Unstable Colouration of Padparadscha-like Sapphires

Author : Michael S. Krzemnicki, Alexander Klumb and Judith Braun

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 llakaka) 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.

Published Date : 04 Jul 2019
Page : 9
Publisher : Gemmological Association of Great Britain
Category : Geology & Gemology
Source : The Journal of gemmology : Vol.36 No.4 (2018), p.346-354
Available : Unlimited

MARC INFORMATION

020 a : ISBN 
1355-4565 
050 b : Published Year 
2018 
245 a : Title 
Unstable Colouration of Padparadscha-like Sapphires 
260 b : Name of publisher 
Gemmological Association of Great Britain 
300 a : Total pages 
520 a : Description 
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 llakaka) 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. 
650 a : Subject 

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