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A rectangular-cut emerald and diamond ring

The rectangular-cut emerald weighing 15.57 carats with triangular-shaped diamond shoulders, mounted in 18k gold and platinum, ring size 6¼. Estimate CHF310,000 - CHF430,000 ($280,635 - $389,269 - Price Realized CHF327,000 ($296,025)

Accompanied by report no. 52629 dated 09 October 2008 from the SSEF Swiss Gemmological Institute stating that the emerald is of Colombian origin, with no indications of clarity modification

Notes: For many years it has been recognised as an acceptable practice to lessen the appearance of natural inclusions in emeralds with oils and resins. Indeed, today it is almost universally recognised that most - up to 99 of - emeralds will have some level of treatment, judged by the amount of oil or resin used. Minor treatment is already a greatly desirable attribute for a gem emerald, but to find gems of the highest quality without any sign of treatment - as completely natural as the earth intended, excepting the cutting and polishing of the lapidary - is unusual. Moreover, in the case of stones over 10, and certainly 15 carats, of such a clean material and uniformly pleasing colour as the emerald being offered here, the purity of such a gem-quality crystal is particularly noteworthy.

Christie's. jewels : The Geneva Sale. 13 May 2009. Geneva www.christies.com