Large 12-rayed black star sapphire from Sri Lanka with asterism caused by ilmenite inclusions
(2017) The Journal of Gemmology — Vol. 35, n° 5, p. 430-435 (2017)
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- Abstract
- A large (112.64 ct) black star sapphire of probable Sri Lankan origin that exhibits 12-rayed asterism was studied for this report. As in other 12-rayed star sapphires, its phenomenal appearance is due to the presence of oriented needle-like inclusions that produce two superimposed six-rayed stars that are rotated 30° relative to one another. However, Raman spectroscopy combined with optical microscopy unexpectedly revealed that the inclusions responsible for both stars consist of the same mineral, ilmenite. By contrast, 12-rayed star sapphires from Thailand typically contain separate inclusion sets of rutile and hematite-ilmenite series minerals corresponding to the two six-rayed stars.
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Citations
Bui, T. N., Entremont, P., & Gauthier, J.-P. (2017). Large 12-rayed black star sapphire from Sri Lanka with asterism caused by ilmenite inclusions. The Journal of Gemmology, 35(5), 430-435. https://doi.org/10.15506/jog.2017.35.5.430 (Original work published 2017)