I have a gemstone mounted in a ring that was sold to me as a Tanzanian Zircon (unheated). It very much resembles a apricot-pink/brown tourmaline. How can I tell without dismounting the stone, if at all, what it is? I have already had it looked at and two out of three people seem to believe it is a tourmaline but I can't get anyone who has made a visual-only assessment (at various jewelry stores) to explain why it appears to be a Tourmaline aside from the color resemblance. To me it more resembles a so-called blush zircon but it also seems to color-shift under different light going from an orange-pink to purple-brown. I collect various color Zircon gemstones, hence the question.
Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
Hello and welcome! With access to gemological instruments the separation would be easy. Will the mounting allow you to take a refractive index? The refractive index for tourmaline is approximately 1.620-1.640, with a typical birefringence of 0.020 The RI for zircon is over the limit of the instrument.
A hand held spectroscope would also separate the two. Zircon has a diagnostic absorption line at 653.5 nm.
Zircon has an exceptionally high birefringence, so with a loupe you should be able to see profound doubling of the back facets or internal characteristics. Here's a pic I took of zircon some time ago:
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