gems, jade, archaic jade, archaeology, archaeogemology, jadeite, nephrite, omphacite, fei cui

A new framework for the consideration of Neolithic axes is proposed, consisting of six rock classes defined by rock composition and working properties. The use of rock from these classes varied systematically in Britain, and reflected local geology. Flint exploitation, whose significance in the production of axes has been grossly underestimated, is considered in especial detail (with a full survey of flint mines and quarries). A major study of axe morphology is reported on. The paper includes gazetteers of caches of stone axes (many previously unpublished) and of axes found in burials.

gems, advanced testing, analytical testing, chemistry, ruby, quartz, lapis lazuli, limestone, glass, feldspar, turquoise, malachite

Ion beam analysis has seldom been applied to gemmology. The privileged location of the Laboratoire de recherche des musées de France, close to some of the most prestigious art collections, along with the implementation of the AGLAE IBA facility, have allowed us to initiate several gemmological research programs since 1991. The latest of these deals with a series of Achaemenid jewels (IVth century BC) exhibited in the Louvre museum. The aim of the present research is three-fold: determination of the coloured materials inlayed in gold, composition of the golden alloys and the inlay fixation technique. Analyses have been carried out by PIXE using an external proton beam under conditions set from test experiments on reference gemstones in order to optimise the experimental parameters. Quantitative chemical analysis of both major and trace elements has allowed us to distinguish between 15 types of fine or ornamental stones as well as man-made materials and to identify a peculiar cement technique. We will describe the analytical procedure in detail, then present the main results obtained on coloured inlays and cement and underline a potential drawback of the technique, i.e. a transient colour variation of the target under the impact of the beam, which needs further investigation.

gems, tourmaline, Kenya

Tourmaline from a recent find in Kenya, referred to as “savannah” or “golden” tourmaline, has attracted attention for its distinctive coloration. Gemologist Yianni Melas submitted two rough samples for examination: a 4.50 ct transparent brownish orangy yellow piece with green areas, and a 3.06 ct crystal section showing a brownish orangy yellow core with a green rim. The broken crystal section displayed only prism faces, lacking striations parallel to the c-axis. Gemological properties recorded include pleochroism from brownish orange to yellow in the yellow regions and dark green to light yellowish green in the green areas, uniaxial optic character, refractive index of 1.630–1.650 with a birefringence of 0.020 (on the green rim), and specific gravity of 3.05. Under long-wave UV, the stones were inert, but showed moderately chalky yellow fluorescence under short-wave UV, stronger in the green rim. Spectroscopic analysis showed general absorption to ~480 nm, with additional bands between 590–630 nm and lines at 650 and 680 nm in the green rim. Inclusions observed included anhedral crystals, needles or tubes, two-phase inclusions, and hollow tubes. EDXRF spectroscopy revealed Mg, Al, Si, K, Ca, Ti, Fe, Zn, Ga, and Sr in both samples, with one showing a small Mn peak. Chromium was detected in the green rim, consistent with the observed color-filter and absorption data, indicating Cr as the chromophore for the green. Reported sources for this material include the Kasigau Mine in Tsavo West National Park, the Mangari area in the same park, and M’gama Ridge south of the Taita Hills in southeastern Kenya.

gems, glyptic, engraved gems, agate, cameo, intaglio, Rome, Roman gems, history of gemology

Features a chromian chalcedony carved head.

gems, ancient gems, glyptic, archaeology, archaeogemology, ancient history, Greek, Roman, Near East, India, Persia, Indian lapidary

