corundum, treatments.6, gems

The history of glass-infilling in blue sapphire is reviewed, along with a detailed description of the latest generation of this treatment, which was developed by Tanusorn Lethaisong in Chanthaburi, Thailand. Stones may be identified by reference to their inclusions, lack of pleochroism and red reaction in the Chelsea filter. Spectra and other advanced tests further characterize and separate these stones from natural and synthetic sapphire, as well as heated and bulk diffused sapphire.

China, Tibet, andesine, feldspar, diffusion treatment, gems

Analysis of Tibetan andesines collected by Richard Hughes and Dana Schorr in Tibet. Fluid inclusions with no heat damage demonstrate that there is natural red andesine in Tibet.

corundum, inclusions.5, photomicrography, gems

A gemologist’s life would be far easier if gems were cut as parallel-sided plates. But they’re not. Facets are designed to reflect light back to the viewer, not transmit it. This means light entering the gemstone from behind (transmitted light) will typically not pass straight through. If we want to see inclusions, we must constantly change the light paths through the gemstone. This is done by changing the position of the gemstone relative to the light and changing the light relative to the gem. The most versatile and controllable method of doing this is with the fiber-optic light, an illumination technique “darker” than even darkfield. During a recent routine identification of a natural chrysoberyl a startling difference in two distinctly different types of illumination commonly used in the examination of gemstones was clearly revealed. These two methods are darkfield and fiber-optic illumination. When this chrysoberyl was studied in darkfield (Figure 1), only a fine linear growth band was seen. However, when fiber-optic lighting was directed in along the girdle plane, bundles of fine light-scattering silky needles extending at 90˚ from the linear growth band became abundantly clear. At the same time the linear growth band itself was also more clearly detailed (Figure 2). The difference in the amount of visual information provided by these two different lighting techniques was startling. In this instance darkfield was clearly inferior to fiber-optic illumination.

corundum, inclusions.5, gems

A discussion of how inclusion patterns mimic crystallographic symmetry in ruby and sapphire.

corundum, ruby, Vietnam.12, inclusions.5, gems

Discussion of the appearance in Thailand of large quantities of ruby from northern Vietnam.

corundum, India.12, Kashmir.11, Burma.12, gems

No gemologist today would deny the importance of inclusions to the study of gemology. They are vital tools in separating synthetic gems from natural, and their importance will certainly increase along with the growing sophistication of treated gems. However, the question of inclusion-based country-of-origin reports does not find all gemologists and traders in agreement. Some support the practice; others do not. The following article takes a close look at the entire question of lab-issued origin reports, asking… a. are origin reports accurate within a reasonable degree of error using the current methods? b. even if origin reports are reasonably accurate, how are they being used in today's market? Do they provide useful collector information and protection to prospective customers, or are they merely a diversion for drawing the buyer's attention away from the stone's overall appearance and quality, to some ill-definable factor, such as origin? c. are origin reports akin to the authentication of a painting by a master artist, or do natural gems have only one artist Mother Nature? The purpose of this article is, thus, to explore objectively the arguments for and against lab origin reports. First the author explains why he believes origin reports are not totally reliable and definitely not in the best interests of the consumer. Supporters are then given the opportunity for rebuttal, explaining why they think Mr. Hughes has lost his mind. It is our hope that, out of the fray, readers, defenders of the faith, and opponents will better understand this question of origin.

corundum, sapphire, East Africa, Kenya.12, inclusions.5, gems

A brief inclusion study was done on a small sampling of Turkana sapphires provided by Ted Themelis. Perhaps the most distinctive feature throughout the lot of approximately 30 pieces was a slight cloudiness, or girasol," if you will. While in reflected light the stone might appear blue or green, in transmitted light an oily yellowish "diesel" appearance was seen (see Figure 1). This was found in virtually all specimens, except the one piece which had been heat treated. Heat treatment removed this cloudiness, as well as improving the color, suggesting that the cloudiness may be exsolved Ti and/or Fe compounds."

gems, quartz, agate, chalcedony, inclusions, history

This superb volume is perhaps the best of all the extraLapis English series, which is saying a lot. Gossamer ribbons swirling with color and light, agate has a universal appeal. Unconstrained by any internal architecture: agate is a freeform expression of its ancestral fluids, which organize into complex patterns that echo the voids it fills. The effect is natural, balanced asymmetry — a wabi sabi, Zen aesthetic — which is perhaps what compels us to hold it as a memento, metaphor, talisman, curiosity, microcosm, or charm. Humans have interacted with agate since time immemorial; and although it minutely details the conditions under which it formed, agate has been the focus of relatively few studies — its code has yet to be cracked. Agate thus remains an enigmatic gemstone — a kaleidoscope of complex textures birthed of simple, common silica — that inspires a wide swath of people from to children to naturopaths to artists, scientists, and collectors. With articles on the history, art, science, and vocabulary of agates, our expert team of authors explore the niche between science and art occupied by this fascinating gem. Extraordinary imagery illuminates the story, enticing readers to get to know the irresistible Quartz Phenomenon — Agate.

corundum, ruby, sapphire, history.1, chemistry.2, properties.3, geology.11, inclusions.5, sources.12, synthetic corundum.7, treatments.6, assembled stones.8, color.4, fashioning.9, quality.10, introduction.0, bibliography, books on books, jade, jadeite, fei cui, nephrite, gems

It is difficult to overstate the importance of this two-volume work, which was the product not just of John’s writing career, but also of his home business, Peri Lithon, which he operated for decades with his wife, Marge. No authors ever worked harder on a single work. Over 6,000 entries, virtually all of which are annotated. There is a limited edition in fake leather with a siipcase. My pick for the greatest gem book of all time.

gems, corundum, treatments.4, Sri Lanka.12, Madagascar.12, heat treatment, FTIR

This study examines sapphires naturally enriched in high-field-strength elements (HFSE) from metamorphic origins in Sri Lanka and Madagascar. These sapphires display distinctive chemical inhomogeneities and microscopic growth features, as well as variable FTIR spectra, often including a broad absorption band near 3300 cm–1. Some of the studied samples also show FTIR spectral characteristics and short-wave UV luminescence typically associated with heat-treated stones, although all were unheated. Our findings demonstrate that commonly used indicators—such as specific FTIR band patterns (mainly the 3309 cm–1 triplet) and chalky bluish white short-wave UV fluorescence—are not always reliable for identifying heat treatment. Accurate distinction between heated and unheated sapphires requires detailed microscopic examination combined with advanced trace-element analysis and spectroscopic techniques, including Raman micro-spectroscopy of inclusions such as zircon, goethite and diaspore.