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GIA Reports Heat Treated Spinels

August 29th, 2010 Leave a comment Go to comments

Barbra over at Gemologyonline made a post recently that reminded me a an important article that I forgot to post about, so here it is, better late then never!

This spring, the New York laboratory examined a 17.02 ct reddish orange spinel that contained a few small expansion halos or “blebs” emanating from strings of minute inclusions. The appearance of the inclusions suggested the stone was of natural origin — but may have been heat treated.

Read entire GIA Article HERE.

An excellent PDF article from GIA on the research results:

http://www.gia.edu/research-resources/news-from-research/Heated%20spinel%20Identification%20at%20April%2002%202009.pdf

Good news is, it appears that ID’ing heated spinel, at least chromium bearing varieties, is fairly easy due to the heat treatment apparently causing the chromium related emission peaks, normally very sharp, to become broad bands instead. Looks for these bands at around 676, 687, 698, 708, and 717 nm range using room-temperature photoluminescence (PL) spectroscopy. The treatment reportedly does NOT effect the color, only the clarity. The GIA PDF contains much more detailed information and is a must download and read!!

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