During the Sasanian period (c. A.D. 224–651), the longstanding Near Eastern tradition of using stone seals and clay sealings persisted in notable abundance. A traveling Greek reportedly remarked, “Every Persian has his seal,” highlighting the ubiquity of this practice. Thousands of Sasanian seals have been documented, though only a small percentage come from controlled excavations, leaving aspects of their precise chronology unresolved. All published examples are stamp seals—typically dome- or ellipsoid-shaped and varying in size—with three additional forms noted: carved stone ring seals; flat, engraved stone bezels mounted in metal rings (brass, bronze, copper, silver, or gold); and rarer examples made from meteoritic iron. The engraved flat surfaces often bear inscriptions in Pahlavi, while some seals also feature curved decorative lines or facets on their outer edges, distinguishing them from earlier stamp seals. Professor Edith Porada described the Sasanian engraving style as heavily reliant on the mechanical drill, which produced globular forms. Lines of uniform width defined key features, contributing to the rounded, stylized look characteristic of Sasanian art across various media—from stone reliefs to silver vessels. The seals themselves show considerable variety, ranging from finely executed pieces to more hastily carved examples.

corundum, chemistry.2, gems

Growth-structure analysis has become increasingly important as a gemological tool for locality classification and distinguishing between natural and synthetic gemstones. This article presents the methods and instruments needed to analyze the internal growth structures of corundum. As an application of this testing procedure, the negative rhombohedral d (0112) plane is documented as part of the crystal habit in a small number of natural rubies—both as a subordinate form and, for the first time in natural rubies, as a dominant crystal form. Until recently, this crystal face was primarily associated with flux-grown synthetic rubies and sapphires.

corundum, Madagascar.12, Andranondambo, gems

Milisenda and Henn describe the geological setting, gemological properties, inclusions and chemical composition of blue sapphires from the newly commercialized Andranondambo occurrence in southeastern Madagascar. The deposit lies approximately 100 km north of Fort Dauphin, within altered marbles and calc-silicate gneisses of the Tranomaro formation. These rocks belong to a high-grade metamorphic terrain extensively reworked during the Pan-African event. Regional geochronological evidence leads the authors to infer that corundum formation accompanied granulite-facies metamorphism approximately 600 million years ago. Sapphires are recovered with simple hand tools from small pits in residual gravels, and the occurrence is considered promising for commercial development. Studied samples are slightly to moderately included and commonly display conspicuous colour zoning, with intense blue concentrated in broad central bands. Alternating darker and paler layers and growth structures follow basal and bipyramidal planes. Heat treatment can substantially reduce the visible zoning and improve appearance. Crystal fragments preserve rhombohedral and pyramidal forms consistent with metamorphic sources, contrasting with the etched or partly dissolved surfaces often associated with basalt-transported corundum. Refractive indices are 1.761–1.763 and 1.769–1.771, maximum birefringence is approximately 0.008, and specific gravity ranges from 3.91 to 3.98. Distinct to strong dichroism combines green-blue and violet-blue hues. All samples are inert under long-wave ultraviolet radiation; most are also inert under short-wave radiation, although weak greenish-blue or uneven orange fluorescence occurs occasionally. Polarized absorption spectra show ferric-iron features and iron–titanium intervalence charge transfer responsible for blue colour. The approximately 850 nm absorption commonly observed in sapphires from basaltic sources is absent. Preliminary microprobe work identifies apatite, calcite, dolomite and an incompletely characterized clay mineral among the inclusions. Other features include probable mica platelets, apatite associated with parallel hollow tubes, negative crystals, healed fractures containing fluid inclusions and occasional lamellar twinning. Electron microprobe analyses of three sapphires identify iron as the principal trace constituent, followed by titanium, with smaller measurable amounts of silicon, gallium and chromium. The combined evidence closely resembles that of metamorphic sapphires from Sri Lanka and Myanmar, supporting the classification of Andranondambo as a significant new source of metamorphic blue sapphire.

