The Magnificent Mediterranean Blue Diamond Heads to Auction

Blue diamond lovers, take note: a fantastic example of the rare colored gemstone will be sold at Sotheby’s in Geneva this spring! Today, let’s take a closer look at the incredible Blue Mediterranean Diamond.

The rare diamond was discovered at the Cullinan mine in South Africa in 2023. That is, of course, the same mine that produced the incredible Cullinan Diamond in the early 20th century. Sotheby’s notes that the Cullinan mine is the most prominent source of blue diamonds globally today, though the number found is decreasing over time. The rough diamond, when discovered, weighed in at 31.94 carats. The stone was studied for over a year before it was cut and polished, and the process yielded a 10.03-carat diamond with a “cushion modified brilliant” cut.

Just how rare is a blue diamond like this one? Sotheby’s explains, “Less than 0.1% of any diamonds sourced show any evidence of blue colour and an infinitesimally small percentage of those is graded Fancy Vivid Blue.” The auction house compares the diamond to two others sold by them over the past decade: the Blue Moon of Josephine, a 12.03 carat cushion-shaped Internally Flawless Fancy Vivid Blue diamond that sold for $48.5 million USD in Geneva in 2015, and the De Beers Blue, a 15.10 step-cut Fancy Vivid Blue diamond that sold for $57.5 million USD in Hong Kong in 2022.

The diamond is currently set in a simple ring, shown here on a model in a press image shared by Sotheby’s. The solitaire ring setting includes no other gemstones. The model image does a good job of showing the size and scale of the gem.

And here’s a close-up photograph of the diamond in its ring setting. In the Sotheby’s press materials, a spokesperson for the Gemological Institute of America (GIA) offers some thoughts on the gem: “Like its namesake, the Mediterranean Blue is a symbol of nature’s eternal wonders. Its physical beauty, enhanced by the skill of a master cutter, is mesmerizing as is its blue colour, so rarely seen; only 0.3% of diamonds display a colour that would be described as predominately blue among all diamonds submitted to GIA annually and of those, only a small number are Fancy Vivid weighing 10 carats or more. The attributes of the Mediterranean Blue, weighing 10.03 ct in the most coveted fancy-color range, are absolutely exemplary for a diamond.”

The diamond will be auctioned by Sotheby’s in Geneva on May 13, 2025. Ahead of the sale, the diamond will be showcased to the media in a special preview in Abu Dhabi on April 8. Further exhibitions of the diamond will take place in Taipei, Hong Kong, and New York. The pre-auction displays are clearly geared toward reaching a particularly wealthy (and interested) clientele. Per a Sotheby’s representative, the diamond is expected to sell “in the region” of $20 million USD.