gems, beryl, emerald, India

In the mid-1990s, emeralds were discovered embedded in the wall of a well at the village of Sankari Taluka, in southern India’s state of Tamil Nadu. Gemmological research into the chemistry, properties, and characteristic inclusions of these emeralds has revealed similarities between the properties of Sankari emerald and those of emerald from several previously described locations on the island of Madagascar. This finding suggests that Sankari emeralds may have been emplaced into the ancient supercontinent of Gondwanaland before India rifted from it some 200 million years ago.

gems, gemology, phenomena, color change, usambara effect

Crystals of green chrome tourmaline from the Umba Valley (Tanzania) may show a wine-red colour when viewed in certain directions. This is neither pleochroism, nor a colour-change of alexandrite type. The change from green to red depends primarily on the path length of light through the stone and probably also on the content of Cr and V; in the samples tested the stones appear red when more than 15 mm thick. It is suggested that this new type of colour change be called the ‘Usambara effect’.

gems, history of gemology, gem trade, Persia, Central Asia, history of gem trade, Rome, India, Indian lapidary

The major routes of early maritime trade in the Red Sea and northern Indian Ocean were distinctive, characterized by the long-term movement of specific exchange commodities and their connection to particular market towns, ports, maritime conditions, tribes, and peoples. Evidence from the Periplus Maris Erythraei suggests that these trade zones were sufficiently separated by distance and resources—especially in terms of export commodities—to function as distinct but interacting exchange regions. This dual nature of separation and interactivity is reflected in the presence of well-established maritime routes along which specific trade goods circulated. Salles (1993: 506–513) describes these ancient sea routes as ‘segments’ or ‘trade units,’ whose use and control were shaped by market demands, shifts in political power, and navigational knowledge. Among these, the longest and most significant was the direct sea route from the Egyptian Red Sea coast to India.

gems, corundum, Madagascar.12

Sapphires from northern Madagascar. In the past few years, several new and important sapphire deposits have been discovered in Madagascar. Dr. Margherita Superchi, of CISGEM, Milan, Italy, described a new occurrence at Ambondromifehy, in Antsiranana Province, in the northern part of the island. The sapphires found to date were alluvial, having been weathered from basaltic rocks that were emplaced intermittently during the period from the Upper Oligocene to the Pleistocene. The sapphires are thought to be xenocryts; that is, they did not crystallize from the basaltic magma, but simply were transported by it. They are associated with zircon, spinel, pyroxene, and olivine. Dr. Superchi and her colleagues (A. Donini, D. Muzzioli, and E. Roman) obtained detailed gemological data, chemical compositions, and optical and Raman spectra for 74 crystals (the largest being 182.59 ct) and 13 cut stones. Among the more interesting discoveries were inclusions of pyrochlore, zircon, and sodic plagioclase, which, with the chemical data (e.g., high gallium contents) confirm the “basaltic” association of these sapphires (see the earlier abstract on gem corundum).

gems, corundum, Tanzania.12

East Africa continues to produce astounding gems. One example is shown in figure 17: a 2.28 ct bright slightly reddish orange natural sapphire from the Tunduru region of Tanzania, shown by Malhotra Inc., New York City. Mr. Malhotra said that he had not seen a stone of such color in his 40 years in the trade. The stone had been cut in Bangkok and may have been heat treated. Other unusual materials from Tanzania (seen at the booths of New Era Gems, Grass Valley, California) included: peridot and mint" (light green) and "honey" (brownish yellow) grossular from Mcrelani; and light-pink and light-purple to "rose pink" spinel from Pokot, near Tunduru. According to Bill Vance of New Era Gems, some blue-to-purple spinels from Tunduru look pink when viewed through the Chelsea filter, so he suspects that they contain cobalt."

