Choudhary G. (2008) Purplish blue synthetic quartz, Gems & Gemology, Vol. 44, No. 4, pp 377 – 379

Synthetic quartz has long been available in a wide range of colours such as yellow, purple-violet, green, pink, colourless, parti-coloured, and even blue. The Gem Testing Laboratory of Jaipur, India, had an opportunity to study new and unusual “cobalt” blue synthetic quartz. At first glance, the specimen appeared to be a cobalt glass because of its colour and apparently frosted surface. With careful observation, however, we saw tiny circular growth features that were very similar to the “cobbled” surface seen in rough slabs of synthetic quartz. Examination with magnification confirmed the presence of a seed plate, colour zoning parallel to the seed plate, as well as nail-head spicules along its length. An interesting aspect was the location/orientation of the spicules. In general, nail-head spicules are oriented in one direction pointing away from the seed plate, on both sides of the synthetic overgrowth. In this case, however, most of the spicules appeared to be in the seed plate rather than in the overgrowth material. At some viewing angles, the spicules appeared to be oriented in different directions

Choudhary G. (2008) Multi-coloured synthetic quartz, Gems & Jewellery, Vol. 17, No. 3, pp 14-16

Two specimens of quartz represented as natural quartz from Pakistan were studied at the Gem Testing Laboratory of Jaipur, India. One of the specimens was multi-coloured with bands of green and yellow as its two main components, the pattern more often encountered in fluorites. The other was green with triangular patches of yellow. On magnification, the colour patches, in a view parallel to the table facet, appeared as zonal columns along the optic axis direction as indicated by the bull’s-eye optic figure.

Choudhary G. (2008) Two interesting synthetic rubies, Gems & Gemology, Vol. 44, No.3, pp 279 – 281

We encountered two synthetic rubies that were interesting because of their natural appearance. The rubies were purple-red mixed-cut ovals weighing 3.50 and 2.97 ct. The 3.50 ct sample appeared to be divided into two sections, one transparent and the other translucent. The transparent portion displayed a cloud of fine “pinpoints” in a radiating pattern; this cloud was further surrounded by a circular zone. The translucent portion contained a dense concentration of globular and tubular inclusions. When viewed in certain orientations, the inclusions were seen to be concentrated in parallel planes intersecting one another at angles that appeared to be 60°/120^o, similar to the orientation of rhombohedral planes. The 2.97 ct specimen had obvious surface breaks containing eye-visible orange stains, and also a milky zone towards the longer girdle end. The milky zones had curved edges and were composed of fine gas bubbles

Fernandes S. & Choudhary G. (2008) A tourmaline crystal within a crystal, Gems & Gemology, Vol. 44, No.3, pp 272 - 273

We had a chance to study an unusual 2.5 g tourmaline crystal that contained an intergrowth of a second, smaller tourmaline crystal. When observed with transmitted light, the stone’s unusual feature became evident: it contained an elongated crystal that was inclined to the length of main crystal. With magnification, the prismatic habit of the included crystal was seen to be remarkably uniform. It displayed a pyramidal termination and a triangular cross-section. Weak striations along the length of prism were also visible. A small part of the included crystal extended beyond the host crystal, and it displayed a green colour similar to that of the host. The surface features of the included crystal indicated variations in its growth conditions. We believe that it is “protogenetic,” meaning it formed before the main tourmaline crystal. After the smaller crystal formed, its prism faces were apparently etched by residual fluids, and subsequently it was overgrown by the host tourmaline crystal