Certification is a must. The key is the knowledge that the stones are natural and, in the laboratory, show no signs of heat treatment.
Trevanion (22% buyer’s premium) found a fine early 20th century cabochon sapphire and diamond ring among a recently inherited collection of costume jewellery.
Trevanion’s jewellery specialist Helena Waudby said: “The lady thought that the entire contents was costume jewellery, and of little value. However, as we dug our way through piles of beads and bangles, we discovered quite a number of treasures. The owner had travelled extensively and had a fascinating range of pieces.”
The ring was looked at by Gemmological Certification Services, its report stating the natural 13.8ct oval cabochon sapphire was from Burma.
On February 15 in Whitchurch, Shropshire it sold for £15,000 (estimate £6000-10,000).
Two in Lichfield
Featuring in the Antiques & Home Sale at Richard Winterton in Lichfield on March 27 are two early 20th century sapphire jewels: a 4.16ct Burmese sapphire and diamond ring (estimate £5000-7000) and a pair of Burmese and Ceylon sapphire and diamond earrings, with stones totalling 5.60ct (guide £5000-7000). All the stones have been certified as natural by Anchor Cert.
Of the three key sources for blue sapphires (Burma, Kashmir and Sri Lanka), the last-mentioned is by far the most prolific producer. It is also the source of the biggest gems: late last year the Sri Lankan authorities put on show ‘the world's largest natural corundum blue sapphire’ weighing 310kg.
A lot of lower-grade material is available on the market (since the 1970s so-called geuda sapphires have been turned an attractive vivid blue through heat and chemicals) so a premium is to be paid for natural stones.
In the March 23 sale at Duke’s in Dorchester a white gold, sapphire and diamond pendant on offer comes with an Anchor Cert report stating that the central 14.91ct cushion cut stone of a strong violet blue has no evidence of treatment and was mined in Sri Lanka (Ceylon). It is estimated at £5000-10,000.
Also a Sri Lankan stone, a Georgian sapphire and diamond-set cluster ring was offered by Catherine Southon (24% buyer’s premium) as part of a good collection of Georgian and Victorian jewellery at the Farleigh Golf Course, Surrey, on February 8. With a central oval stone in a closed back silver and yellow gold setting (the 9ct gold shank was later), it made £13,000.