corundum, ruby, Burma.12, Thailand.12, origin determination, chemistry.2, gems

Examines the potential of proton-induced X-ray emission (PIXE) analysis to distinguish Burmese from Thai rubies through their trace-element compositions, supplementing identification by color and inclusions. Sixty specimens were studied: 29 purchased as Burmese rubies in Thai wholesale markets and 31 obtained from cutters in Chanthaburi and initially regarded as Thai. Microscopic examination supported the proposed origins of 57 specimens, while three lacked diagnostic inclusions. Measurements employed 2 MeV protons from a Van de Graaff accelerator at the National University of Singapore, a silicon-lithium detector and a counting time of 150 seconds per specimen. Samples required only cleaning and mounting. X-ray spectra were processed using the AXIL least-squares fitting program, and calibration standards prepared in an aluminum oxide matrix allowed concentrations to be expressed as weight percentages relative to Al₂O₃. More than ten trace elements were detected, with chromium and iron producing prominent signals; other constituents included silicon, sulfur, chlorine, potassium, calcium, titanium, vanadium, manganese and gallium. Vanadium and iron provided the clearest distinction between the two groups. All initially identified Burmese specimens displayed detectable vanadium peaks, whereas all but one presumed Thai specimen contained very little vanadium. The exceptional specimen also had the lowest iron concentration among the presumed Thai stones and lacked diagnostic inclusions. Its Burmese-like composition led the authors to reassign it provisionally to the Burmese group, producing final groups of 30 specimens each. Average vanadium concentrations were approximately 0.048% in the Burmese group and 0.002% in the Thai group, while average iron concentrations were approximately 0.122% and 0.444%, respectively. Burmese rubies also had higher average concentrations of the other tabulated impurities, although substantial variation occurred within each group. A plot combining vanadium and iron concentrations separated the studied populations more effectively than either visual color assessment or iron content alone. The authors present these compositional relationships as preliminary criteria, emphasizing that additional specimens are needed to establish reliable boundaries and confidence levels. PIXE offers simultaneous multielement measurement, sensitivity at parts-per-million levels for many elements, and analysis without conductive coating, stringent surface preparation or induced radioactivity. Its principal limitation is shallow sampling: the technique measures surface layers rather than the stone’s interior, and near-surface inclusions may distort concentrations interpreted as representative of the ruby itself.

corundum, sapphire, treatments.6, coated, gems

With the proliferation of diffusion treatment, heat treatment, and the filling of cavities in corundum, the laboratory is particularly diligent when examining rubies and sap-phires for enhancement.

corundum, sapphire, treatments.6, coatings, Sri Lanka.12, gems

corundum, synthetic corundum.7, synthetic star sapphire, Verneuil, gems

corundum, ruby, Vietnam, gems

gems, inclusions, beryl, emerald, Australia, Norway

The second installment of Schwarz’s systematic study of the chemical properties of emeralds from different geographic sources, dealing with material from Australia and Norway. Norwegian specimens are from Eidsvoll near Lake Mjøsa, while the Australian material represents several occurrences, including Pilangoora, Wodgina, Calvert White Quartz Hill, Warda Warra, Melville, Torrington, Emmaville and Menzies. Chemical analyses are used to compare major and trace-element compositions and to evaluate variations among deposits and against previously studied Brazilian emeralds. Schwarz notes, among other distinctions, generally lower magnesium contents than in Brazilian material. The paper demonstrates the usefulness of chemical composition, considered together with gemological properties, for characterizing emeralds and assessing their geographic origin.

gems, corundum, treatments.4, titanium diffusion, sapphire, bulk diffusion

This trade commentary defends the commercial introduction of surface [bulk] diffusion-treated Sri Lankan sapphires and questions the distinction drawn by some dealers between this process and conventional heat treatment. Lumetta describes an improved technique, developed in the United States from earlier Linde diffusion technology, that reportedly increases the penetration of colour into corundum. The resulting stones combine attractive blue colour, calibrated dimensions and good cutting, qualities that the author regards as difficult to obtain together in ordinary Sri Lankan production. Drawing on published accounts of corundum colour and enhancement, the article explains blue colour through iron–titanium charge transfer and describes treatment by heating stones in contact with colouring compounds so that titanium enters their surface layers. The author contrasts this addition of colouring elements with heat-treatment processes that modify existing constituents or their oxidation states, arguing that both approaches enhance appearance and that commercial opposition to diffusion reflects unequal access to technology and competing financial interests. This equivalence is presented as the author’s position rather than demonstrated through experimental comparisons. Surface diffusion-treated stones are placed between lower-priced synthetic corundum and more expensive Sri Lankan sapphires whose colour is natural or improved by conventional heating. Lumetta considers better-quality Thai sapphires their principal price competitors, with colour preference influencing purchasing decisions. He rejects predictions that the new product will depress sapphire prices generally and instead suggests that independently certificated fine sapphires may gain value through clearer differentiation. Disclosure is central to the argument: earlier diffusion-treated stones had sometimes circulated without identification, whereas the products discussed are explicitly marketed as treated material. The author acknowledges his involvement in their marketing through Gem Source in Las Vegas, where stones are offered in calibrated sizes, several cutting styles and graded colour categories. Their intended customers include larger jewellery manufacturers requiring a consistent supply of matching stones. The article predicts consumer acceptance on the basis of colour, cutting and price, presenting diffusion-treated natural sapphire as a distinct commercial alternative whose place in the market depends on transparent description and product differentiation.

