Stone of the Month : Blue Diamond
Some gemstones are admired.
Blue diamonds mesmerize.
Not because they sparkle more, but because they seem almost unnatural. A blue diamond does not flirt. It holds its ground.
Chemistry
A diamond turns blue because of boron. During formation, trace amounts of boron entered the diamond’s crystal lattice. Boron absorbs red light, allowing blue wavelengths to dominate. The result is not a surface tint but an intrinsic structural color.
Boron is an odd ingredient for a gemstone. Much of it was forged in violent cosmic collisions. On Earth, it lingers in seawater. The element behind blue diamonds carries both violence and stillness. Even at the atomic scale, blue diamonds has its own way to tell a story
Blue diamonds represent only a small fraction of global diamond output. Most mines will never produce one. Most people will never even see one.
Color & Size
Like all diamonds, not every blue diamond is equal. Grading ranges from Fancy Light to Fancy Vivid, and saturation matters more than size. A smaller stone with intense, evenly distributed color can surpass a larger but weaker one in value.
At auction, Fancy Vivid Blue diamonds sit at the very top of the market. The Blue Moon of Josephine, a 12.03-carat stone, sold for 48.4 million dollars at Sotheby’s Geneva in 2015. The buyer, Hong Kong collector Joseph Lau, named it after his 7 years old daughter.
A year later, Christie’s Geneva sold the 14.62-carat Oppenheimer Blue for 57.5 million dollars, named after the previous owner and of course discovered by De Beers.
Both stones are associated with the Cullinan Mine in South Africa, one of the rare geological deposits capable of producing diamonds of such intensity.
A Symbolic Color
Blue diamonds carry weight that exceeds their mass. That weight is psychological.
In Western visual culture, blue has long been associated with distance and hierarchy. Ultramarine pigment, made from ground lapis lazuli imported from Afghanistan, was once more expensive than gold. During the Renaissance, its use was often reserved for sacred figures. Painters such as Giotto or Titian dressed the Virgin Mary in ultramarine blue not only for symbolism, but because patrons had to pay for it separately.
When that color appears in a diamond, a material already linked to permanence, the effect intensifies. In high jewelry, major blue diamonds are rarely overwhelmed by design. Houses such as Harry Winston, Cartier, and Graff typically mount them in platinum with minimal surrounding color, allowing the stone to dominate.
The ultimate Legend
Some gemstones are rare. Very few become cultural icons. The Hope Diamond belongs to the latter.
Now housed at the Smithsonian in Washington, it is one of the very few jewels recognized far beyond the world of collectors.
Weighing 45.52 carats in its current form, the stone was likely mined in India in the 17th century and acquired by French merchant who later sold it to King Louis XIV. Recut and stolen during the French Revolution, it resurfaced decades later in London, it eventually entered the collection of banker Henry Philip Hope, from whom it takes its name.
Its legend was built by storytelling. In the early 20th century, jewelers and journalists popularized the idea that the diamond carried a curse, linking it to royal misfortune, bankrupt collectors, and mysterious deaths. Much of this narrative was exaggerated or fabricated, yet it proved irresistible. Long before science explained why diamonds could be blue, mythology had already made this one unforgettable.
New Kid on the block
In January 2026, Petra Diamonds announced the recovery of a 41.82-carat blue rough at the Cullinan mine. Still uncut, the stone exists only as potential. With blue diamonds, the real drama happens during cutting, Collectors , Auctions Houses and Jewlers are in for quite a ride !
