Ottu Sapphire and Diamond Ring
Lot Closed
November 14, 12:50 PM GMT
Estimate
10,000 - 20,000 CHF
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Read more.Lot Details
Description
Set with a cushion-shaped sapphire within a old European-cut diamond border.
- Sapphire weighing 7.91 carats
- Size 53
- Accompanied by GGTL report no. 25-G-31326, dated 18 June 2025, stating that the sapphire is of Ceylon origin, with no indications of heating and no indication of colour modification, together with a side letter; further accompanied by a gemmological report, an insurance valuation and two original documents dating to the 1930s
- 1930s
- Gross weight approximately 4 grams
Clara Allirol-Mouton, Franck Notari and Féodor Blumentritt, Un Remarquable Saphir 'Ottu' au Laboratoire, in Gemmes, la revue de l'Association Gemmologie & Francophonie, 2025, no. 6, pp. 11 - 21, for a research paper which has this sapphire as its subject.
'This sapphire is described as a blue and colourless gemstone as a result of its uneven colour distribution. Naturally showing a significant colour zoning, the blue hue is only located in a thin layer from the crown to the table. The rest of the gemstone is colourless with a slightly yellow hue. As the colour gradation is appreciated with the stone seen through the table, its overall distribution produces a relatively even blue colour in that orientation. The colour of the gemstone is thereby graded as deep blue, leading to the identification of this gemstone as sapphire on the report. Gemstones featuring such thin layers of colour are known as 'Ottu sapphires' in Sri Lanka.'
Excerpt from the GGTL Side Letter
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