Choudhary G. (2012) Dioptase from Mozambique, The Australian Gemmologist, Vol. 24, No.9, pp 215-219

One dark bluish green dioptase specimen weighing 8.88 carats was submitted to the Gem Testing Laboratory, Jaipur, India. The specimen was unusual for its size, crystal form, transparency and phantom-like growth. Dioptase, usually found as massive aggregates and druses on other minerals, was seen here as a single crystal of fairly good size. The specimen was reported to originate from Mozambique. IR spectra obtained by KBr method was very useful in the identification together with its gemmological properties. The specimen was dark bluish green, a colour typically associated with translucent emeralds exhibited under normal lighting/viewing conditions. However, under transmitted light, it displayed a much brighter green colour and a better degree of diaphaneity. IR spectra measured by KBr method displayed strikingly clear and distinct peaks in the region 4000 - 400cm^-1. Major peaks were seen at around 3380 and 3260 cm^-1 due to O-H vibrations; 1735, 1265, 1120, 993, 956, 887 and 781 cm^-1 due to Si-O stretching; 628, 572, 516, 495 and 450 cm^-1 due to Si-O bending

Choudhary G. (2012) A dyed blue opal with play-of-colour, Gems & Gemology, Vol. 48, No.1, pp 69-70

The laboratory received an unusual blue opal for identification. Its unusual colour and striking play-of-colour raised doubt regarding its authenticity. Presence of cellular structure (digit pattern) identified this opal as natural from Wollo, Ethiopia. However, the blue colour was not correct for an opal. With desk model spectroscope three bands at 540, 580 and 650 nm were seen, which are associated with cobalt and is often seen in dyed blue materials. Under Chelsea filter, the opal appeared strong red, confirming the presence of dye. Further microscopic examination revealed a surface break with blue colour concentrations.

Choudhary G. (2011) Quartz with acicular emerald inclusions, Gems & Gemology, Vol 47, No. 4, pp 323

The laboratory encountered a quartz specimen which displayed eye visible elongated emerald crystals present as inclusions similar to commonly seen rutile or tourmaline. The prominent green inclusions displayed hexagonal profile, consistent with emerald but their acicular / elongated habit raised some doubt. Spectroscopic properties concluded these as emeralds. Textural relationships indicated that the emerald crystals formed before the host quartz i.e. they are protogenetic

Choudhary G. (2011) Composite malachite plates, Gems & Jewellery, Vol. 20, No. 3, pp 3-5

The author reports on few plates composed of tiny fragments or pieces of malachite. These pieces were held together using a polymer based matrix. Identification of the fragments as malachite was not a problem as they displayed characteristic botryoidal banding with minute radiating crystals. In some areas, the botryoidal banding terminated at uneven boundaries. In between, some randomly oriented minute crystals were visible along with hemispherical pits. The composite nature of these plates was easily identifiable using a 10x loupe and a light source. Presence of gas bubbles along the junction planes within the cementing agent was readily visible all over the plate, although a careful observation was necessary