Christie’s has announced the upcoming offering of the Ocean Dream, the largest known fancy vivid blue-green diamond in existence, at its prestigious Magnificent Jewels auction in Geneva in May 2026. The extraordinary gemstone is expected to achieve up to CHF 10 million (approximately USD 12.8 million).

Weighing 5.50 carats, the triangular-cut diamond is graded fancy vivid blue-green, SI1 clarity, and classified as a rare Type IIa stone. The gem is set in a ring featuring an intricate mount adorned with sculpted rock crystal, alongside round and pink diamonds, underscoring its exceptional craftsmanship and design.

Certified by the Gemological Institute of America, the Ocean Dream holds the distinction of being the largest vivid blue-green diamond ever graded by the institute. The polished gem originated from an 11.70-carat rough discovered in Central Africa, further enhancing its provenance and rarity.

This marks only the second time the Ocean Dream has been presented at auction. It was previously sold by Christie’s in Geneva in May 2014, achieving CHF 7.8 million (approximately USD 8.7 million at the time), and has since remained in a single private collection for over a decade.

The diamond’s legacy is further enriched by its inclusion in the renowned “Splendor of Diamonds” exhibition at the Smithsonian Institution National Museum of Natural History in 2003, where it was recognized as one of the world’s most exceptional diamonds.