Please note the following statement regarding coloured stones:
Regarding Coloured Stones
Prospective buyers are reminded that many coloured gemstones have historically been treated to enhance their appearance. Certain enhancement methods, such as heating, are commonly use to enhance both colour and transparency, particularly in rubies and sapphires. Other methods, such as oiling, enhance the clarity of emeralds. These methods have been generally accepted by the international jewelry trade. Although heat enhancement of colour is widely believed to be permanent, it may have some impact on the durability of the gemstone and special care of the stone may be required over time. For example, gemstones that have been oiled may require re-oiling after a period of years to retain their maximum appearance.
It is Christie's policy to obtain gemological reports from internationally recognized gemological laboratories describing certain gemstones sold by Christie's. The availability of such reports will be disclosed in the catalogue. Reports from American gemological laboratories used by Christie's will disclose any heat enhancement or treatment. European gemological laboratories will disclose heat enhancement only if specifically requested but will confirm when no heat enhancement or treatment has been made. Because of variations in approach and technology there may not be consensus among laboratories as to whether any particular gemstone has been treated, the extent of the treatment and whether treatment is permanent.
It is not feasible for Christie's to obtain a gemological report for each gemstone offered by Christie's. Prospective buyers should be aware that all gemstones may have been enhanced by some method. For further details, prospective buyers in the United States are referred to the information chart prepared by the Gemmological Standards Commission, available in the viewing area. Prospective buyers may request laboratory reports for any uncertified items if requests are made at least three weeks before the scheduled day of auction. This service is subject to prepayment by the requesting party.
Because enhancement affects market value, Christie's estimates will reflect the information disclosed in a report or, if no report is available, the assumption that gemstones may have been enhanced.