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Long P.V.,Center for Gems and Gold Research and Identification of Vietnam | Pardieu V.,GIAs Bangkok Laboratory | Giuliani G.,Institute of Research for Development in Toulouse
Gems and Gemology | Year: 2013

In 1987, gems were discovered in the Luc Yen area of Vietnam's Yen Bai province. Ruby, sapphire, and spinel from primary and secondary deposits are the most valuable of these; tourmaline, gem-quality feldspar, pargasite, and humite are also mined there. As a result of this discovery, the Luc Yen district has become Vietnam's most important gemstone-trading center over the past 30 years. The markets of Yen The, the capital of Luc Yen, offer an additional assortment of natural gems from Vietnam and elsewhere (including peridot, beryl, aquamarine, topaz, and quartz); synthetic gems are also found in these markets. © 2013 Gemological Institute of America. Source


Sturman N.,GIAs Bangkok Laboratory | Homkrajae A.,GIAs Bangkok Laboratory | Manustrong A.,GIAs Bangkok Laboratory | Somsa-Ard N.,GIAs Bangkok Laboratory
Gems and Gemology | Year: 2014

Pearls of all kinds have been used for decorative purposes throughout history. The majority of these have been nacreous, yet certain non-nacreous pearls have also been sought by connoisseurs. Pinna (pen) pearls fall into the latter group. The nature of their non-nacreous structure often results in cracking, and because of stability concerns they are very rarely used in jewelry. Nineteen of the 22 samples from this study, reportedly from Pinnidae family mollusks, show similarities in color as well as external and internal structure. Raman, photoluminescence, and UV-Vis-NIR spectroscopic results are discussed, along with the internal characteristics of pearls likely produced by this mollusk. © 2014 Gemological Institute of America. Source

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