Choudhary G. (2010) And now composite chalcedony, Gems & Jewellery, Vol. 19, No. 4, pp 28 - 30

Gagan Choudhary reports on a very unusual composite submitted to the Gem Testing Laboratory of Jaipur. The composites were made from pieces of light to dark green and orange chalcedonies with silvery white and golden matrix; the matrix was basically a polymer containing fine flakes of silvery white and golden material. The specimens with the silvery white matrix also displayed a sheen effect similar to that which is observed in some shells

Bhandari R. & Choudhary G. (2010) Update on Mexifire synthetic fire opal, Gems & Gemology, Vol. 46, No. 4, pp 287 - 291

As a result of changes in the manufacturing process, recent production of the synthetic fire opal marketed as “Mexifire” exhibits some new properties. While the earlier material could be identified on the basis of low RI and SG values, the new synthetics have values that are quite similar to--and partially overlap those of-- natural fire opals. With the change in the manufacturing process, the water content has also changed, as reflected in the IR spectra. The RI and SG of these new "mexifire" opals is 1.470 and 2.19 as compared to 1.380 - 1.405 and 1.63 - 1.77respectively, for the older version.

Choudhary G. (2010) A strongly thermoluminescent spodumene, Gems & Gemology, Vol. 46, No. 4, pp 322 - 323

The Gem Testing Laboratory of Jaipur, India, recently examined a green spodumene that displayed a striking example of thermoluminescence. When the specimen was placed under the fibre optic lamp, it turned into bright orange within two to three minutes, however, it returned back to green within few minutes. These reactions were repeatable with consistent results. The orange glow was similar to the stone’s fluorescence reaction to long-wave UV radiation. This spodumene’s thermoluminescence at such a low temperature makes it an unusual specimen

Choudhary G. (2010) Glass with crystalline aggregates, Gems & Gemology, Vol. 46, No. 4, pp 328 -329

Glass is the most common gem simulant, and can show a wide variety of colours, transparencies, and optical effects.  The Gem Testing Laboratory of Jaipur, India, received a green 25.04 ct octagonal step cut specimen which had the translucency of chalcedony and the colour of emerald. Microscopic examination with fiber-optic light revealed aggregates of colourless crystalline features throughout the sample. The presence of these crystals initially suggested a natural origin. On the basis of gemmological properties and FTIR / EDXRF analysis, the specimen was identified as glass.  Such specimens make very convincing gem simulants. In the absence of proper gemological testing and FTIR/EDXRF analysis, there is a strong possibility of misidentification