Diamonds come in a variety of colors, with blue being one of the rarest and most valuable. Blue diamonds get their color from trace amounts of the element boron present in their crystal structure. The more boron present, the bluer the diamond will appear. Blue diamonds range from pale sky blue to deep steely grayish-blue in color. The exact shade depends on factors like the diamond’s chemical composition and how the stone is cut. Blue diamonds are extremely rare in nature, making up less than 1% of mined diamonds. Their rarity and beauty make them some of the most prized diamonds in the world.
What Causes the Blue Color in Diamonds?
In nature, most diamonds form colorless or with a yellowish tint. This is because they are composed almost entirely of carbon with very little impurities. Diamonds owe their blue color to the presence of the element boron in their crystal structure. Boron atoms mixed in with the carbon atoms act as color centers that absorb light in the yellow region of the spectrum, causing diamonds to transmit blue light. The more boron present, the more intense the blue coloration. Blue diamonds contain anywhere from 20 to 300 parts per million of boron. In comparison, most colorless diamonds have 1 part per million or less of impurities. The rare conditions needed to facilitate boron incorporation during diamond formation make blue diamonds very uncommon. Only a handful of mines around the world have produced these precious blue gems.
Range of Blue Diamond Colors
Blue diamonds occur in various shades ranging from pale sky blue to deep steely bluish-gray. The exact hue depends on factors like:
– Concentration of boron – More boron leads to a stronger blue color.
– Presence of other impurities – Hydrogen or nitrogen impurities can modify the blue color.
– Cut of the diamond – Different cuts can accentuate or diminish the saturation of the blue color.
Here are some of the various shades that blue diamonds can display:
– Fancy Light Blue – These diamonds have a light sky blue color. They have the lowest saturation among blue diamonds.
– Fancy Blue – These have a saturated pure blue color similar to topaz. This is the most common and sought after shade of blue diamond.
– Fancy Dark Blue – These diamonds lean towards a navy blue color with stronger color saturation.
– Fancy Deep Blue – The deepest blue color, close to sapphire blue but slightly grayer. Very rare and valued.
– Fancy Grayish Blue – These diamonds have a grayish-blue hue. The blue color is diluted by the gray undertone.
– Fancy Vivid Blue – The most saturated and intense blue color. These rare diamonds exemplify the classic cobalt blue color of blue diamonds.
Natural Occurrence of Blue Diamonds
Natural blue diamonds are extremely rare. They make up less than 1% of diamonds mined globally. The vast majority of diamonds unearthed are light yellowish or brownish in color. Truly colorless diamonds only account for about 15-20% of finds. Out of these white diamonds, blue diamonds constitute less than 0.1%. Such minuscule quantities contribute to the extraordinarily high value of blue diamonds.
For a diamond to form blue, very specific conditions are required during its creation in Earth’s mantle. Boron must be present in the carbon source where diamonds form. The growth environment also needs to be free of hydrogen and nitrogen impurities that could interfere with the blue color. Most diamond deposits do not provide this unusual geochemistry. As a result, large scale blue diamond mining only occurs in a handful of locations worldwide.
The earliest source was India’s Golconda mines, which produced the legendary Hope Diamond. Current major producers include:
– Cullinan Mine (South Africa)
– Argyle Mine (Australia) – Now closed, was the main source of blue diamonds like the Red Cross Diamond.
– Mir Mine (Russia) – Yielded diamonds like the 26 carat Oppenheimer Blue.
– Letseng Mine (Lesotho) – Known for large high quality blue diamonds.
Blue diamonds occasionally turn up in other mines but in very sparse quantities. Recently, blue diamond discoveries have been made in Blue Moon mine in the US and Karowe mine in Botswana.
Grading Scale for Blue Diamonds
Like other colored diamonds, blue diamonds are graded by the intensity of their color using the following scale:
| Color Grade | Intensity Level |
| Fancy Light | Very light color, pale blue |
| Fancy | Medium to strong blue color |
| Fancy Intense | Saturated and vivid color |
| Fancy Dark | Darker blue but slightly desaturated |
| Fancy Deep | Very strong deep blue color |
Besides the intensity, color distribution and quality factors like clarity and cut grade also impact value. A well cut blue diamond that displays a pure evenly distributed blue color commands the highest prices.
High Value of Top Quality Blue Diamonds
High quality blue diamonds are one of the most expensive diamonds in the world, even more prized than colorless diamonds. Per carat prices for investment quality blues can rival or exceed those of colorless diamonds. Here are some factors that contribute to the steep pricing:
– Rarity – Their exceptionally low availability in nature results in high prices.
– Desirability – The mystique and allure surrounding famous blues like the Hope Diamond fuel demand.
– Production limits – The Argyle mine, which was the main source of world’s blues, shut down in 2020 further reducing supply.
– Rich color – Saturated blue color is more sought after than pale shades.
– Branding – Being able to claim ‘world’s most expensive diamond’ allows brands to charge huge premiums.
Some record sales illustrate the astronomical valuations of top blue diamonds:
– 14.62 carat Oppenheimer Blue sold for $57.5 million in 2016 – $3.93 million per carat.
– 15.10 carat Pink Star sold for $71.2 million in 2017 – $4.71 million per carat.
– 18.96 carat Winston Blue sold for $23.8 million in 2014 – $1.25 million per carat.
