond of Fancy Light Blue color, accented by two heart-shaped diamond shoulders. Accompanied by a GIA report confirming its natural color and Internally Flawless clarity, the center stone stood out for its soft yet captivating hue. The two heart-shaped side diamonds, weighing 0.52 and 0.50 carats respectively, were also certified by the GIA as D color and Internally Flawless—adding to the ring’s overall rarity and elegance. This refined and romantic composition underscored the enduring appeal of colored diamonds in timeless settings.
Fancy Blue Diamond Pendent Necklace 4.05 Carats, 952,500 CHF
This Fancy Blue Diamond Pendent Necklace sold for 952,500 CHF ($1.1 million) in May 2025. Showcasing a beautifully cut 4.05-carat heart-shaped diamond of Fancy Blue color, the pendant was suspended from a classic cable-link chain measuring approximately 420mm in length. The diamond’s captivating hue and symmetrical heart shape lent the piece both charm and sophistication. Accompanied by a GIA report confirming its Fancy Blue, Natural Colour, and Internally Flawless grade, the diamond was also classified as Type IIb—a rare and highly sought-after category of blue diamonds known for their exceptional purity and conductivity. The necklace offered a romantic yet refined expression of one of nature’s rarest treasures.
Toi et Moi Pear Shaped Fancy Intense Blue Diamond Ring, $930,000
In May, Sotheby's sold a Toi et Moi ring featuring a Fancy Intense Blue Diamond for 825,500 CHF ($930,000). The Pear Shaped Fancy Intense Blue Diamond is 3.03 Carats, Natural Colour, I1 Clarity. The ring also features a pear shaped 2.82 carat white diamond that is D Color, VVS1 Clarity. This unique setting was all about the blue diamond and increasingly Toi et Moi rings are popular with modern brides as an alternative to the single solitaire engagement rings.
Fancy Grayish Blue Diamond 3.32 Carats, $720,000
In December, Sotheby's sold a marquise fancy grayish blue diamond for $720,000. The natural diamond is 3.32 carats and SI1 clarity and is unmounted.
Fancy Intense Blue Green Diamond 3.02 Carats, $560,000
This Fancy Intense Blue Green Diamond sold for 4.3 million HKD ($560,000) in April 2024. The Cut Cornered Rectangular Modified Brilliant Cut Fancy Intense Blue Green Diamond is 3.02 Carats, Natural Colour, VS1 Clarity. This Blue Green Diamond at 3 carats is rare in both size and secondary hue that makes this diamond a truly special stone.
Honorable Mention: 6.03 Carat Fancy Vivid Blue Diamond
Among the exceptional blue diamonds soon to appear on the market is a remarkable 6.03 carat Fancy Vivid Blue cushion-shaped diamond, a true rarity within one of the most coveted color grades in the world of gemstones. Stones of this caliber are most often associated with the historic Cullinan mine in South Africa, a legendary source responsible for producing some of the most important blue diamonds ever discovered. With its vivid saturation and classic cushion shape, reminiscent of iconic stones such as the Hope Diamond, this example captures the extraordinary beauty and scarcity that define Fancy Vivid Blue diamonds.
This exceptional diamond will be offered in Sotheby’s High Jewelry sale in Geneva on May 12, 2026, presenting collectors with a rare opportunity to acquire a gemstone that embodies the enduring allure and significance of the world’s most prized blue diamonds.
Blue Diamond Price
The price of natural blue diamonds varies widely but in general are priced significantly higher than comparable clarity and carat weight white diamonds and other colored diamonds. Only about 0.02% of all diamonds that are mined are naturally blue. The Hope Diamond is the most famous blue diamond and is 45.2 carat fancy deep greyish blue Type IIb diamond valued at over $200 million.
The most expensive blue diamond sold by Sotheby's was in 2022 for $57.5 million. The De Beers Blue diamond is a step cut 15.10 carat Fancy Vivid Blue, Internally Flawless and a Type IIb diamond. The six most expensive blue diamonds sold at auction have ranged from $25.8 million to $57.5 million.
The price for a 1 carat blue diamond can range from $30,000 to $50,000 for Faint Blue to over $1 million for a Fancy Deep Blue diamond. A 1.01 Carat Fancy Gray Blue Diamond sold for $190,000 in 2021 while a 1.08 Carat Pear Shaped Fancy Vivid Blue Diamond sold for $930,000. Blue diamonds that are Fancy Intense Blue and higher color grade can easily exceed $1 million per carat.
Frequently Asked Questions about Blue Diamonds
Why are blue diamonds so rare?
Blue diamonds are among the rarest gemstones in the world, accounting for less than 0.02% of all natural diamonds mined. Their color forms only when trace amounts of boron replace carbon atoms in the diamond’s crystal structure, a rare geological occurrence.
What causes the color in blue diamonds?
The distinctive blue hue comes from the presence of boron impurities within the diamond. Boron absorbs certain wavelengths of light, allowing blue tones to become visible.
How are blue diamonds graded?
Like other diamonds, blue diamonds are evaluated based on color, clarity, cut, and carat weight. However, color intensity is the most important factor. The GIA grading scale includes Faint Blue, Light Blue, Fancy Light, Fancy Blue, Fancy Intense, Fancy Vivid, and Fancy Deep.
What are the most valuable blue diamond color grades?
The most coveted blue diamonds are those graded Fancy Vivid Blue or Fancy Deep Blue, which display strong saturation and medium to dark tone.
What shapes are most common for blue diamonds?
Fancy shapes such as cushion, radiant, pear, and oval cuts are most common because they help intensify the diamond’s color while minimizing rough diamond loss during cutting.
Buy and Sell Diamond Jewelry with Sotheby’s
Whether you're a seasoned collector or new to fine jewelry, Sotheby’s offers a trusted, seamless way to buy and sell diamond jewelry on the secondary market.
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Purchase online or in person at our locations in New York, Paris, and Hong Kong, or work with a dedicated jewelry concierge to view or source specific diamond jewelry. - Exceptional Value
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