Researchers of the Tairus joint venture have developed the technology for the hydrothermal growth of gem-quality crystals of synthetic sapphire. They have achieved a broad spectrum of attractive colors by varying the concentrations of Ni2+, Ni3+, and Cr3+. Comprehensive testing of 18 faceted synthetic sapphires and 10 synthetic crystals, representing the range of colors, revealed a typical set of internal features that are specific to hydrothermally grown crystals (microscopy), as well as the presence of OH- and various carbon-oxygen groups in the sapphire structure (infrared spectroscopy). The reactions of the test samples to ultraviolet radiation and visible light were also found to be useful in distinguishing the Tairus synthetic sapphires from their natural counterparts and other synthetics.

Appears on pages 188-202

Photo GIA and Tino Hammid