gems, gemology, gem identification, gem property tables, reference

The Gemological Institute of America’s Gem Reference Guide for the GIA Colored Stones Course, first published in 1995 and issued electronically in 2009, is an extensive illustrated reference designed to support the identification, grading, evaluation, and care of colored gemstones and related ornamental materials. Organized alphabetically by gem species, varieties, and commercial categories, the guide provides standardized information on natural gemstones, organic gem materials, synthetic stones, simulants, and assembled products. Each entry follows a consistent format covering chemical composition, crystal system, appearance, color range, transparency, optical properties, refractive index, birefringence, dispersion, pleochroism, ultraviolet fluorescence, absorption spectra, specific gravity, hardness, fracture, cleavage, characteristic inclusions, and crystal habit. Additional sections describe gemstone enhancements, diagnostic separations, durability, cleaning recommendations, commercial availability, geographic sources, and disclosure requirements. The introductory chapters explain GIA’s system for describing gemstone color through hue, tone, and saturation, supplemented by ColorMaster notations, and distinguish the different approaches required for grading transparent and translucent materials. Particularly useful are the numerous illustrated absorption spectra, crystal diagrams, gemstone photographs, and comparative identification tables that assist in separating visually similar materials. Corundum receives extensive treatment, with separate entries for ruby, blue sapphire, fancy sapphire, star ruby, star sapphire, and synthetic corundum. The guide documents diagnostic optical properties, typical inclusions, color mechanisms involving chromium, iron, and titanium, and the effects of heating, diffusion, irradiation, fracture filling, and other treatments. Ruby and sapphire deposits in Myanmar, Sri Lanka, Thailand, Cambodia, Australia, Kenya, Tanzania, and other countries are identified as important commercial sources. Emerald and other beryl varieties receive similarly detailed treatment, including characteristic inclusions, optical properties, geographic origins, oil impregnation, and the identification of synthetic emeralds produced by flux and hydrothermal methods. The garnet group is subdivided into almandine, andradite, grossular, hydrogrossular, malaia, pyrope, rhodolite, and spessartine, with particular attention to color variations, diagnostic spectra, and the separation of related species. Other substantial entries cover chrysoberyl, alexandrite, cat’s-eye chrysoberyl, spinel, tourmaline, topaz, zircon, quartz, opal, pearl, turquoise, and ornamental stones. The sections entitled “Jadeite Jade” and “Nephrite Jade” reflect the terminology employed by GIA in 1995. The former describes jadeite-bearing gem material, including commercially recognized color and quality varieties, while the latter concerns the felted tremolite–actinolite material known as nephrite. From a modern mineralogical standpoint, the jadeite-bearing gem rock is more appropriately termed fei cui, which may contain jadeite, omphacite, and kosmochlor in varying proportions. The guide also examines related ornamental materials such as maw-sit-sit, serpentine, hydrogrossular garnet, and saussurite, emphasizing their separation through refractive index, specific gravity, absorption spectra, and microscopic examination. Treatments discussed throughout the volume include heating, irradiation, dyeing, bleaching, impregnation, coating, diffusion, and fracture filling, with attention to treatment detection, stability, and consumer disclosure. Synthetic gemstones and diamond simulants are treated separately, including synthetic corundum, spinel, quartz, opal, emerald, cubic zirconia, synthetic rutile, YAG, and GGG. Organic materials such as amber, coral, ivory, shell, and natural and cultured pearls are also included. Although some nomenclature, locality information, treatment technology, and gemological interpretations have subsequently changed, the volume remains a useful historical reference for the identification practices, commercial terminology, and instructional standards employed by GIA during the mid-1990s.

gems, jade, jadeite, fei cui, Burma, assembled stones, treatments, B-jade, bleached and impregnated, dyed nephrite

