Choudhary G. & Golecha C. (2007) An unusual YAG with a “reverse” colour change, Gems & Gemology, Vol. 43, No. 4, pp 387 -388

An YAG with a colour change effect was enclountered. In daylight, the sample appeared yellow, with some tinges of orange, while in daylight-equivalent fluorescent light, it appeared pinkish and in incandescent light, it appeared yellow. As such, this YAG showed a “reverse” effect, since color-change stones generally appear pink or red in incandescent light. This type of color change has been referred to as type 2, and is commonly seen in manufactured glasses, and, rarely, some other gems. This YAG was also interesting for its inclusions, which included complex patterns of etch channels, gas bubbles and angular zoning

Choudhary G. & Khan M. (2007) A remarkably large fire opal carving, Gems & Gemology, Vol. 43, No. 3, pp 258 – 259

We had the opportunity to examine and test an unusually large specimen of semitransparent brownish orange fire opal, which did not show play-of-color. This 492 g (2,460 ct) carving was fashioned after Lord Mahaveera. Examination with a microscope and fiber-optic illumination revealed some milky zones composed of fine pinpoint inclusions. These zones gave a slight haze to the carving, although this was visible only with strong lighting. As the fiber-optic light was moved around the specimen, the milky zones appeared to radiate outward from the center. Milky zones or clouds are commonly encountered in opals, but the radiating pattern has not been documented previously to our knowledge. The carving documented in the present entry was exceptional due to its large size combined with its attractive color and transparency

Choudhary G. & Golecha C. (2007) A study of nail-head spicule inclusions in natural gemstones, Gems & Gemology, Vol. 43, No. 3, pp 228 - 235

Nail-head spicules have traditionally been associated with Synthetic Hydrothermal materials mainly quartz and emerald. Rapid growth conditions and disturbances is the primary reason for their formation. However, there are instances when these or similar looking inclusions have been formed in natural gemstone and this article is a compilation of such stones which includes natural emerald, sapphire, spine, diamond and rock crystal. Natural emerald and natural sapphire presented has the “true” Nail-head spicules whereas in natural spinel, natural diamond and natural rock crystal have similar appearing inclusions due to abundant etch channels; crystals with stress and aggregation of crystals respectively. Nail-head spicule now remains a feature of rapid and disturbed growth and does not confirm the natural or synthetic origin without further examination.

Choudhary G. & Golecha C. (2007) Some convincing glasses, Gems & Jewellery, Vol. 16, No. 3, pp 6 -8

A constant development in technique and manufacture of synthetic gemstones and glasses often leads to products which may surprise a gemmologist. Rough glasses imitating emeralds, phenomenal glasses like colour-change, cat’s-eye, etc, have appeared over the years. Following descriptions in Gems & Jewellery (Mercer 2006; Miller, 2006; Millington, 2006) of some rough ‘gem’ materials simulated by lower grade materials like quartz, synthetic products or otherwise, we give details of some particularly convincing glasses recently submitted to the Gem Testing Laboratory of Jaipur. Each stone described here was interesting for its misleading features of visual appearance or inclusions similar to natural gems.