synthetic beryl, emerald, natural beryl, emerald, gems

Electron-microprobe analysis is investigated as an additional means of distinguishing natural from synthetic emerald when conventional gemmological properties and internal features are inconclusive. Refractive indices, birefringence, specific gravity and fluorescence can overlap, while inclusions and growth structures may be absent or difficult to interpret. The study therefore examines differences in minor-element chemistry, contrasting the relatively near-ideal beryl composition of many synthetic emeralds with the greater chemical substitution commonly found in natural material. Forty-five faceted stones from different natural sources and synthetic manufacturers were examined, with four point analyses performed on each specimen. Magnesium and sodium provide the clearest separation within the investigated population. Natural emeralds contained at least approximately 0.8 wt% MgO, with most values between 1.5 and 3.0 wt%, whereas synthetic specimens commonly contained around 0.1 wt% and reached approximately 0.4 wt%. Natural stones contained at least 0.4 wt% Na₂O, while most synthetic stones had no measurable sodium; the highest reported synthetic value was 0.2 wt% in a Lechleitner sandwich product. Chromium and iron concentrations overlap between the groups and consequently do not provide a general diagnostic separation. Compositional variations among natural emeralds also show patterns associated with different geographic sources, with Colombian specimens tending to contain fewer impurities than most other natural samples. A Brazilian stone labelled as emerald from Conquista contained vanadium and iron but no detectable chromium, illustrating the variability of the colouring constituents. Additional observations include 0.3–0.4 wt% chlorine in Linde hydrothermal synthetic emeralds and exceptionally high chromium concentrations in Lechleitner synthetic emerald overgrowths. The author relates the characteristic network of fissures in these coatings to lattice-dimensional differences caused by chromium substituting for aluminium. Electron-microprobe analysis is presented as a means of obtaining diagnostic chemical information from cut stones without destructive sampling. However, the author explicitly recognizes that 45 stones cannot represent the full compositional range of either natural or synthetic emerald. The magnesium–sodium distinction is therefore proposed as a useful supplementary criterion requiring broader testing, including examination of new synthetic products. Water content and additional trace elements are identified as potentially valuable future discriminants.

corundum, inclusions.5, gems

Pinpoint illumination uses a highly flexible but extremely durable glass fiber-optic bundle that incorporates six easily interchangeable light wands of various shapes and cross-sectional thicknesses down to one millimeter in diameter. The wands are hand held and can be used to illuminate hard-to-reach areas in complex jewelry ino~intingsW. ith the pinpoint, ill~lmintaor, a gemstone can be examined from any angle; the light source is placed exactly where it is needed, minimizing glare and unwanted external or internal reflections.

corundum, treatments.6, gems

A natural sapphire of unusual color came into the New York lab for identification. The brilliant orange-yellow seemed unnatural, and the lack of fluorescence and absence of an iron line in the absorption spectrum strongly suggested a heat-treated stone. The clincher, however, was an unpolished burned area near the multiplane girdle (figure 13). Figure 14 shows yet another example of incomplete repolishing of a heat-treated orangy yellow natural sapphire. It came from a lot of six stones, all of which clearly owed their color to heat treatment. One yellow sapphire from another lot of four stones recently seen in New York faded appreciably after exposure to south daylight for a day or so. Normally, we would assume that the color was due to irradiation and not to heat, but we recently heard that certain heat-treated yellow natural sapphires may fade (Gems & Gemology, Spring 1982, pp. 47–48). This has not yet been confirmed.

corundum, USA.12, Montana.12, gems

jade, jadeite, fei cui, dyed jade, identification, gems

The separation of naturally colored lavender jadeite from color-treated material is a problem that has long plagued gemologists. One theory is that the dying agents being used are of an organic nature. If this is true, they should break down at elevated temperatures and lose their coloring ability. Naturally colored lavender jadeite, however, should retain its color and not bleach on heating. T o investigate this theory, the author sawed 42 different specimens of lavender jadeite in half. One half of each specimen was heated while the other half was retained as a color control. Those stones that bleached on heating showed a strong orange fluorescence to long-wave ultraviolet radiation before heating and a moderate bluish-purple X-ray fluorescence both before and after heating. The control halves of those stones that retained their color when heated to as high as 1000°C fluoresced a very weak brownish red when exposed to long-wave ultraviolet radiation and a strong reddish purple to pink when exposed to X-ray radiation both before and after heating.

gems, jade, pyroxene jade, fei cui, guatemala, Mesoamerica, Nicaragua, Mexico, Honduras, Costa Rica, archaeogemology, Mayan design, aesthetics, Olmec, Aztec, Guatemala, archaeology, lapidary, Teotihuacan, obsidian, natural glass

