Chiang Mai Journal of Science

Trapiche patterns are common in emeralds but less common in corundum, and are typically restricted to ruby. Trapiche sapphire is  comparatively rare. Blue sapphires of  the trapiche type from southern Vietnam reveal a distinct core and fixed six-rayed star, similar in appearance to the patterns found in some rubies from Mong Hsu, Myanmar. The trapiche consists of  dark brown to brown core, six blue sectors separated by six brown to brownish yellow arms of  the star. Some samples also show a distinct colour zoning. A massive concentration of  needle-like inclusions is seen in the arms under the microscope. These are oriented perpendicular to the hexagonal crystal faces. A number of  inclusions are also observed in the core area. Gemmological, microscopic, spectroscopic, and chemical properties are presented to describe the characteristics of  the blue sapphires from southern Vietnam.