The iron-rich Australian sapphires are predominantly blue (90%), with some yellow, some green, and a very few parti-colored stones. The rough stones are commonly heat treated in Thailand to remove the ...

Leeawatanasuk et al., “Cobalt-doped glass-filled sapphire; an update,” The Australian Gemmologist, Vol. 25, No. 1, 2013, pp. 14–20). Recently examined at the Carlsbad laboratory was a particularly ...