gems, beryl, emerald, Colombia, Chivor, Muzo

Las primeras esmeraldas colombianas fueron descubiertas, el año de 1514, en Santa Marta, Costa Norte, por el Capitán General Pedro Arias de Ávila. Durante la conquista se requisaron muchas a los indios y también se recogieron en placeres, lo que ponía en evidencia la riqueza de este país. En 1535, el naturalista Gonzalo Fernández de Oviedo (1478-1557) nos señala en la Historia Natural y General de Indias (1535) que desde Tierra Firme 'se han llevado muchas (esmeraldas) en cantidad de diversas estimaciones, é precio', oferta tal que llevó a la caída de precios en Europa.

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

A Roman gold signet-ring (Pl. XXb) was discovered in 1974 in a garden at Brackley, Northamptonshire, and was later submitted by the finder for examination at the Buckinghamshire County Museum, Aylesbury. The find-spot, located in Watery Lane, lies just north of a building that has yielded pot-sherds, tile, brick, slate, tesserae, and flint—suggesting a possible villa, though Roman activity appears widespread in the area, indicating the building may have been part of a larger settlement. The ring is made of high-purity ancient gold and features a hoop with a rounded section that expands from 3 mm at its narrowest point to 6.5 mm at the bezel; its external width is 18 mm (internal width 12 mm) and its height, including the stone, is 16 mm (internal height 11 mm). Set into the bezel is a green translucent stone with dark inclusions, initially believed to be a chrome-rich chalcedony (plasma), as is common in Britain, but identified through X-ray fluorescence analysis by the British Museum Research Laboratory as an emerald. Known in antiquity as smaragdus, emeralds were highly prized though rarely engraved due to their hardness—making this the first known emerald intaglio from Roman Britain. The gem, which has a convex profile and measures 8 mm by 5 mm, is engraved with the image of the corn-goddess Ceres (Greek, Demeter), sometimes conflated with the Roman Fides Publica on coins. She is depicted standing frontally, dressed in a belted chiton, holding two heads of corn in her left hand and a dish of fruit in her right—an image that would appear in reverse in impression (Pl. XXc).

gems, chrysoberyl, alexandrite, beryl, emerald, phenakite, Galicia, Franqueira, Spain

jade, jadeite, fei cui, Burma, gems

Jadeite may be white, pink, lilac, brown, red, orange, blue, black or many shades of green, and contains different trace elements as colouring agents. Of these trace elements, iron shows the highest concentration and its oxidation states of ferrous or ferric iron produce different colours. In white jadeite nearly all iron is present as ferric (trivalent) iron, while in black jadeite half is ferrous (divalent) and half ferric. In the leaf green jadeites the Fe2+ /Fe3+ ratio ranges from 0.1 to 0.2. The finest green Burmese jadeite, whose colour is caused by up to 0.3 per cent chromium, has been called Imperial jade' or 'emerald jade'. Contents of iron (up to 0.6% Fe) and nickel (0.04% Ni) can modify the rich chromium green of the jadeite. Lilac, mauve or lavender jade may contain manganese (up to 0.01% Mn), cobalt (up to 0.001% Co), chromium (up to 0.001% Cr) and iron (from 0.006 to 0.3% Fe).

corundum, Australia.12, Queensland, Anakie, gems

gems, jade, jadeite, fei cui jade, synthetic jadeite, fei cui

Jadeite was synthesized from its glass of stoichiometric composition NaAlSi₂O₆, and a colouring agent Cr₂O₃ (0.3–0.6 wt%) was added to achieve the emerald colour. The conditions employed were a pressure range of 3.0–5.0 GPa and a temperature range of 1150–1750°C, for periods of 1–480 min. The physical and chemical properties of synthetic jadeite, such as microstructure, unit cell parameters, melting point, thermal stability, hardness, density and refractive index, etc., were compared with those of natural jadeite. The optimum crystallizing conditions for the synthesis of jadeite for jewellery were above 4.5 GPa, 1450°C and 60 min. The synthetic jadeite was emerald in colour, translucent, 12 mm in diameter and 6 mm thick.