Obsidian production was a major component of Classic period Teotihuacan's economy, with hundreds of workshops producing cores and blades of green obsidian and bifaces of grey obsidian for distribution throughout central Mexico. Although green obsidian was evidently obtained through a state network, grey obsidian procurement was conducted independently by most workshop groups. Most production took place in residential areas beyond the major public structures of the city, but some of these craftsmen also worked periodically within the public precincts where their output would have been at the disposition of state officials. The burden of this levy fell primarily upon those sectors of the industry that were most dependent on the state for support and most involved in external distribution. However, despite this evidence of an important administered element in the Teotihuacan obsidian industry, the workshops apparently maintained their independence from the state. This may have been due to their organization in strong social units that had a long history of independent existence, and to their self-reliance in procurement and distribution during the earlier stages of the industry's development.

gems, jade, pyroxene jade, fei cui, Guatemala, Mesoamerica, Nicaragua, Mexico, Honduras, Costa Rica, archaeogemology, Cuba, Dominican Republic, Olmec, Mayan, Aztec, Mixtec, Toltec, Zapotec

The Dumbarton Oaks Conference on the Olmec, held in late October 1967, was pervaded by the generous and gentle spirit of the “grandfather of Olmec studies,” Matthew Stirling. It was my first conference on a Pre-Columbian theme and my first sight of the great man. He and his wife, Marion Stirling, invited the participants and those associated with Dumbarton Oaks to their home for dinner on Saturday night. It was there that I found myself sitting at the feet of all of the North American archaeologists who had been present at the actual excavation of the great Offering 4 at La Venta—the famous group of thirteen stone figures and six halved celts arranged as a ritual group. They described how it all had to be recorded, photographed and removed in the same day for fear that it might be stolen that night. Robert Heizer told how the next day they were able to pinpoint exactly the balancing offering, which appeared to be wizardry to the laborers. But the most moving part of that conference was Matthew Stirling, the man who had excavated all the important Olmec sites and had unerringly called attention to most of what we still know about that mysterious civilization. His love affair with the Olmec sites began with a blue-jade masquette in the Berlin Museum which he had gone to see in 1920. What attracted Matthew Stirling and all olmecistas from José Melgar through Miguel Covarrubias to the present generation is the remarkable conception and mastery of form and technique in the working of materials—especially the working of hard stones such as jade and serpentine. It might be said that no other lithic culture in world history has been as precise in its choice of stones and as accomplished in the working of them as the Olmec. I would like to discuss Olmec forms and materials from the highlands of Mexico—especially north-central Guerrero.

gems, gem testing, gemology, advanced gemology, advanced testing

In 1948, Raymond Castaing, then a student of A. Guinier, presented to the University of Paris a doctoral thesis entitled “Application of Electron Beams to a Method of Local Chemical and Crystallographic Analysis.” The instrument he described had been produced by modifying an electron microscope, using an electron beam focused to a diameter of less than a micrometer (1 µm = 10⁻⁶ m) to excite X-rays within a microscopic region on the specimen surface. Spectral analysis of these X-rays provided information about the composition of the excited region, while the crystalline structure of the area could also be investigated using the Kossel-line X-ray diffraction technique. Castaing’s electron probe microanalyzer has since become the most important tool for elemental microanalysis, distinguished by its high spatial resolution, nondestructive operation, quantitative potential, wide elemental detection range, and compatibility with a variety of specimen types.

gems, topaz, irradiated topaz

A parcel of 100 deep blue irradiated topaz stones imported from Brazil was found to exhibit radioactivity levels slightly above natural background levels. Analysis revealed that the stones had been treated with neutrons in a nuclear reactor. While most irradiated topaz in the trade is not radioactive, this case highlights the importance of routine testing. For the safety of jewelers, it may be prudent to test not only topaz but also other gemstones such as beryl, green diamonds, and red tourmaline—and potentially all gemstones—for radioactivity.

gems, ancient gems, glyptic, archaeology, archaeogemology, ancient history, beads, India, Gujarat, Cambay, Indian lapidary

Cambay, a small city of about 50,000 people on the coast of Gujarat in western India—known in English as Cambay but originally called Khambhat—is renowned for its lapidary craftsmanship, with its products reaching markets across four continents. The most prominent of these crafts is bead-making, which is the focus of this discussion. This industry is far from new; it likely began as early as the third millennium B.C. with the founding of the Harappan settlement at Lothal, a site dating to approximately 2400–1700 B.C. Lothal featured a large-scale bead manufacturing operation that transformed raw materials such as chalcedony, agates, jasper, and rock crystal into beads used both locally and exported as far as Mesopotamia. Since that era, the Cambay region—if not the exact site of the ancient town—has remained a vital commercial hub, particularly known for the production and trade of beads and textiles. While the historical record is uneven, it is evident that Cambay has consistently played a key role in trade between India, Africa, Asia, and Europe. With this context in place, the discussion now turns to the bead manufacturing process itself.