corundum, Tanzania.12, gems

Tunduru-Songea gem fields in southern Tanzania.. Dr. Claudio Milisenda of the German Gemmological Association, using research done with Dr. Ulrich Henn and Dr. Hermann Bank, discussed the spectacular new gem occurrences that were discovered in late 1993 and early 1994 in the Tunduru-Songea area of extreme southern Tanzania. These alluvial deposits are located along tributaries of the Ruvuma River, which forms Tanzania’s. southern border with Mozambique. The area produces a large variety of gem materials, in particular blue and fancy-colored sapphire (including “padparadscha” and color-change stones), ruby, many colors of spinel, garnet (such as rhodolite, hessonite, and color-change), chrysoberyl (including cat’s-eye, alexandrite, and cat’s eye alexandrite), various quartz and beryl varieties, tourmaline, zircon, kyanite, scapolite, peridot, and diamond... The first gem rough appeared on the market in 1994, and included sapphire, spinel, garnet, chrysoberyl, and zircon, reportedly from an area east of Songea, where the Muhuwesi and Mtetesi rivers converge. Shortly afterwards, an even richer alluvial deposit was discovered near Tunduru, a remote area in southeast Tanzania. Because thousands of people were involved in mining and trading gemstones at the outset, it is almost impossible now to tell if some rough gems are from the Songea or the Tunduru area. With the exception of the diamondiferous Mwadui pipe within the Tanzanian craton, all of Tanzania’s known gemstone occurrences (including the Tunduru-Songea gem fields) are situated within the Proterozoic Ubendian-Usagaran System, a medium-to predominantly high-grade metamorphic unit that includes gneiss, marble, metapelite, and quartzite, which are intruded by numerous pegmatites. The Ubendian-Usagaran System forms the Tanzanian part of the Mozambique Belt. This gem-bearing complex experienced its main thermo-tectonic evolution during the Pan-African orogeny (approximately 600 million years ago), which affected the entire eastern part of the African continent as well as southern India and Sri Lanka. Dr. Milisenda also reported on the gemological characteristics of corundum, spinel, chrysoberyl, garnet, and tourmaline from the Tunduru-Songea region, which were based on the study of hundreds of carats of rough and cut stones. A visit to the localities yielded information on the geology and recovery techniques. Iron-and titanium-oxide contents of the corundum were compared with similar gem materials from Sri Lanka and India. With the exception of the occurrence of diamond and an unusual mint-green, vanadium-colored chrysoberyl, the gem gravels of the Tunduru-Songea region strongly resemble the gem concentrates of Sri Lanka, and the two areas may be genetically related. However, the large variety of gems of contrasting genetic type suggests that the gems themselves were derived from different geologic sources in both locales.

corundum, synthetic corundum.7, gems

This well-illustrated article examines (by SEM-EDX analysis) the inclusions in Russian hydrothermal ruby and sapphire manufactured by Tairus. Coatings on rough samples were found to be either boehmite or an unknown noncrystalline gel-like material. The following inclusions were observed in both rough and cut samples: solid inclusions of corroded copper (probably remnants of wire), isometric crystals and hexagonal platelets of copper, clouds and linear series of pinpoints of whitish reflective particles, tiny needles, and whitish particles (possibly alkali or calcium carbonates from the mineralizers). In pinkish red to red samples, the authors found fluid inclusion “fingerprints” or feathers, among which occur large three-phase (liquid-gas-mineral) inclusions associated with large tube-like negative crystals. The daughter minerals in the inclusions were identified (by crossed polarizers and heating/freezing [H/F] experiments) as carbonates. H/F experiments also revealed that the liquid phase is predominantly H₂O. By contrast, three-phase inclusions in natural rubies are often CO₂-rich with daughter minerals of diaspore, graphite, or mica. Of perhaps greatest interest to the practicing gemologist, the authors describe a simple gemological H/F test to distinguish between natural and synthetic hydrothermal rubies on the basis of three-phase inclusions. The copper inclusions also are indicative of synthetic origin.

