beryl, emerald, Pakistan, gems, pegmatitic emerald, emerald geology

Emerald, formed by the substitution of a small amount of chromium for aluminum in the beryl crystal structure (Deer et al., 1986), results from rare geological conditions. While beryl—the most common beryllium-bearing mineral—is itself uncommon and primarily found in late-stage igneous rocks like pegmatites, emerald is even rarer due to the geochemical incompatibility between its two essential components: chromium and beryllium. Beryllium, with a small ionic radius (0.3 Å; Shannon and Prewitt, 1969) and a low crustal abundance (less than 5 ppm per Wedepohl, 1978; or less than 3.5 ppm according to Beus, 1965), is generally absent from the chromium-rich, ultramafic rocks where chromium resides in significant concentrations. Thus, emerald formation requires exceptional conditions that bring these two incompatible elements together, making emerald one of the rarest and most valuable gemstones. In Pakistan, a unique sequence of geological events created such conditions. The first three chapters of this book summarize these large-scale events, while chapters four through seven examine clues about emerald formation revealed through the physical and chemical characteristics of the crystals and the morphology and physicochemical formation conditions of their inclusions. Chapter 8 reviews the geology of other global emerald deposits. This cumulative analysis reveals a broader understanding of both Pakistani and global emerald genesis. The concluding chapter summarizes the characteristics of Pakistani emeralds and uses this data to formulate a theory of their origin, then proposes a classification scheme based on the geologic setting of global emerald deposits, developing it into a hypothesis for the genesis of all emeralds. Finally, suggestions for future research are offered to further elucidate emerald formation processes.

gems, inclusions, beryl, emerald, Brazil

beryl, emerald, Pakistan, gems

This is a comprehensive study of emeralds and emerald deposits in Pakistan. Nine chapters include: a review of geology and metallogenic provinces of Pakistan; geological setting of Pakistani emerald deposits; detailed description of each of the Pakistani emerald deposits known before 1989; gemological characteristics of Pakistani emeralds; regional chemical differences among emeralds and host rocks of Pakistan and Afghanistan; mineral chemistry of emeralds and associated minerals; a fluid inclusion study; geology of world emerald deposits; and origin and classification of Pakistani and world emerald deposits. The book also includes a comprehensive bibliography of the emerald deposit literature up to 1989. With color photos by E.J. Gübelin

corundum, sapphire, geology.11, East Africa.12, Kenya.12, gems

A new sapphire deposit has been discovered in Kenya's Turkana Province. Transparent dark blue and greenish blue sapphires, as well as star sapphires are now available in the gem market. Heat-treatment experiments have produced fine medium-blue sapphires, reminiscent of their Thai and Kampuchean counterparts. This article resulted from the author's experiments, his detailed examination of the material and a personal visit to the area in November, 1988. An appendix discusses the typcal inclusions of this material.

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

In 1990 the scholarly world commemorated the 400th anniversary of the death of Bernardino de Sahagún, widely regarded as the most systematic and innovative early ethnographer of the cultures of the Americas and among the first investigators to experiment with methods resembling modern anthropology. It was therefore fitting that the Institute for Mesoamerican Studies publish a volume devoted to the results of his nearly sixty years of “field work” among the Nahuatl-speaking peoples of Mexico. The institute took particular pride in issuing the book in time to encourage reflection during the years in which the name of this celebrated Franciscan would be frequently invoked by Mesoamericanists around the world. Special thanks were extended to H. B. Nicholson and Eloise Quiñones Keber, coeditors of the volume, for their timely and thoughtful assistance throughout the preparation of the manuscript. The author also gratefully acknowledged support from the John Simon Guggenheim Memorial Foundation, whose fellowship made it possible to complete the volume on schedule by relieving many competing obligations.

gems, emerald, oiling, treatments, enhancements, fillers

This paper does not wish to deal with the luck of a Texan property owner, but rather to share my experience in the gemmological laboratory. The article could just as well be titled: What many people do not yet know about oiling emeralds, and others at times tend to forget. ”Cemmosophic” literature likes to use the French term jardin” (Engl.: garden) for typical, vei|—like inclusions visible to the naked eye. These internal structures, resembling leaves and tendrils, are commonly classified as healed fissures, but often also as open cracks. The latter are usually considered to be negative properties."

corundum, inclusions.5, treatments.6, chemistry.2, color.4, gems

gems, quartz, synthetic quartz, synthetic amethyst, Japan, hydrothermal, polysynthetic twinning

Synthetic amethysts of Japanese production, which are now available in the gem trade, are characterized with respect to their diagnostic properties such as inclusions, growth structures, twinning, and infrared spectra. The gemstones frequently have feathers consisting of liquid-filled and two-phase inclusions, sharp growth zoning parallel to one rhombohedral face, as well as twin structures. This twinning, however, can be distinguished from polysynthetic lamellar twinning in natural amethysts.

corundum, synthetic corundum.7, Lechleitner, flux, gems

Describes Lechleitner rubies consisting of natural pale ruby or colourless corundum cores from Sri Lanka covered by a thin, flux-grown synthetic ruby layer. The cores include rough, bruted and faceted material and retain natural mineral and fluid inclusions, while the synthetic overgrowth contains flux residues. Six faceted specimens show violet-tinged colours resembling Sri Lankan rubies and pink sapphires. Identification requires careful microscopic examination, particularly of the boundary between core and overgrowth, which can resemble early Knischka synthetic rubies. Trace-element analysis, including examination of flux residues, together with X-ray fluorescence, electron microprobe analysis and spectroscopy, can assist identification.

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.