For comparison, average price per carat for a high quality colorless diamond is around $15,000-25,000. While still luxurious, blue diamonds are clearly in a league of their own when it comes to pricing.
Enhancement and Treatment of Blue Diamonds
Natural blue diamonds are incredibly rare. However consumer demand for blue diamonds has led to some treatments and enhancements to produce more supply. Common methods include:
– Artificial Irradiation – Colorless diamonds are exposed to radiation to produce blue color centers. However, the color is often uneven.
– High Pressure High Temperature Treatment (HPHT) – Mimics conditions during diamond formation to infuse blue coloring.
– Fracture Filling – Filling fractures with colored resins to improve apparent color. This is impermanent.
– Coatings – Blue-tinted coatings applied to improve appearance. Wears off over time.
Such treatments are legal as long as they are disclosed. Unfortunately, some unscrupulous sellers do not reveal treatments. Purchasing certified untreated natural blue diamonds from reputable sources ensures genuine blue color. Opting for third-party grading reports like from the GIA is recommended to authenticate that blue diamonds are real, untreated specimens.
Famous and Historic Blue Diamonds
Some of the world’s most famous diamonds are blue diamonds revered for their splendor, mystique and history. A few legendary blues include:
– Hope Diamond – This 45.52 carat diamond was mined in India in the 1600s. Infamous for its supposed curse but prized for its rare deep blue color.
– Wittelsbach Diamond – Originating from India’s Golconda mines, this 35.56 carat diamond adorned European royalty before being sold for $24.3 million in 2008.
– Heart of Eternity – A 27.64 carat blue diamond found in South Africa’s Premier Mine in 2000. It was cut into a heart shape and sold for $16 million.
– Blue Moon – Discovered in South Africa in 2015, this 12.03 carat cushion-cut diamond was rated Fancy Vivid Blue by the GIA and sold for $48 million.
– Tereschenko Diamond – Weighing 42.92 carats, this historic pear-shaped stone once decorated Russian nobility and later British royalty.
– Oppenheimer Blue – 14.62 carat vivid blue diamond sold by Christie’s auction in 2016 for a record $57.5 million.
Comparison to Other Colored Diamonds
Blue diamonds stand out as exceptionally rare even among fancy color diamonds. Other natural diamond colors like yellow, brown and gray occur much more frequently. Unique shades like pink, red and green also arise from structural imperfections and are far more attainable than blue diamonds. Here is how blue diamonds compare:
| Diamond Color | Frequency of Occurrence |
| Yellow/Brown | Most common – about 98% of diamonds |
| Colorless | Rare – 1-2% of diamonds |
| Pink | Extremely rare – 0.1% of diamonds |
| Red | Rarest diamond color – fewer than 20 stones exist |
| Blue | More rare than red – well under 0.1% of diamonds |
While still very expensive, colored diamonds like pinks and yellows can be found much more readily than blue diamonds. Top quality reds also command higher prices per carat than blues in some cases. However, blue diamonds remain unmatched in their prestige and mystique.
Suitability for Jewelry
The intense, opaque color of blue diamonds make them well suited for jewelry use. Their high refractive index results in exceptional brilliance and fire. Blue diamond jewelry highlights:
– Complementary settings – White metal settings like platinum or white gold allow the blue diamond color to take center stage.
– Halo settings – Surrounding blue diamonds with smaller white diamonds maximizes light return for greater sparkle.
– Statement pieces – Larger blue diamonds work well as solitaire pendants or earrings to make a bold fashion statement.
– Eternity bands – Blue diamonds alternating with white diamonds creates color contrast in wedding and anniversary rings.
– Men’s jewelry – Blue diamonds lend color in men’s accessories without being overly showy.
However, the exorbitant cost of large natural blue diamonds limits jewelry applications. Most blue diamond jewelry uses smaller accent stones under 5 carats. Synthetic blue diamonds offer an affordable alternative for larger jewelry pieces.
Synthetic Blue Diamonds
With natural blue diamonds occurring in such minute quantities, scientists have worked to artificially produce blue diamonds in labs. While synthetics were developed in the 1970s, major progress has recently been made in growing gem-quality blue diamonds. Synthetic blue diamond methods include:
– HPHT – High temperature and pressure duplicate natural conditions to grow blue diamonds with boron.
– CVD – Chemical vapor deposition allows adding boron during carbon deposition to form blue diamonds.
– Irradiation – Exposing colorless CVD diamonds to radiation turns them blue.
Pros of synthetic blue diamonds:
– Lower price – Large synthetic blues costs much less than natural counterparts.
– More supply – Production can be scaled up to meet demand.
– Identical properties – Lab blues have the same hardness, brilliance and fire as natural stones.
Cons of synthetic blue diamonds:
– No resale value – Synthetics have little value on secondary market.
– Not as prestigious – Synthetic origin is less exclusive than natural stones.
– Disclosure required – Sellers must reveal lab origins or could be accused of fraud.
Synthetic blue diamonds offer an ethical, eco-friendly alternative. But natural blue diamonds still retain the prestige and investment value.
Conclusion
In summary, blue diamonds derive their captivating color from trace boron impurities. Their rarity and mystique lead to huge prices, especially for larger vivid blue stones. Blue diamond’s stunning hues and high brilliance make them ideal for fashioning into jewelry. While more affordable synthetic blue diamonds are available, natural blue diamonds remain the crème de la crème of the diamond world.