Lot 423. Exceptional 11.70 carats Type IIa diamond ring, JAR. Estimate 950,000 — 1,550,000 CHF. Lot Sold 1,202,500 CHF. Photo Sotheby's

Claw-set with a round-cornered rectangular modified brilliant-cut diamond weighing 11.70 carats, to a mount set with single-cut stones, mounted in platinum, signed JAR Paris, French assay and maker's marks. size 52 ½,

Accompanied by GIA report no. 17229568 and Gübelin report no. 0808340, stating that the diamond is D Colour, VS2 Clarity.

Together with a Gübelin note and appendix to report no. 0808340 respectively stating that the diamond is a Type IIa stone. 

Notes: 'Golconda' is a name steeped in the annals of diamond lore. The name of a now ruined fortress which originally served as a commercial trading centre, some days distant from the historic Indian mines of Ramalakota, Kollur and Soumelpour. The term 'Golconda' has now survived to describe the historic diamonds peculiar to India of great limpidity and purity. These diamonds are from the famed 'First water' mines, which produced the world's most spectacular diamonds, such as The Koh-I-Noor, The Hope and The Agra. This beautiful stone, with its appealing antique cut, is a member of the rare Type IIa group of diamonds known for their extreme purity, qualities compared so often throughout history to pure crystallized water. Scientifically this purity is due to the absence of nitrogen, producing stones often said to be beyond white.

In our opinion, this present gemstone is probably part of the highly desirable group of surviving diamonds which were mined in the Golconda region up to the beginning of the XVIIIth century.

Widely acknowledged as being the most talented jeweller of his generation, JAR was established on the Place Vendôme in Paris in 1977 by Joël Arthur Rosenthal, better known by his trade name JAR. Born in New York City, Rosenthal studied art history at Harvard University, later working in the film industry and then with Bulgari. Drawing upon the past, but allowing his natural creativity to dominate, he has reinterpreted jewellery as an art form, crossing the boundaries between ornamental jewels and sculpture. JAR's work is always imaginative and beautifully crafted and often incorporates unusual gemstones in brilliant and unexpected combinations.  A 10th anniversary celebration exhibition was held in New York in 1987 and a larger highly glamorous retrospective of 400 jewels was on show at The Gilbert Collection, Somerset House in London in 2002.

Sotheby's. Magnificent Jewels, Geneva, 19 Nov 2008