gems, ancient lapidaries, alchemy, history, history of gemology

This French doctoral dissertation presents the first critical edition of the Marian bestiary embedded in the Rosarius, an anonymous medieval devotional compilation preserved in the unique manuscript Paris, Bibliothèque nationale, fonds français 12483. Mattiacci situates its fourteen surviving animal sections within a larger collection of natural descriptions, Marian allegories, miracles, pious tales and songs, which also includes a plant book and a four-stone lapidary. The introduction examines the manuscript’s provenance, damaged condition, arrangement and previous scholarship, and argues for composition between 1328 and 1337 against proposals for a later fourteenth-century date. The anonymous compiler is identified as a Dominican associated with the Soissons region. Contrary to the view that his audience consisted exclusively of nuns, Mattiacci interprets his direct addresses to both men and women as evidence for a mixed religious community. Comparative study places the work in the tradition of the Greek and Latin Physiologus and the French bestiaries, examining parallels with Pliny, Isidore of Seville, the compilation attributed to Hugh of Saint Victor, and vernacular predecessors including Richard de Fournival. Its distinctive feature is the systematic application of animal properties to the Virgin Mary rather than principally to Christ. Brief accounts of animal nature introduce substantially longer moral and devotional interpretations, sometimes interrupted by songs, a sermon or a pious tale. The edited sections concern the panther, swallow, stork, sheep, whale, caladrius, salamander, bee, swan, nightingale, dove, tortoise, camel and falcon. Their allegories celebrate Mary’s purity, humility, obedience, protective power and intercession, while supporting exhortations and criticism of contemporary conduct among clergy and laity. Of particular interest to the history of stones is the swallow’s traditional association with two precious stones, one whitish and the other reddish, said to occur within its body. A linguistic study considers phonetics, morphology, syntax, wordplay and versification, noting Picard features and irregular syllable counts. Editorial procedures include expanding abbreviations, evaluating later manuscript corrections and restoring recoverable letters lost through trimming, with interventions documented in the apparatus. Critical notes, explanatory commentary, an index of proper names, an extensive glossary and a bibliography accompany the text, making the dissertation a resource for studying medieval animal lore, Marian devotion and the transmission of vernacular religious literature.

gems, jade, jadeite, fei cui, Mesoamerica, Mexico, Guatemala, Costa Rica, Mayans, Olmecs, Aztecs, archaeology, history, archaeogemology, Pre-Columbian jade; Costa Rica; Maya; exchange; iconography, lapidary

For the back cover of the recent catalogue, Tesoros Artisticos del Museo Nacional de Antropologia, author Felipe Solis selected as an appropriately important image the well-known yet enigmatic group of stone figures standing in what is obviously a ritual situation (fig. 1).1 The group of sixteen figures and six halved celts was discovered in 1955 by Smithsonian archaeologists at the heartland Olmec site of La Venta, Tabasco, Mexico, and was dated between 750 and 650 B.C. It was designated Offering 4. The Offering (minus three figures presented to the Smithsonian) was brought to the Museo Nacional for its inauguration in 1964, and is now considered one of the most precious of its many treasures, having rarely-if ever-been allowed to leave on loan (fig. 2). This paper focuses on Offering 4 and its archaeological context as the best means for interpreting the original significance of a ubiquitous genre of Olmec portable sculpture, the Standing Figure.

gems, jade, jadeite, fei cui, Mesoamerica, Mexico, Guatemala, Costa Rica, Mayans, Olmecs, Aztecs, archaeology, history, archaeogemology, Pre-Columbian jade; Costa Rica; Maya; exchange; iconography, lapidary

The Cleveland Museum of Art houses a beautiful example of Maya handiwork in jade, referred to here as the Cleveland Plaque (fig. 1). Carved from light green mottled jade, the Cleveland Plaque measures 14.4 cm in length and 1.4 cm in maximum width and weighs 253.5 grams. The rectangular plaque has slightly rounded sides and bears an incised text that today is highlighted with an unidentified black paint. A photograph published by Kelemen (1943: vol. 2, pl. 235b) reveals that the plaque was repainted sometime before the Cleveland Museum of Art purchased it in 1950. Drilled through the centre of the plaque is a large, straight hole, about half a centimetre in diameter, which flares out into conical cavities (fig. 2). These crudely worked cavities have left the edges of the plaque very thin, and consequently they are chipped. The damage supports Kelemen’s (1943: vol. 2, p. 289) suggestion that the plaque was originally worn as a bar pectoral. Maya bar pectorals are usually flanked by other jade ornaments, which are precisely what may have chipped the thinner edges of the plaque through repeated impact. However, no holes were noted on the long, narrow edge of the plaque, so it is not clear how it was suspended from the neck. In any case, the damage provides concrete evidence that the Cleveland Plaque was used in some active fashion, probably on many occasions.