gems, inclusions, beryl, emerald, Madagascar

Inclusions in emeralds from the Mananjary region in the eastern part of the island nation of Madagascar are reported and compared with inclusions in emeraldsf rom other, especially African, localities. Although most of these internal features are similar to those found in emeralds from other schist-type deposits, Mananjary emeralds usually can be separated from emeralds from other localities by means of associations of certain mineral inclusions (especially talc, carbonates, amphiboles, and quartz) with specific types of fluid inclusions.

gems, beryl, emerald, Egypt, inclusions

Egypt is the most ancient of sources for emerald. More than 2,000 years ago, emerald deposits in upper Egypt were supplying gems throughout the Graeco-Roman Empire. A recent visit to this emerald province revealed that the emeralds occur within a northwest-southeast trending belt of schistose rocks in the Red Sea Hills, near the port town of Marso Alam. At the time of the visit, there was no official commercial mining of emerald in the region, although there was evidence of sporadic activity by Bedouin tribespeople. Gemological examination of 14 cut emeralds and green beryls revealed properties consistent with those of material from similar geologic environments.

corundum, Burma.12, Montana.12, USA.12, gems, pearls, diamond

Edwin Streeter was a leading Victorian jeweller of his day who, rising from humble beginnings, masterminded the exploitation of the Burma Ruby Mines and opened up the Pearl Fisheries of Western Australia. Other expeditions, seeking Diamonds in South Africa, Sapphires in Montana and Emeralds in Egypt, were disastrous. After a long, controversial and colourful career, he was to die in genteel poverty in Hampstead in 1923.

gems, beryl, emerald, Colombia

A condensed historical and mining survey is followed by a compilation of the most notable crystals of Colombian emeralds ever found and of the details of their chemical composition. A summary of the elemental substitutions and their effects on the outlined range of gemmological data is given. Special emphasis is placed on the cause of the famous, vividly green coloration, i.e. on the selective absorption of orange-red and violet light, dictated by minor contents of the chromophoric elements Cr and V substituting for Al³⁺ in octahedrally coordinated sites of the beryl lattice (Cr ≈ V, with the Cr/V ratio found to be ranging from 4.5 to 0.5, in extreme cases from about 10 to 0.1). Iron, however, has barely been detected in the UV/VIS absorption spectra of Colombian emeralds. Though generally present in slightly larger amounts than Cr³⁺, iron does not recognizably influence the colour (little Fe²⁺ and possibly some Fe³⁺ positioned in the axial channels of the ring-silicate structure). A detailed presentation of the currently known internal characteristics (inclusions and growth structures) is supplemented by a discussion of identification problems with treated emeralds and the disclosure of the treatment during transactions in the wholesale and retail trade. Allocation of the emeralds to individual Colombian mines on the basis of inclusion patterns does not appear possible in most instances. However, the differentiation of Colombian emeralds from other natural emeralds (such as those from the Panjsher Valley exhibiting very similar (s,l,g) three-phase inclusions) or from difficult, modern hydrothermal and flux synthetics is shown to be feasible by a combination of microscopy, refractometry, and absorption spectrometry (UV/VIS and NIR/MIR), assisted by chemical analysis only in the most difficult cases. Safe identification of authenticity, treatment, and origin of emeralds, however, is increasingly becoming the task of the experts in the specialized laboratory. The mineralogical definition of emerald as a yellowish to bluish-green variety of natural beryl is shown to be valid for any Cr and V-containing variety except possibly the rare, absolutely chromium-free (V,Fe)-beryls (modification of the former definition of type II emerald): in many of the preferred Colombian emeralds, chromium is clearly dominated by vanadium (Cr/V ratio < 1). However, chromium has a higher efficiency of coloration than vanadium and a much higher one than iron ions in the various substitutional and interstitial lattice sites of beryl. Cr influences colour even at very low trace levels. An extensive and up-dated selection of literature, covering all aspects cited, completes the synopsis.

