When a yellow sapphire is immersed in a yellow liquid like methylene iodide, it is difficult to see the growth zoning. Placement of a blue filter under the immersion cell provides the necessary contrast to easily spot features such as the curved color banding seen here, which proves this stone to be a Verneuil synthetic.
Synthetic Sapphire • Verneuil • Enhancements: None Detected (None) • Lighting Conditions: Diffuse Light Field + Immersion + Blue Filter
Photographer: Richard W. Hughes •
Image Number: R-001-4926-2 • Date Posted: 29 February 2016
Hughes, R.W. (1988) Identifying yellow sapphires—two important techniques. Journal of Gemmology, Vol. 21, No. 1, pp. 23-25, RWHL*.
Hughes, R.W. and Koivula, J. (2005) Dangerous curves: Verneuil synthetic corundum. Bangkok, Lotus Gemology; RWHL.