Christie’s has announced two exceptional natural blue diamonds for its upcoming Magnificent Jewels Auction sale at Rockefeller Center on June 9, highlighting the extraordinary rarity and complexity of the natural coloured diamond market.

Leading the sale is the Azure Blue, a remarkable 31.62-carat pear-shaped Fancy Blue diamond described by Christie’s as the largest Fancy Blue diamond ever offered at auction. The stone carries a pre-sale estimate of USD $6.5 to $8.5 million. Interestingly, sharing almost the identical estimate is a second diamond in the same auction: a 5.04-carat Fancy Vivid Blue marquise-cut diamond. Despite the dramatic size difference, the valuations sit within the same range, illustrating the immense importance of colour grading in the rare blue diamond market.

Natural blue diamonds derive their colour from boron, a trace element incorporated into the diamond’s crystal structure during formation deep within the Earth’s mantle. Boron causes selective absorption of red, orange, and yellow light wavelengths, leaving blue wavelengths dominant to the human eye.

Blue diamonds are exceptionally rare, predominantly occurring within the Type IIb category, which accounts for fewer than 0.1 per cent of all natural diamonds. Many Type IIb diamonds also possess electrical conductivity, a highly unusual physical property rarely seen in gem materials.

Within the blue diamond category, colour saturation is one of the most significant drivers of value. GIA grades blue diamonds across a spectrum including Fancy Light, Fancy, Fancy Intense, Fancy Vivid, Fancy Deep, and Fancy Dark. Among these, Fancy Vivid Blue represents the highest level of saturation and rarity found in nature.

The Azure Blue carries a Fancy Blue grade, combined with exceptional size and clarity, reportedly potentially Internally Flawless. It is a stone of immense importance for collectors and connoisseurs alike. However, the 5.04-carat marquise achieves the far rarer Fancy Vivid Blue grade, alongside VVS2 clarity and Type IIb classification. That single grading distinction effectively compensates for the significant size difference between the two stones, explaining why Christie’s has valued them similarly.

The Azure Blue is mounted in a platinum ring featuring a concealed halo of natural pink diamonds, while the 5.04-carat Fancy Vivid Blue marquise is set in platinum with baguette-cut side diamonds. Both mountings are intentionally understated, allowing the diamonds themselves to remain the focal point.

Recent auction history demonstrates the extraordinary premiums achieved by the finest Fancy Vivid Blue diamonds. In May 2023, the The De Beers Blue sold at Sotheby’s Geneva for USD $57.5 million, achieving approximately USD $3.8 million per carat. Prior to that, the The Oppenheimer Blue achieved the same price at Christie’s Geneva in 2016, becoming the most expensive jewel ever sold at auction at the time.

In 2015, the Blue Moon of Josephine sold for USD $48.4 million at Sotheby’s Geneva after being purchased by Hong Kong businessman Joseph Lau for his daughter.

All of these record-breaking stones shared the coveted Fancy Vivid Blue grade, helping explain their extraordinary per-carat values. While the Azure Blue surpasses them all in physical size, its Fancy Blue classification places it within a different rarity category. By contrast, the 5.04-carat marquise sits within the same elite colour tier as those historic diamonds, reinforcing the significance of its estimate.

Christie’s continues to play a leading role in presenting some of the world’s most important natural coloured diamonds to market. According to Claibourne Poindexter, Head of Jewelry Americas at Christie’s, “With its striking color, exceptional size, and elegant shape, The Azure Blue is a rare masterpiece of nature.”

The appearance of both the Azure Blue and a highly significant Fancy Vivid Blue diamond within the same sale positions the June 9 Magnificent Jewels auction as one of the most important blue diamond auction events in recent years.