corundum, ruby, sapphire, Vietnam.12, inclusions.5, geology.11, gems

Northern Vietnam began producing significant quantities of rubies and fancy sapphires in the late 1980s. Since then, mining has evolved at the two major producing areas: Luc Yen and Quy Chau. Heavy machinery is now used in both of these remote areas, but small-scale manual mining is ongoing. Efforts continue to establish organized cutting and distribution centers.

corundum, inclusions.5, Montana.12, USA.12, gems

This article offers a brief description of the history and geology of the Yogo sapphire deposit the largest producer of gem sapphires in the Western Hemisphere. Until recently, the mine was largely inactive, and the factors leading to this period of low production and the associated economics of the deposit are discussed. Recent discoveries at the deposit and the development of a new mine in a sapphire rich zone mean that Yogo sapphires may become more well known than in the past. The gemology of this relatively inclusion-free and typically untreated gemstone is also discussed. Photographs of some of the inclusions that do exist are presented.

corundum, sapphire, Nigeria.12, inclusions.5, geology.11, gems

corundum, ruby, sapphire, Malawi.12, inclusions.5, gems

corundum, ruby, sapphire, synthetic corundum.7, treatments.6, properties.3, color.4, inclusions.5, gems

Anderson’s Gem Testing is one of the most important gemology books of the 20th century. Revised many times as gemology changed, after his death, Alan Jobbins continued the tradition. Not surprisingly, this is the best of the editions, and should be on the shelf of every gemologist. In 2013, Anderson was named in the French Association of Gemmology’s 50 most influential gemmologists of all time.

India.12, Kashmir.12, inclusions.5, gems

This investigation was undertaken to contribute to the knowledge of sapphire from Kashmir, and over 50 cut stones were studied. Comparison of the observed inclusions with those described in other publications, identified in part using the scanning electron microscope SEM/EDS, confirmed the results of earlier findings (tourmaline, pargasite and zircon inclusions). In addition, some internal characteristics are newly described: plagioclase, uraninite, allanite and rutile (P) occurring in various forms, healed fissures and zoned growth. Spectral properties are presented. The significance of origin reports is discussed.

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.