In this negative crystal within an untreated Sri Lanka padparadscha, one can see a high-relief hexagonal plate of graphite, along with a needle of diaspore. The undamaged nature of the negative crystal and diaspore needle confirms that the gem has not been heat treated.
Natural Padparadscha Sapphire • Sri Lanka (Ceylon) • Enhancements: None Detected (None) • Lighting Conditions: Fiber Optic: Overhead
Photographer: Richard W. Hughes •
Image Number: A-003-3562-2 • Date Posted: 22 May 2019
Koivula, J.I. (1980) Carbon dioxide as a fluid inclusion. Gems & Gemology, Vol. 16, No. 12, pp. 386–390; RWHL*.
Hughes, R.W., Manorotkul, W. et al. (2017) Ruby & Sapphire: A Gemologist's Guide. Bangkok, Lotus Publishing, 816 pp.; RWHL*.