Unstable Colouration of Padparadscha-like Sapphires

• Published in: Journal of gemmology (1986) Vol. 36; no. 4; pp. 346 - 354
• Main Authors: Krzemnicki, Michael S., Klumb, Alexander, Braun, Judith
• Format: Journal Article
• Language: English
• Published: London The Gemmological Association of Great Britain 2018
• Subjects: Color; Precious stones; Madagascar
• ISSN: 1355-4565; 2632-1718
• DOI: 10.15506/JoG.2018.36.4.346

After the October 2016 discovery of a new gem deposit at Bemainty near Ambaton-drazaka, Madagascar, a number of sapphires with padparadscha-like colour entered the trade. However, most of these stones were found to have unstable colour, which changes from pinkish orange to more-or-less pure pink after a few weeks in daylight. In this study, the authors investigate the colour stability of padparadscha-type sapphires of metamorphic origin—mainly those originating from Madagascar (Ambatondrazaka and Ilakaka) and Sri Lanka. The 48 samples could be separated into three groups after colour-stability testing: sapphires that did not show a noticeably different appearance (case A); sapphires with a slight-to-moderate colour difference within the padparadscha range (case B); and fancy-colour sapphires showing a distinct change in appearance that fell outside of the padparadscha range (case C). The last situation was especially common for the stones from Ambatondrazaka, thus revealing that careful colour-stability testing is mandatory for proper gemmological identification of any sapphire showing a yellow to orange colour component.