Beauty of Blue: Ultimate Guide to Buying Blue Diamonds
Learn more about blue diamonds and take a closer look at some of our recent favorite blue diamonds.
Brief History of Blue Diamonds
The earliest known blue diamonds were found in the Kollur mine in the Golconda region of India. Famous blue diamonds from this region include the Idol’s Eye (15th century) and the Hope Diamond (17th century). 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 but nitrogen also plays a role in determining the intensity of the color. 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 dark blue color.
Blue diamonds are mined Cullinan Mine in South Africa and Orapa Mine in Botswana. The Argyle Mine in Australia was also a source of high quality blue diamonds until it closed in 2020.
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 Fancy Vivid Blue $20 million Estimate
In May 2025, Sotheby's will auction The Mediterranean Blue, a Fancy Vivid Blue, Natural Color, VS2 Clarity, Type IIb diamond weighing 10.03 carats. The Mediterranean Blue is a type IIb diamond which signifies that a small amount of the trace element boron is present in its chemical composition. Boron in turn contributes strongly to the blue appearance of the diamond, which is also related to exposure to high pressure during the formation process. Under cross-polarized light, The Mediterranean Blue displays a type of strain known as cross-hatched or “tatami” strain, commonly seen in type IIb diamonds. The Mediterranean Blue diamond started as a 31.93 rough diamond sourced in South Africa and is described as "a remarkable example of one of the rarest color sensations observed in a diamond." A cushion-shape was chosen in honor of many historical diamonds, such as the Régent and Cullinan II diamonds, the cutter placed the gem in an ongoing dialogue with these storied gems of the past. The diamond’s Vivid Blue color is perfectly offset by its classic, elegant cushion-shape with harmoniously softened edges.
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
In April, Sotheby's sold a Fancy Intense Blue Green Diamond for 4.3 million HKD ($560,000). 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.
Fancy Intense Blue Diamond 1.01 Carats $360,000
In May, Sotheby's sold a Fancy Intense Blue Diamond for 317,500 CHF ($360,000). The Marquise Fancy Intense Blue Diamond is 1.01 Carats, Natural Colour, VS1 Clarity. We love the simple and elegant east west setting of this Marquise Fancy Intense Blue Diamond.
Harry Winston Faint Blue Diamond 7.13 Carats $348,000
In June, Sotheby's sold a Harry Winston Faint Blue Diamond for $348,000. The Pear Shaped Faint Blue Diamond is 7.13 Carats, Natural Color and VS2 Clarity. While the more intense color diamonds are rarer, increasingly collectors are looking for blue diamonds in all intensities with some preferring the faint color since blue diamonds are the rarest of the colored 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 Sotheby's 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.
Buy and Selling Blue Diamonds at Sotheby's
Sotheby's often has impressive blue diamonds available at auction, including fancy intense and fancy vivid blue diamonds. If you don't want to wait until the next auction, Sotheby's also has a curated selection of high quality blue diamonds available for immediate purchase. If you would like to source a special High Jewelry blue diamond ring or other blue diamond jewelry, a salon specialist would be happy to assist. Sotheby's also provides custom high jewelry services and custom engagement ring services with loose blue diamonds. Sotheby's is able to source rare and impressive blue diamonds from its global supplier network so contact a salon associate or specialist for more details. Sotheby's is always sourcing the most exquisite blue diamonds.
- Explore upcoming jewelry auctions in New York, London, Switzerland, Paris, and Hong Kong.
- Contact a Salon Associate in New York, Zurich or Hong Kong to schedule an appointment.
- Speak to a Jewelry Specialist about selling a Blue Diamond.
Trust our worldwide network of leading jewelry specialists from a globally renowned auction house established in 1744.
