beryl, emerald, Pakistan, gems, pegmatitic emerald

Emerald is the exquisite result of the chemical substitution of a small amount of chromium (or vanadium) for aluminum in Be₃Al₂Si₆O₁₈, the mineral beryl (Deer and others, 1986). On the world gem market, if the green coloration of emerald is caused by any element other than chromium, it is not called emerald according to standards adopted by the London Chamber of Commerce and Industry’s Precious Stone Trade Section (Farm, 1975). The coexistence in nature of chromium and beryllium is unusual and thus emerald is one of the rarest and most precious gemstones. The general incompatibility of beryllium and chromium is the result of their different geochemical behavior as clearly demonstrated in the compilation of chemical data for igneous rocks by Wedepohl (1978). Beryl, the most common beryllium mineral, forms during late-stage (pneumatolytic and hydrothermal) igneous activity. Because Be²⁺ has a small ionic radius (approximately 0.3 Å; Shannon and Prewitt, 1969), it is excluded from the crystal structure of most minerals. In addition, because of the small average continental crustal abundance of beryllium (less than 5 ppm; Wedepohl, 1978), beryllium is not concentrated enough to form beryl until late stages of igneous activity, i.e., during the formation of pegmatites or hydrothermal deposits. In contrast, chromium, also a trace constituent in the Earth’s crust (averaging approximately 50 ppm; Wedepohl, 1978), precipitates early during igneous fractionation in the mineral chromite, FeCr₂O₄, or it substitutes for aluminum, iron, magnesium, or titanium in early igneous phases, such as pyroxene, amphibole, spinel, or garnet. Thus, the greatest abundance of chromium is found in ultramafic and mafic rocks. So even though chromium, which has an ionic radius of 0.62 Å (Cr³⁺; Shannon and Prewitt, 1969), will readily substitute for aluminum, which has an ionic radius of 0.54 Å (Al³⁺; Shannon and Prewitt, 1969), in the beryl crystal structure, chromium is not expected in the late-stage liquid or vapor from which beryl may be formed. Special circumstances are necessary to bring chromium and beryllium together; as a result, emerald is extremely rare and is found only where geologic processes have been favorable for its formation. One of the places on the Earth where the geologic environment is appropriate for emerald occurrence is the area of northern Pakistan and Afghanistan. In this region, oceanic and island arc rocks that are rich in chromium are juxtaposed against felsic, beryllium-bearing continental rocks of the Indian plate. Within this geologic setting, emeralds are found in two very different geologic environments. In the economically most important deposits, emeralds formed from hydrothermal fluids that penetrated along shear zones into talc-carbonate schists within mélange zones. In the other setting, the emeralds are in pegmatites or quartz-ankerite veins which intruded schist, gneiss, and amphibolite. In both cases, the beryl apparently precipitated from a late-stage beryllium-carrying hydrothermal or pneumatolytic fluid which had scavenged chromium from the host rock.

gems, beryl, emerald, Pakistan, Gujar Killi, Swat, Mingora

Over the last decade, Pakistan has developed into an important source for many gem materials. A number of localities have been identified for emeralds in particular. This article reports on the emerald deposits in the valley of Gujar Killi, located in the Northwest Frontier Province. The occurrence, mining, and gemological properties are described. Reserves appear to be good, and increased mining activity suggests strong production for the near future.

gems, beryl, emerald, Colombia, gold, shipwrecks, Florida Keys

During the 1970s and 1980s, treasure hunters discovered the centuries-old re-mains of the sunken Spanish galleons Nuestra Senora de Atocha and Santa Mar-garita. Not only did they find massive amounts of silver and gold in coins, bars, and chains, but they also uncovered a number of rough emeralds and several pieces of emerald-set jewelry. Recently, some of the treasures recovered from the Atocha were examined at the Santa Monica office of the GIA Gem Trade Lab-oratory. Gemological testing of the emer-alds revealed inclusions typical of stones mined in Colombia as well as possible ev-idence of extended submersion in s e w -ter. Study of the jewelry revealed a high-karat gold content and fine workmanship that represented methods typical of the era.

gems, jade, ruby, sapphire, spinel, beryl, emerald

A sumptuous catalog that accompanied shows in New York, Los Angeles and Toledo. Many aspects of the artistry and architectural skills that went into the creation of the world's most famous mausoleum are revealed. The buildings' depiction in artists' imaginations is also covered from many perspectives through the ages, by admirers from every culture. This article from the book focusses on Mughal jades.

corundum, History.1, gems, Indian lapidary

The fourth chapter of the Rasa Ratna Samuccaya, presented in Sanskrit with English translation and extensive explanatory notes by Damodar Joshi, is devoted principally to ratnas (gems) and is particularly important for the history of Indian gemology. Nine principal gems are associated with the nine planets: ruby, pearl, coral, emerald, topaz, diamond, sapphire, hessonite and cat’s-eye. The text describes desirable and defective qualities of gems and gives procedures for their śodhana (purification) and māraṇa (incineration) for medicinal use. Individual sections discuss ruby, sapphire, diamond, pearl and other gem materials, including their traditional physical characteristics, varieties, supposed planetary relationships, therapeutic properties and methods of processing. Additional materials treated include sunstone, moonstone, lapis lazuli and quartz (sphaṭika). Joshi’s notes compare the traditional descriptions with modern mineralogical identifications and chemical compositions. The chapter provides unusually detailed evidence for the intersection of gemology, medicine, astrology and alchemy in the Indian rasaśāstra tradition.