JADEITE — Bleached and impregnated, with distinctive surface texture: The West Coast laboratory received for identification a 6.78-ct translucent, mottled-green cabochon that revealed properties typical for jadeite jade, with an R.I. of 1.66 (by the spot method) and an S.G. of 3.34. Chromium lines, seen with a spectroscope, proved that the green color was natural. The stone was inert to short-wave UV radiation, but some areas fluoresced a faint green to long-wave UV. The gemstone had an unusual, etched appearance in reflected light (figure 6): the aggregate structure of the cabochon appeared to be made up of many interlocking grains in various orientations, with certain grains preferentially eroded. Because of this surface texture, we suspected that the stone had been bleached and polymer impregnated. Infrared spectroscopy confirmed this treatment by revealing several peaks between 2800 and 3200 cm⁻¹; the relative positions and intensities of these peaks matched those of “polymer 5” in ICA (International Colored Gemstone Association) Laboratory Alert No. 75, 1993, issued by S. McClure and E. Fritsch. Therefore, we identified the stone as impregnated jadeite jade, natural green color, sometimes known in the trade as “B jade.” Interestingly, the S.G. of this stone was higher than that of most polymer-treated jadeites we have encountered thus far. JADEITE — Treated and untreated beads in one necklace: A comprehensive report on bleached and impregnated jadeite in the Fall 1992 Gems & Gemology (Fritsch et al., pp. 176–187) described features diagnostic of this treatment. The Lab Notes section has also reported on jade objects treated in this fashion, including entries on necklaces constructed of treated beads (see, e.g., Fall 1994, p. 187). Until recently, however, our testing had shown that all of the beads in these necklaces were treated. In November 1994, the West Coast lab was asked to identify a double-strand necklace with 69 beads (7.88–5.08 mm) on one strand and 74 beads (8.18–5.49 mm) on the other. Standard gemological testing proved that the translucent to semi-translucent, mottled green-and-white beads were jadeite jade. A desk-model prism spectroscope showed chrome lines, proving that the green color was natural. One unusual feature was noted during testing: some of the beads on both strands fluoresced a weak-to-moderate, mottled yellow to long-wave UV radiation, while others were inert. Most polymer-impregnated jadeite fluoresces. However, some untreated material may also fluoresce a weak yellow to long-wave UV. In our experience, we usually do not get such varied reactions from beads on one necklace. Further testing, using infrared spectroscopy, proved that there were treated (impregnated) and untreated beads in both strands. This was our first encounter with such mixed strands. Dyed green nephrite. Of the two jades (jadeite and nephrite), jadeite is much more commonly color enhanced (usually dyed green). Nevertheless, we occasionally find evidence of green dye in nephrite submitted for identification (see, e.g., Spring and Summer 1984 Gem Trade Lab Notes, pp. 48 and 108, respectively). In December 1994, the West Coast lab was asked to identify five oval, translucent, mottled-green cabochons, which ranged from 6.38 to 7.12 ct. All had an appearance similar to that of good-quality jadeite. However, standard gemological testing—including a 1.61 spot R.I. and an S.G. of 2.95 or 2.96—identified the five stones as nephrite. Magnification revealed dye concentrations (figure 7) like those seen in dyed jadeite and other similarly treated gem materials. The absorption spectrum observed with a desk-model prism spectroscope revealed a broad dye band in the red region, much like that seen in dyed-green jadeite and quartzite. In these stones, the diagnostic absorption band was centered at about 660 nm. All five specimens were therefore identified as dyed nephrite.

gems, archaeology, archaeogemology, Vietnam, beads, garnet, hessonite, grossular, almandine

Enam for the first time. While things were not quite so easy for the visitor as they are in much of Southeast Asia, they will certainly get easier now that a quarter century of isolation has been broken by American recognition of its government. My visits took me to four institutions where I saw and studied beads: the Institute of Archaeology and the History Museum in Hanoi, the History Museum in Ho Chi Minh City (HCMC; consisting of Saigon, Cholon and the surrounding area), and the Museum of Oc-Eo Culture in Tan An, Long An province, south of HCMC. I am especially grateful to Ian Glover, Institute of Archaeology, City College, London, who put me in touch with some of the people involved; Allison and Victor Diem of Manila, who made other recommendations; Nguyen Thi Kim Dung of the Institute of Archaeology, Hanoi; and the staff of the institutes I visited.