gems, bery, beryl, emerald, inclusions, Brazil, Santa Teerezinha de Goiás

The Santa Terezinha de Goias emerald deposit, currently the most important source of emeralds in Brazil, lies northwest of Brasilia, in the State uf Goias. The emeralds, most of which are stones of a carat or Jess, occm in a talc schist layer intersected by pegmatite. The emeralds are recovered by independent miners via trenches, pits, and tunnels at two prospects: Trecho Novo and Trecho Velho. The grade of the ore is: l to 6 parts of emeralds to 10,000 parts of ore. The density of the gems is 2.70; the refrnctive indexes are 1.580 and 1.588, with greenish dark blue/yellowish pale green pleochroism. The spectrum is typical, with two strong lines and two partial absorption bands; there is no fluorescence; pyrite and chromite are the most typical inclusions, with calcite crystals present in minor amounts.

gems, beryl, emerald, Australia, inclusions

Documents the history, geology, gemmological properties, and inclusions of emerald from the Emerald Mine near Emmaville, northern New South Wales, identified as Australia’s first commercial emerald deposit. D.A. Porter discovered green beryl in 1890 while examining an abandoned cassiterite lode, and T.W.E. David judged its colour sufficient to warrant the name emerald. A historical chronology traces successive mining campaigns, closures, renewed exploration, and the clearing of the workings in 1981. Early production was constrained by the small proportion of gem-quality material, generally pale colour, difficult extraction from hard host rock, and disappointing financial returns. Recorded production of 53,225 carats is considered incomplete. The emerald-bearing lode is an irregular quartz–topaz–feldspar–mica pegmatite derived from the nearby Late Permian Moule Granite and intruding Permian metasedimentary rocks. Emeralds occur in clusters within flattened cavities, commonly associated with dickite formed through hydrothermal alteration, as well as penetrating quartz, fluorite, topaz, and host rock. Associated minerals include cassiterite, arsenopyrite, and wolframite. Crystals are characteristically slender and hexagonal, usually small, with rare lengths approaching 3 cm. Colours range from faint green to bright light emerald green with a yellowish secondary hue. Earlier spectrographic analyses recorded approximately 1,000 ppm vanadium, 450 ppm copper, and 350 ppm chromium, with no detected iron; the green colour was attributed chiefly to vanadium, possibly assisted by copper. Representative specimens had refractive indices of 1.570–1.575, birefringence of 0.005, specific gravity of 2.68, negative uniaxial optical character, and yellowish-green to green pleochroism. They appeared very pale pink through the Chelsea filter, were non-fluorescent, and showed a broad absorption band centred near 610 nm with general absorption below 454 nm. Microscopy revealed two-phase tubes and dagger-shaped inclusions parallel to the c-axis, irregular fluid cavities occasionally containing three phases, partly healed basal cleavages, net-like veils, and randomly oriented healed fractures. Solid inclusions included fluorite, cassiterite, an unidentified silvery-white mineral, and later mineral fillings in cracks and resorbed cavities. These observations broadly confirmed an earlier inclusion study and supported a late-stage granitic, pneumatolytic origin. Brown argues that the green beryl should be classified as emerald despite its relatively low chromium content. Its low refractive indices and specific gravity are consistent with vanadium-rich emerald of moderate water and alkali content, although further analytical confirmation is required.

corundum, ruby, sapphire, treatments.6, inclusions.5, color.4, gems

corundum, ruby, treatments.6, inclusions, gems

Gunawardene discusses the identification of heat-treated and diffusion-treated ruby, with particular attention to treatment practices observed in Thailand and Sri Lanka. High-temperature heating can modify ruby colour and clarity, while diffusion treatment introduces colouring agents into a shallow surface layer. The paper describes conventional gemmological and microscopic features useful for recognizing treatment, while emphasizing that heat treatment alone may in some cases leave insufficient evidence for unequivocal identification. Diffusion treatment is generally more readily detected from the distribution of colour, particularly concentrations associated with the stone’s surface and facet geometry. The author also describes practical aspects of the treatment processes and discusses the problems such treatments pose for identification and the gem trade.

synthetic corundum.7, synthetic ruby, Kashan, flux, gems

Burch describes three visually distinct inclusion types in a single flux-grown Kashan synthetic ruby and proposes that their contrasting appearances may reflect different states of trapped residual flux. The investigation is based on microscopic observation and photography, without chemical analyses undertaken by the author, and is explicitly intended for comparative study rather than as a general identification guide for all Kashan rubies. Type I inclusions are conspicuous, opaque bodies with strongly reflecting, apparently metallic surfaces. Larger examples have irregular outlines, while smaller ones may be elliptical, rod-like, or spherical. Their apparent colours vary with illumination, and one contains a dark oval feature resembling a bubble. Burch interprets these inclusions as coarse crystalline flux residues; separately communicated analytical information indicates a high zinc content, suggesting an unusual flux composition or additive. Although potentially useful indicators of synthetic growth, such coarse inclusions were reportedly uncommon or absent in then-current faceted production. Type II inclusions are generally elongated and well formed, with angular terminations and a dazzling white, granular or crazed outer coating. Gaps in this coating expose a homogeneous transparent interior occupying most of each inclusion. Features that resemble bubbles at first sight may therefore be openings in the opaque coating rather than actual gas bubbles. Type III inclusions form fingerprint-like patterns superficially resembling those in natural ruby. Under higher magnification, they resolve into numerous tiny rounded or nearly spherical bodies, occasionally dumbbell-shaped, most appearing transparent and two-phase. Attempts to move their apparent bubbles were unsuccessful, suggesting, without proving, that the surrounding transparent phase is solid rather than liquid. Drawing an analogy with documented inclusions in Nacken synthetic emerald, Burch proposes that these fingerprints may contain glassy flux with small shrinkage bubbles. Rapid cooling could prevent crystallization of residual flux droplets, leaving a vitreous phase containing dissolved alumina and chromium. The intermediate-sized Type II inclusions might combine crystalline flux coatings with transparent flux-glass interiors, although their precise development remains uncertain. Inclusion size, cooling rate, and dissolved alumina content are proposed as factors determining whether trapped flux crystallizes or solidifies as glass. The three categories may therefore represent related products of the same growth system rather than unrelated inclusion materials. Burch concludes that all could consist essentially of solid flux in crystalline or vitreous form, with no apparent evidence for a liquid phase in the inclusions examined. The observations emphasize the need to distinguish visual resemblance to natural fluid inclusions from demonstrated phase composition.

corundum, sapphire, India.12, Kashmir, inclusions.5, geology.11, gems

The unique beauty of gem sapphires from Kashmir has brought fame to a locality about which little has been reported in recent years. After an initial burst of activity 100 years ago, the production of these gemstones has slowed to a trickle and the majority of the corundum from these mines today is of industrial grade. Despite evidence of other gem mineral occurrences i n the area, difficult terrain and political factors have impeded their exploitation. This article, the result of an expedition to the deposits in 1981, chronicles the history of the Kashmir mines, describes the characteristics of the sapphires found there, and examines the outlook for the future of this area.