corundum, history.1, quality.10, India.12, Tajikistan.12, spinel, beryl, emerald, ruby, diamond, gems, Indian lapidary

gems, beryl, emerald, Egypt

Grundmann and Moretani provide a historical, mineralogical, and geological study of Egypt’s ancient emerald-mining district, concentrating on Zabara, Sikait, and Umm Kabo in the Eastern Desert. They review ancient references to Egyptian emeralds and the history of exploration and rediscovery of the workings, while noting the confusing nomenclature applied to the individual mining localities. The authors describe extensive ancient excavations and settlement remains and discuss evidence for mining over a long period, including Pharaonic, Ptolemaic, Roman, and later activity. Detailed geological sections examine the emerald occurrences within the Precambrian metamorphic complex, particularly their association with mica and biotite schists, serpentinites, talc-carbonate rocks, granitic and pegmatitic bodies, and structurally controlled zones of deformation and fluid activity. The three principal localities are treated separately, with descriptions of their mineral assemblages, host rocks, emerald-bearing zones, and proposed processes of emerald formation. The authors emphasize the importance of tectonic structures and hydrothermal or metasomatic processes, with beryllium-bearing fluids interacting with chromium-bearing rocks to produce emerald. Numerous maps, geological diagrams, photographs of the mines and workings, and photographs of emerald specimens illustrate both the archaeological and mineralogical aspects of the deposits.

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

We know that in the most advanced civilizations jade was used for ceremonial and ornamental objects; the characteristic most admired was its hardness, which best served artistic expression, together with its ability to receive and retain a lustrous polish (Foshag 1954:3). Jade was a stone of particular significance to the people of pre-Columbian Mesoamerica, for whom it was “the precious stone of grace, the first infinite grace, its green colour forming an allegorical metaphor for young maize, flowing water, and life itself” (Thompson 1950). In Group A-IV-1 at Kaminaljuyú, during excavations carried out in 1990 and 1991, a small but important assemblage of greenstone artefacts was recovered (Figure 1). Apparently, the first European contact with the material occurred in the sixteenth century through specimens brought back by the Spanish, rather than, as might be assumed, through contact with China (Foshag 1957:2). The word jade was coined in France as a derivation of the term piedra de ijada (“stone of the flank”), used by Spanish chroniclers to refer to this green stone arriving from the Americas, to which medicinal properties against kidney ailments were attributed (Hammond et al. 1977:38). By the time of the Conquest (Foshag 1954), several types of jade were distinguished among the Aztecs: chalchihuitl, which could be translated as “green-grass jewel stone,” referring to ordinary jade; quetzalitli, named after the iridescent green tail feathers of the quetzal, probably denoting the finest translucent emerald-green jade; tlilayutic, which may refer to dark chloromelanite; and white chalchihuitl, which appears to have been albite-jadeite. In addition to the identification of different qualities of the mineral, there is evidence of a preference among the elite for the finest-quality jades, a pattern that can also be traced back to Preclassic groups. With the Spanish conquest and the replacement of indigenous cultures, the use and knowledge of jade disappeared; along with it, the associated folklore was also lost.

gems, garnet, grossular, hessonite, India, Orissa, tourmaline, sillimanite

The state of Orissa in eastern India has emerged as an increasingly important source of gemstones. Since 1989, rising quantities of rhodolite garnets from the region have been seen, followed by notable finds of aquamarine and ruby. At the 1993 Tucson Show, Amar J. Jain presented a 2.99 ct faceted alexandrite and dark grayish blue tourmalines from Orissa, one of which—a 1.74 ct emerald-cut specimen—showed gemological properties consistent with tourmaline from other locations, including refractive indices of 1.620 and 1.640, birefringence of 0.020, and specific gravity of 3.11. Hessonite (grossular) garnet is also being mined near Kanta Bhaji in the Kalahandi area, with faceted stones ranging from reddish orange to orangish brown; many exhibit a pronounced “roiled” appearance typical of Sri Lankan hessonites, sometimes resembling translucent sard. A 2.19 ct orange stone tested with an R.I. of 1.748 and S.G. of 3.65, confirming it as hessonite. Following the show, the editors received a report from Shyamala Fernandes of the Gem Testing Laboratory in Jaipur describing a December 1992 find of chatoyant sillimanite, initially misidentified and marketed as “moonstone cat’s-eye.” Identified as sillimanite, the material exhibited an R.I. of 1.659–1.678 (1.66 spot), S.G. of 3.25, biaxial optic character, and Mohs hardness of 7–8. Microscopy revealed parallel acicular inclusions responsible for the chatoyancy, along with “fingerprint” two- and three-phase inclusions and black platelets. The sillimanite occurs in colors ranging from colorless to gray, pinkish brown, yellow, green, and blue-green, typically in lighter tones, and most cabochons—some up to 20 ct—display sharp cat’s-eyes and a vitreous luster. Though precise production data is lacking, the material has been readily available in Indian markets since its discovery.