gems, ancient gemology, ancient jewelry, Egypt, Egyptian jewelry, beryl, emerald, turquoise, malachite, Islamic jewelry, Arabic mineralogy, rings, glyptic, engraved gems, gold

Hasson’s two-volume catalogue presents the Islamic jewellery collection of the L.A. Mayer Memorial Institute for Islamic Art, tracing the development of personal ornaments across the Islamic world from the early Islamic period into later centuries. The objects include rings, earrings, bracelets, necklaces, pendants, beads, amulets, belt and costume fittings, and related ornaments fashioned in gold, silver, and other materials and frequently set or decorated with gemstones, glass, and enamel. Individual entries describe materials, techniques, dimensions, decoration, inscriptions, provenance, dating, and comparable pieces, placing the jewellery within its archaeological and art-historical context. Particular attention is given to manufacturing and decorative techniques such as casting, repoussé, filigree, granulation, engraving, niello, openwork, and stone setting, as well as to recurring geometric, vegetal, figural, and epigraphic motifs. The catalogue illustrates both the continuity of jewellery forms across the Islamic world and regional differences resulting from interactions with Byzantine, Sasanian, Central Asian, Mediterranean, and other traditions. Together the volumes provide an important reference for the identification, dating, manufacture, and stylistic development of Islamic jewellery and for the study of gemstones and precious materials in Islamic decorative arts.

gems, beryl, emerald, inclusions, Brazil, Colombia, etc.

A comprehensive study of inclusions in emerald, with particular emphasis on their use in gemological identification and determination of geographic origin. Schwarz examines solid mineral inclusions, fluid inclusions, growth features and other internal characteristics of emeralds from the principal producing localities, comparing their characteristic inclusion assemblages. Brazilian occurrences receive extensive treatment, including Carnaíba and Socotó in Bahia, Santa Terezinha in Goiás, and deposits in Minas Gerais, alongside material from Colombia and other world sources. The work illustrates how combinations of mineral inclusions, fluid inclusions and growth structures can distinguish emeralds from different geological environments and can assist in separating natural from synthetic material. It became an important reference for subsequent studies of emerald inclusions and geographic origin. Sadly this softcover book was poorly printed on low quality paper.

precious stones, gems, jewelry

A lavishly illustrated survey of gemstones and precious objects, tracing their significance from prehistory and traditional societies through the great jeweled treasures of Europe, Asia and pre-Columbian Mexico. Separate sections examine glyptics, jade, and the authentication of engraved and historically important gems. The geographical portion surveys the principal world sources of diamond, ruby, sapphire, emerald and other gem and ornamental materials, while the final section considers the changing value of gemstones through history, the contemporary gem trade and international markets. Appendices provide a systematic classification of minerals and varieties used as gems. The emphasis throughout is on the relationship between gemstones and human culture—history, craftsmanship, symbolism, collecting and commerce—supported by extensive, largely color photography. A contemporary Journal of Gemmology review particularly praised the production and the many photographs that were new to publication.

beryl, emerald, Colombia, Muzo, Coscuez, gems

The Muzo emerald district, in Boyacá, Colombia, contains several mines. Although the Muzo mine is undoubtedly the best known, the Coscuez mine is rapidly gaining significance as a major source of fine emeralds. Yet few in the trade outside of Colombia are aware of the importance of Coscuez or know about the emeralds mined there. The Coscuez mine is literally hundreds of years old, and its history is closely tied to that of Muzo. Located only about 10km apart,the two areas also share many geologic features and both are currently exploited using open-cut mining methods. The Cosccuez emeralds are similar to Muzo stones in their physical properties, but they occurin a somewhat broader range of hue and saturation. Prospects for even greater production at Coscuez in the future are good.

corundum, USSR.12, Tajikistan.12, Russia.12, gems, jade, nephrite, diamond, beryl, emerald, tourmaliine, aquamarinte, diopside, charoite, fei cui, jadeite

Sinkankas: The most comprehensive and authoritative treatise in modern times of the gemstones of the USSR, with good color photographs of cut & rough gemstones, countryside views, mining activities, etc., and all attractively designed and on good quality paper. Unfortunately, only the illustration captions are in English. p. 4: ‘This book includes detailed characteristics of the main species of gems and semiprecious stones in the USSR. Descriptions of geological, structural, genetic and other factors of the origin and distribution of gemstone formations are given. The territory of the country is divided into ore regions of gemstone raw materials with regard for main geological and structural and economic regions. Complex and monomineral provinces of gemstone raw material are marked out. The distinction and cutting of natural gemstones and their imitations are examined.’ In addition to the expected geological/mineralogical treatment as indicated in the foregoing resume, it should be noted that Part 6, on the history of the development of the manufacture of many types of articles from gemstones and stone, is especially rich in illustrations of all manner of articles from massive stone monuments, urns, etc., to articles of personal adornment, crown jewels of Tsarist days, peasant jewelry, small animal carvings, and many more. As noted by M. J. O’Donoghue in his review, J Gemm, 20, 4, 1986, 254–5, ‘there are many quality colour pictures and even for those with no Russian these make the book well worth getting.’ I have seen another issue of the present work, dated 1985, same price, bound in plain, olive-green cloth-type paper over boards.