corundum, treatments.6, gems

A beautiful orangy yellow oval mixed-cut stone weighing 7.60 ct was submitted to the Santa Monica laboratory for identification. The refractive index, birefringence, and optic figure proved that the stone is sapphire. Microscopic examina-tion revealed natural inclusions as well as the strain discs, very fine dot-like silk," and round cotton-like inclusions that are indicative of heat treatment. Exposure to short-waveultravio-let radiation revealed three zones of chalky blue fluorescence close to the girdle, another sign of heat treat-ment. When the stone was immersed in methylene iodide, some interest-ing structural characteristics be-came visible. In addition to the straight angular yellow color zoning alternating with near-colorless areas, which is characteristic of natural origin, three straight blue zones close to the girdle (coinciding with the areas of chalky blue fluores cence] were seen. Figure 10 showo these blue areas, which could be the result of the heat treatment."

gems, early lapidaries, early gemology, early mineralogy, Albertus Magnus, Thomas of Hales, pearl

Medieval verse lapidaries tend to follow a traditional structure and often employ fixed formulas, beginning each entry with the name of the stone, followed by descriptions of its color and aesthetic qualities, then its supposed medicinal or magical virtues, and sometimes concluding with religious significance or a note on the ideal setting—typically gold—and a declaration of its princely worth, often emphasizing its exotic origin in the Orient. All these elements appear in Pearl: “Perle, plesaunte to prynces paye / To clanly clos in golde so clere, / Oute of oryent, I hardyly saye, / Ne proued I neuer her precios pere.” I have demonstrated elsewhere how poets take these formulas and develop complex conceits that are woven throughout their poems. This article focuses on three additional examples of poetic exploitation of lapidary formulas: A Luve Ron by Thomas of Hales, the secular love-lyric “A Wayle Whyt ase Whalles Bon” from MS BL Harley 2253, and the first of Henryson’s Fables, where recognizing the use of these conventions proves particularly fruitful in addressing a critical issue debated by several scholars.

gems, early lapidaries, early gemology, early mineralogy

Féry-Hue examines a previously little-studied version of the medieval French Lapidaire chrétien en vers preserved in Paris, Bibliothèque nationale, nouvelles acquisitions françaises 11678. The manuscript, copied in the second half of the fifteenth century, contains the lapidary on fols. 1–68v; its beginning is defective because the first leaf has been lost. By comparing its text with the eight other known manuscripts of the Lapidaire chrétien, Féry-Hue demonstrates that it represents a substantially reworked and expanded recension, rather than an independent lapidary. She analyzes alterations to the traditional sequence and descriptions of stones and identifies interpolated material drawn from other medieval encyclopedic and lapidary traditions. The study therefore adds an important ninth witness to the manuscript tradition and illustrates how medieval lapidaries continued to be reorganized and augmented during transmission.

gems, archaeology, archaeogemology, Africa, Libya

The part of Africa to be studied lies between the Middle Niger basin and the central valley of the Nile. It stretches from Sansanding in the west to Khartoum in the east, running across modern Mali, Niger, Chad, and Sudan, including the northern parts of Burkina Faso and Nigeria. Today, it is a region of little rainfall. Stretching down to the Sudan savannah in the south, its northern area is predominantly the Sahel and the desert. There are indications, however, that early in the first millennium of our era, it received more rainfall, and such locations as Kumbi, the metropolis of the ancient kingdom of Ghana, Timbuktu, and the Chad basin lay well within the Sudan savannah. As far north as Tibesti, the vegetation was luxuriant enough for camel herding and possibly for raising other large animals, such as donkeys, horses, and cattle. And so, the present Saharan part up to the latitude of Tibesti, Ténéré, and Aïr would have been of the Sahelian type. The discussion below will deal with that open region at a time when it was covered by grass and shrubs which made contact easier than it is today.

gems, turquoise, turquoise identification, turquoise imitation, dyed magnesite

Magnesite dyed blue to imitate turquoise has appeared on the market, including necklaces made from tumbled nodules sourced from Africa. This imitation can be identified by spot refractive index readings of 1.51 and 1.70, with the high birefringence indicating a carbonate. Its specific gravity, around 3.0, is higher than that of calcite or dolomite, both commonly used as turquoise simulants. Once identified as magnesite, the artificial nature of the coloration becomes clear, as blue magnesite does not occur in nature. Additionally, the recessed matrix areas in these nodules are filled with a wax-based black substance—likely added during polishing—to mimic the appearance of spiderweb turquoise.