gems, beryl, emerald, Colombia

A condensed historical and mining survey is followed by a compilation of the most notable crystals of Colombian emeralds ever found and of the details of their chemical composition. A summary of the elemental substitutions and their effects on the outlined range of gemmological data is given. Special emphasis is placed on the cause of the famous, vividly green coloration, i.e. on the selective absorption of orange-red and violet light, dictated by minor contents of the chromophoric elements Cr and V substituting for Al³⁺ in octahedrally coordinated sites of the beryl lattice (Cr ≈ V, with the Cr/V ratio found to be ranging from 4.5 to 0.5, in extreme cases from about 10 to 0.1). Iron, however, has barely been detected in the UV/VIS absorption spectra of Colombian emeralds. Though generally present in slightly larger amounts than Cr³⁺, iron does not recognizably influence the colour (little Fe²⁺ and possibly some Fe³⁺ positioned in the axial channels of the ring-silicate structure). A detailed presentation of the currently known internal characteristics (inclusions and growth structures) is supplemented by a discussion of identification problems with treated emeralds and the disclosure of the treatment during transactions in the wholesale and retail trade. Allocation of the emeralds to individual Colombian mines on the basis of inclusion patterns does not appear possible in most instances. However, the differentiation of Colombian emeralds from other natural emeralds (such as those from the Panjsher Valley exhibiting very similar (s,l,g) three-phase inclusions) or from difficult, modern hydrothermal and flux synthetics is shown to be feasible by a combination of microscopy, refractometry, and absorption spectrometry (UV/VIS and NIR/MIR), assisted by chemical analysis only in the most difficult cases. Safe identification of authenticity, treatment, and origin of emeralds, however, is increasingly becoming the task of the experts in the specialized laboratory. The mineralogical definition of emerald as a yellowish to bluish-green variety of natural beryl is shown to be valid for any Cr and V-containing variety except possibly the rare, absolutely chromium-free (V,Fe)-beryls (modification of the former definition of type II emerald): in many of the preferred Colombian emeralds, chromium is clearly dominated by vanadium (Cr/V ratio < 1). However, chromium has a higher efficiency of coloration than vanadium and a much higher one than iron ions in the various substitutional and interstitial lattice sites of beryl. Cr influences colour even at very low trace levels. An extensive and up-dated selection of literature, covering all aspects cited, completes the synopsis.

beryl, chrysoberyl, beryl, emerald, alexandrite, Russia, Urals, Malysheva, gems

Emeralds are again being mined in the historic district of the Ural Mountains. Physical, chemical, spectroscopic, and ini-croscopic characteristics of stones from the recent production are presented and com-pared with data on older samples as well as those reported in the literature. Chemi-cal analysis and visible and infrared spec-troscopy provide information on crystal chemistry and color-causing trace ele-ments that is useful both to characterize these stones and to separate them from their synthetic counterparts. A variety of mineral inclusions as well as liquid, two-phase, and three-phase inclusions were seen with magnification. All of the data are critically evaluated with respect to the confirmation of unknown samples as Uralian.

corundum, synthetic corundum.7, gems

gems, history of gemology, beryl, emerald, emerald lore, gem lore

This study, centered on a particular medium, is drawn from a broader investigation encompassing all types of support related to Le Griffon, from archaism to the imperial era (Étude iconographique et essai d’interprétation symbolique, Bruxelles-Rome, 1980). Since then, other documents—particularly from Picardy, in Amiens and Soissons—have been discovered, enabling us to resume and extend this line of research. The iconographic motif of the griffon—a hybrid creature combining the body of a lion with the foreparts of a winged bird of prey—is very ancient: it originated in Egypt and Elam around 3000 BCE and enjoyed significant popularity until about 1200 BCE, spreading into other cultural spheres surrounding the Mediterranean. After a period of decline, it reappeared in the Greek world in the last quarter of the 8th century BCE. During this archaic period (from the 8th to the 6th–5th century), the dominant type was the griffon with a winged lion’s body and the head of a raptor, closely related to griffon protomes, though with some variation in detail. It is also during this time that we find the bird-bodied griffon, characteristic of Protocorinthian and Corinthian pottery.

beryl, emerald, Colombia, Chivor, Muzo, gemology of emeral, gems

A large-format, extensively illustrated monograph devoted to the emerald, with particular emphasis on Colombian emeralds. Written by a number of specialists from Europe and the Americas, it surveys the emerald through history; its mineralogy, geology and formation; the principal Colombian deposits and mining regions; mining and production; gemological properties; color, crystal morphology and cutting; and the place of emeralds in jewelry and the decorative arts. Historical sections trace the use and appreciation of emeralds from antiquity through the Spanish encounter with Colombia and into the modern trade. Numerous color photographs reproduce important emerald crystals, cut stones, jewels and works of goldsmithing from museums and private collections. The volume combines gemological and geological information with the cultural and historical importance of emerald and is particularly valuable as a substantial Spanish-language reference on the Colombian emerald industry. Contemporary descriptions confirm that the text was contributed by multiple specialists rather than being solely authored by Martín de Retana.

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.