Unusual Inclusions in Green Synthetic Sapphire
A 5.00 ct green square step cut (above left) was submitted as a synthetic sapphire to the laboratory of the State Gemmological Center of Ukraine. Standard gemological testing gave a refractive index of 1.763–1.768, with a uniaxial negative optic sign and a birefringence of 0.005, as well as a hydrostatic specific gravity of 3.94. The sample was inert to short- and long-wave UV radiation. Pleochroism was moderate green to yellowish green. Energy-dispersive X-ray fluorescence (EDXRF) spectroscopy showed only small amounts of Co (0.07 wt.% Co3O4). In the jewelry market, such synthetic green sapphires are quite rare. Microscopic examination revealed abundant gas bubbles, including some along curved lines. From these observations we can infer that the Verneuil or Czochralski method was used to create this stone. In addition to these bubbles, there were straight lines of bubbles in multiple directions (above right), which are extremely unusual in Verneuil- or Czochralski-grown synthetic sapphire.
