Deepdene (diamond) - Irradiation Scandal

Irradiation Scandal

On 27 May 1971, Christie's auction house in Geneva offered to prospective buyers the cushion-cut, fancy golden-yellow diamond which would only later come to be known as the "Deepdene." Its clarity was stated as VVS1 (with two very small imperfections near the girdle or midsection of the stone) and its vivid-yellow colour was guaranteed to be natural by both the German gemological institute and the University of Mainz.

However, Dr. Eduard Gübelin, the founder of Gübelin Gem Lab in Lucerne, Switzerland, had the opportunity to inspect the diamond before the auction took place. Gübelin's experience with examining gemstones and recognizing artificially colored diamonds led him to declare that the Deepdene had been irradiated, likely by neutron bombardment. Gübelin warned Christie's and any buyers who would listen, but the sale was allowed to continue with the recommendation that the stone be examined by another lab.

After being sold to jewelers Van Cleef & Arpels for a reported £190,000 (about US$460,000 at the time), the Deepdene was sent to the Gem Testing Laboratory in London, England. The lab's director, gemological pioneer Basil Anderson, was given the task of substantiating Gübelin's claims. That he did, using spectral analysis, with damning results. Van Cleef & Arpels promptly returned the stone for a refund, leaving it somewhat of an unwanted orphan. Its current whereabouts remain uncertain.

Assuming Winston did not have the irradiation treatment done, it could have taken place any time between 1955 (when Winston sold it) and 1971, the year it was offered at auction. The recutting of the gem from 104.88 carats (20.98 g) to 104.52 carats (20.90 g) was most likely intended to remove the 'umbrella' coloration pattern it had around its culet. This was a common side effect seen in early irradiated diamonds but irradiation technique has been improved upon so that it no longer occurs.