Choudhary G. (2008) An interesting zoned sapphire crystal from Winza, Tanzania, Gems & Gemology, Vol. 44, No.3, pp 270-272

We had an opportunity to characterize a 2.82 ct sapphire crystal that was purchased in Winza, Tanzania. It showed the crystal habit typically associated with sapphires. The most interesting feature of the crystal was its colour zoning. The area nearest the pinacoid was purple-pink, which gradually shifted to colourless and then blue. The latter colour increased from light to deep blue to almost black toward the lower end of the crystal, making it appear opaque. When magnified, this colour distribution seemed to be restricted to zones with sharp edges that mostly followed the pyramidal faces of the crystal. When the crystal was viewed along the c-axis, we observed a transparent purple-pink core that was surrounded by a dark blue to black rim

Choudhary G. & Bhandari R. (2008) A new type of synthetic fire opal: Mexifire, Gems & Gemology, Vol. 44, No.3, pp 228 - 233

Opals have been synthesized and imitated to be used in jewellery items for more than three decades, (Smallwood, 2003). This article describes the properties of a new type of synthetic fire opal marketed as “Mexifire.” Some of the gemological properties of this synthetic are similar to those of a natural fire opal. However, a low SG value (<1.77) offers strong evidence of synthetic origin, and further indications are provided by a relatively low RI value (<1.40) and the presence of scattered pinpoints when examined with magnification.

Choudhary G. (2008) Innovative composites ‘Fusion’, Gems & Jewellery, Vol. 17, No. 2, pp 20- 22

At the Gem Testing Laboratory, Jaipur, the author had the chance to examine some composites, which are being marketed as ‘Fusion’. These rather eye-catching composites are not made simply to imitate a well-known gem or to mislead consumers but to provide something innovative, fresh and fancy. Various materials used to make these composites include different colours or varieties of quartz and blue topaz. This review is presented in the form of a visual guide rather than a detailed analysis.

Choudhary G. (2008) A sapphire with en echelon inclusions, Gems & Gemology, Vol. 44, No. 2, pp 180-181

An 11.31 ct light violetish blue mixed-cut oval sapphire was seen.  There was no reaction to long- or short-wave UV radiation, and no absorptions were seen with the desk-model spectroscope. When examined with magnification, the stone displayed some linear whitish zones of dotted inclusions, which are commonly associated with natural sapphire (heated or unheated). At higher magnification, these zones appeared to be composed of fine white pinpoints arranged in an en echelon pattern. We could not determine the exact orientation of these linear zones relative to the c axis, but the optic axis was inclined to the planes containing these features. Hence, we can only speculate that the dotted inclusions were oriented along the dipyramidal faces of the crystal.