gems, diamond, coated diamond

Gemmologists who grade diamonds should be aware of unusual features that I noted recently while examining four diamonds. The four stones, set into two different rings, were in the estate of an elderly woman who had worn the rings constantly for over fifty years while she lived in Deland, Florida. One diamond of 1.82 ct was set as a solitaire, and the other three stones, 1.23 ct, 1.53 ct, and 1.25 ct (all weights estimated by Leveridge method), were set side-by-side into the second ring. The first unusual feature of these stones was that they all fluoresced a brownish-yellow under short-wave ultraviolet light. The large solitaire showed a strong brownish-yellow fluorescence, while in the second ring the stones showed approximately the same brownish-yellow fluorescence although less intense. Another unusual feature of the stones was that they showed evidence of a coating even though they had been thoroughly cleaned in a professional ultrasonic unit. At first I supposed that the coating had been nefariously applied, but then realized that it was too haphazardly placed for that to be the case and was most probably accidental. The coating looked like water spotting that had dried in a somewhat scalloped design around many of the facet junctions. Additionally, the coating in all cases covered the table completely.

gems, ancient gems, glyptic, archaeology, archaeogemology, beads, chalcedony, technology, treatment, archaeological, South Asia, Indus Valley, Mohenjo-Daro, Chanhu-Daro, Harappa, stone drills modern use of double diamond drill bit in Khambhat, agate, carnelian, steatite, turquoise, jasper, serpentine (?), green aventurine

Archaeology and the study of ancient peoples have long been captivating fields, evolving from early treasure-hunting and collecting ventures into a more scientific investigation of cultural development and change. Recent research into the Indus Civilization, along with its Neolithic and Early Chalcolithic predecessors in the Indus Valley and Baluchistan, is uncovering new dimensions of human culture in South Asia. While the Indus Civilization has been renowned for its beads—traded as far as Mesopotamia—only now are scholars beginning to unravel the intricate techniques behind their production and the socio-economic organization of the industry that created them.

jade, nephrite, China, Xinjiang, Khotan, gems

Xinjiang’s Gems and Jades (新疆宝石和玉石), by Yang Hanchen, Yi Xianrui, Yi Shuangting, Song Jianzhong, and Min Yaoming, is a comprehensive Chinese-language study of the gemstones and ornamental stones of Xinjiang, combining mineralogy, gemology, geological occurrence, historical exploitation, lapidary technology, and economic evaluation. Originally published in 1986, the work was subsequently revised and expanded; the supplied 2012 edition incorporates additional research, photographs, analytical data, and information about newly identified deposits. The authors begin with a historical survey of gemstone and jade exploitation in Xinjiang, tracing the use of ornamental stones from prehistoric times through successive Chinese dynasties and examining the longstanding importance of Hetian nephrite in Chinese material culture. Particular attention is given to the distinction between traditional Chinese classifications of yu and modern mineralogical terminology, with comparative chemical analyses of ancient and contemporary jade materials. The book then establishes a classification of gemstones and ornamental stones before examining individual mineral species and gem varieties. The gemstone chapters cover beryl, including aquamarine, heliodor, and green beryl; tourmaline in its various colours; garnet, including grossular and the material marketed as Altai emerald; corundum; spodumene; apatite; topaz; feldspar, including amazonite; diamond; diopside; scapolite; and sphene. For each material, the authors discuss crystal morphology, colour, transparency, refractive indices, specific gravity, chemical composition, optical properties, suitable cutting methods, quality requirements, and geological occurrence. Numerous tables provide quantitative chemical analyses, while absorption spectra, infrared spectra, X-ray diffraction data, and photographs of rough and fashioned specimens illustrate diagnostic characteristics. The extensive ornamental-stone section places particular emphasis on nephrite from the Kunlun Mountains and associated districts, examining white, greenish-white, green, black, yellow, and variegated varieties. The authors investigate the chemical composition and microstructure of nephrite, including its fibrous amphibole aggregates, characteristic textures, mineral inclusions, colour variations, and physical properties. Detailed comparisons are made between nephrite from Hetian, the Kunlun Mountains, and other Chinese and foreign localities, supported by chemical analyses, microscopic photographs, and infrared spectra. Geological discussions describe the formation of nephrite deposits through metamorphic and metasomatic processes, particularly reactions involving carbonate rocks and intrusive bodies. Additional ornamental materials include serpentinite, quartz, rock crystal, agate, chalcedony, jasper, turquoise, lilac-coloured ornamental stone, wax-yellow stone, and several locally named varieties whose commercial terminology does not necessarily correspond to internationally recognized mineral species. The sections on agate illustrate numerous patterns, including banded, onyx, lace, and dendritic varieties, while those on turquoise examine chemical composition, colour, texture, and geological occurrence. Historical illustrations of Chinese jade carvings complement technical discussions of cutting, polishing, grading, and craftsmanship. The concluding chapter classifies gemstone and ornamental-stone deposits according to their geological origins, describes the relationships between mineralization and host rocks, and identifies prospective areas for exploration throughout Xinjiang. The book is especially valuable for its regional geological observations, mineralogical analyses, locality information, and detailed treatment of nephrite, providing an important Chinese-language reference for researchers investigating Central Asian gem deposits, the history of the Chinese jade trade, and the scientific identification of Xinjiang’s ornamental stones.