inclusions, photomicrography, gems

Two colour photomicrographs document an unusual thin-film inclusion in a 462 ct aquamarine crystal from Pakistan. Published under the subtitle “An Aquamarine Adventure”, the brief contribution combines the photographs with the author’s account of changes observed during gentle heating and subsequent cooling. The inclusion is described as apparently containing two immiscible liquids, one of which has a syrupy appearance. When the specimen is gently heated, this liquid disappears into a dark portion of the inclusion; as the aquamarine cools, it reappears as slowly moving droplets. The photographs show different configurations of the internal liquid features within a brightly coloured, irregularly bounded film. Yellow and orange areas dominate the central field, with green, blue and violet colours towards its margins, while dark elongated features interrupt the illuminated region. Rounded and extended droplet-like forms differ between the two views, illustrating the changing appearance that accompanies the author’s observations. On the basis of its response at approximately 32 °C, the author suggests that one liquid is probably liquid carbon dioxide. This identification is explicitly tentative: the note provides an observational interpretation rather than a chemically confirmed analysis of the trapped fluids. It does not identify the second liquid or establish the geological conditions under which the inclusion formed. The photographic procedure was adapted to record the changing features. Although the author normally used professional Ektachrome 160 Tungsten film for photomicrography, Ektar 1000 print film was selected for these images because its higher speed was needed to arrest movement. The contribution therefore records both the visual character of a colourful aquamarine inclusion and the practical challenge of photographing mobile internal phases. Its principal evidence consists of the paired images and the reported reversible behaviour during warming and cooling, rather than a detailed experimental or compositional investigation. Together, these observations present an example of dynamic fluid behaviour within a gemstone and demonstrate how photomicrography can preserve successive appearances of an inclusion that changes during examination.

corundum, history.1, ruby, sapphire, Sri Lanka.12, gems

Carl Peter Thunberg’s eighteenth-century account of the gemstones of Ceylon, now Sri Lanka, is reassessed as an early contribution to scientific gemmology. A biographical sketch places the Swedish physician and naturalist within the intellectual tradition of Linnaeus and outlines his travels, collecting activities, and later academic career. Earlier descriptions of the island’s gem wealth, particularly those of Marco Polo and Jean-Baptiste Tavernier, provide historical context and illustrate the difficulty of interpreting old gemstone names. Thunberg acquired much of his information during a stay at Matara, where medical duties afforded opportunities for local excursions and the purchase of rough and cut stones. His observations include the role of Muslim lapidaries and the export of locally fashioned gems to India. Drawing on his travel narrative and related publications, Sinkankas reviews four non-gem minerals and twenty gemstone entries, recording historical names in several languages and comparing descriptions with modern mineral identities. Colour, crystal form, hardness, transparency, and alluvial wear provide the principal evidence for confirming or revising the identifications. Several stones described as ruby or as differently coloured tourmalines are interpreted as probable zircon, while other identifications remain uncertain because their descriptions are insufficient or contradictory. The discussion distinguishes rock crystal, milky quartz, citrine, smoky quartz, grossular garnet, and probable schorl, and identifies Thunberg’s “pseudo-opal” cat’s-eye as chatoyant quartz rather than chrysoberyl. Particular attention is given to colourless zircon sold as Matara diamond. Thunberg’s account of heating stones, then enveloping them in fine lime and firing them with rice chaff, constitutes early documentation of gemstone treatment intended to improve colour and clarity. The article also examines the limitations of eighteenth-century analytical methods. Assistance from Torbern Olof Bergman did not eliminate identification errors, whereas Martin Heinrich Klaproth’s improved chemical procedures helped establish the compositions and distinctions of corundum and zircon. Tourmaline’s electrical properties and the inconsistent application of its name receive separate consideration. Later observations by John Davy and other writers demonstrate the persistence of misleading trade terminology. The study presents Thunberg’s collection and descriptions as historically important evidence while emphasizing that early gem names require critical interpretation rather than direct equivalence with modern species.

corundum, history.1, India.12, gems, Indian lapidary