gems, topaz, Pakistan

In addition to the relatively recent discovery of significant amounts of emerald, aquamarine, and ruby, Pakistan has also begun to produce fine gem-quality pink topaz. In a small hillock of recrystallized limestone north of Katlang, narrow calcite veins encase pink topaz crystals up to 3 cm long, accompanied by larger amounts of reddish brown, tan, and colorless topaz crystals. More than 70,000 ct of gem-quality pink topaz has been reported to date. The refractive indices, optic axial angle, unit-cell dimensions, and density of the topaz are influenced by a partial replacement of fluorine by hydroxyl ions. The color is due to trace elements—principally chromium (Cr³⁺). Treatment experiments revealed that the color of the brown, tan, and colorless topaz from this source may be improved by irradiation and heat.

corundum, sapphire, treatments.6, surface repair, glass infilling, Nigeria.12, Montana.12, gems

A glass filling in a faceted sapphire is investigated by electron microprobe analysis and compared with previously analysed glasses in ruby to assess whether it formed naturally or through treatment. The principal specimen is a 1.28 ct round mixed-cut sapphire with a known history extending back to 1979. A surface-reaching glassy area near the culet measures less than 1 mm across and contains numerous bubbles. Such fillings can be detected by careful examination in reflected light or by immersion, which helps reveal small bubble-bearing areas. Ten analyses give a mean composition of 57.5 wt% silica, 29.4 wt% alumina and 6.7 wt% sodium oxide, with smaller amounts of iron, calcium, potassium and magnesium oxides. Although individual analyses vary, the composition broadly resembles that of a previously studied ruby filling, with differences particularly in sodium, potassium and calcium contents. Three possible origins are considered: natural volcanic glass adhering to corundum, artificial glass introduced during treatment, and glass produced by melting pre-existing mineral inclusions. A volcanic origin is geologically conceivable because sapphires occur in basaltic deposits and may undergo corrosion during transport in magma. However, the filling differs substantially from typical alkali basalt and from reported residual volcanic glasses, especially in its high alumina content. Available experimental data do not permit every possible natural glass composition to be excluded. Treatment materials, including coatings, pastes and crucibles, could supply the elements needed to form artificial glass. Element maps show an essentially homogeneous filling and a sharp boundary against the sapphire, without an aluminium gradient supporting dissolution of the host as the source of alumina. The high melting temperature and viscosity expected for such glass nevertheless make it an unusual choice for intentional filling. No known mineral closely matches the filling’s sodium–aluminium–silicon proportions. Heating experiments on jadeite at 1200–1600 °C show insufficient sodium loss to explain the difference by volatilisation during melting. The authors conclude that the glass in the examined sapphire is artificial. More generally, glass fillings in corundum have varied compositions: some may derive from melted natural inclusions, whereas others are more plausibly associated with artificial treatment.