The study of solid inclusions (Figure 1) remains one of the most relevant sources of information for determining the geographic origin of gemstones. The minerals trapped or absent as inclusions within emerald crystals directly reflect the local geology and host rock characteristics of the specific deposits where they formed, varying distinctly from one location to another.
Through micro-Raman analysis of a large reference collection of emeralds, combined with an exhaustive review of the scientific literature on mineral inclusions in this gemstone, we were able to identify significant markers that support the reliable attribution of geographic origin.

Materials and Methods

All photomicrographs were acquired using a VHX 7000 digital microscope at the Bellerophon Gemlab laboratory in Bangkok, with magnifications ranging from ×30 to ×2500.
The 1628 samples were acquired either directly at the mine, or from the miner close to the mines, or in the market from trusted contacts (Table 1). Weighing between 0.17 and 43.61 carats, they included polished wafers (with two windows), rough stones, and faceted gems. UV-Vis-NIR spectra were also collected at Bellerophon Gemlab using an Ocean Insight SR-4XR250-50 spectrometer with 500 lines blazed at 250 nm, a 50 μm slit, and coupled with a 10-watt halogen and 1.2-watt xenon light source.
Raman spectra were obtained at Bellerophon Gemlab using a BWT-8400000340 i-Raman Plus 532S. For internal inclusion analysis, the system was operated in confocal mode with 20X and 50X objectives using 532-nm highly coherent lasers.

Low Iron Type and High Iron Type

Emeralds can be classified into two distinct groups: low iron type and high iron type, based on the relative presence of the Fe²⁺ absorption band at 825 nm observed in their respective UV-Vis-NIR spectra (Figure 2).
This spectral distinction, combined with the presence of specific solid inclusions, makes it possible to highlight certain geographic origins. Indeed, some inclusions are found in only one low iron deposit but may also occur in one or more high iron deposits.
Low iron deposits notably include Colombia (Muzo and Chivor), Zambia (Musakashi), and Afghanistan (Panjshir). In contrast, high iron deposits comprise a broader range of sources, including Australia (Torrington, Emmaville/Torrington, Poona), India (Jharkhand, Rajasthan), Brazil (Minas Gerais, Bahia, Goias), China (Davdar, Malipo), Ethiopia (Shakiso), Madagascar (Mananjary, Ianapera), Nigeria (Jos Plateau), Norway, Pakistan (Chitral and Swat), Russia (Malysheva), South Africa, Tanzania (Lake Manyara), Zambia (Kafubu), and Zimbabwe (Sandawana).

Classification and Distribution by Strunz Class

A total of 114 different inclusions were analyzed in emeralds from a wide range of geographic sources worldwide. An initial classification of these minerals was carried out according to the Strunz system (Table 2), which groups mineral species into ten major categories based on their chemical composition and the nature of their anionic groups.
Among the inclusions identified, silicates represent the most diverse class, with 51 different mineral species observed in emeralds, followed by oxides, sulfides, and carbonates.
In contrast, halides, borates, and native elements are the least represented classes, with only 3 and 2 minerals recorded in each of these categories.

Mineral Inclusions with Low or High Indicative Value for Geographic Origin

The most frequently observed solid inclusions in emeralds are quartz, followed by calcite and apatite. Table 3 presents the ten most common inclusions found in the samples analyzed.
Although their presence is not relevant for determining geographic origin, these inclusions have, to date, never been identified in synthetic emeralds, making them useful indicators for distinguishing natural from synthetic gems.
Conversely, a list of 34 minerals has been established as occurring in only a single geographic origin. These inclusions therefore serve as particularly reliable markers for origin determination (Table 4).

Determination of Emerald Geographic Origin Through Solid Inclusion Analysis and UV-Vis-NIR Spectroscopy

The differentiation between low and high iron types makes certain solid inclusions particularly useful for identifying the geographic origin of emeralds (Figure 3). For instance, baryte (BaSO₄), a barium sulfate, is found in emeralds from Colombia, Madagascar, Russia, South Africa, and Zambia (Kafubu).
Among these, only Colombia is classified as low iron, making baryte, when associated with a low iron UV-Vis-NIR spectrum, a strong indicator of Colombian origin. Similarly, galena, a lead sulfide, observed in both Colombia and South Africa, helps support origin determination through iron-type comparison.
The Davdar deposit in China exhibits fluid inclusions similar to those found in Colombian emeralds, along with a low iron UV-Vis-NIR absorption spectrum (Saeseaw et al., 2014). However, hematite (an iron oxide) and scheelite have only been identified at Davdar or in high iron localities (Schwarz and Curti, 2020). In Afghanistan, emeralds, also of the low iron type, are distinguished by the presence of rutile (a titanium oxide) and tremolite (an amphibole), two minerals otherwise found only in high-iron sources, thus reinforcing their diagnostic value.

Conclusion

The results confirm the value of combining solid inclusion identification with UV-Vis-NIR absorption spectroscopy for determining the origin of emeralds. Analysis across a wide geographic range led to the identification of 34 minerals found to be related to only one deposit, making them strong indicators of geographic origin. In contrast, minerals such as quartz, calcite, or apatite, although frequently observed, have low discriminative value due to their widespread presence across numerous deposits.

Limitations

Geographic origin determination of emeralds relies heavily on identifying inclusions, which reflect the local geology and host rock characteristics of specific deposits. However, this must be combined with trace element analysis and spectroscopic properties, since relying solely on one criterion poses significant risks of misidentification.

Further Research

Not all inclusions are identical, even when found across multiple deposits. Variations in their size, shape, and edges may provide additional criteria for distinguishing emeralds by prove-nance. Quantification of solid inclusions in these emeralds is currently under investigation.

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The book Emerald: Modern Gemmology is the first one to take a comprehensive look at emerald since the 1981 publication of Sinkankas’ Emerald & Other Beryls. Several fine volumes have been published in the interim: Ronald Ringsrud’s love letter, Emerald: A Passionate Guide (2009); Peretti & Falise, Magnificent Green: Emeralds of Pakistan, edited by Kazmi and Snee (1989); and Kris Lane’s excellent historical study of Colombian emerald, The Colour of Paradise (2010). Other than Kasmi and Snee, a highly technical work, the other books mentioned could be termed extended monographs on emeralds from a single source—Colombia.

Emerald: Modern Gemmology takes a comprehensive gemological look at emerald from twelve countries: Afghanistan, Brazil, Colombia, Ethiopia, Madagascar, Nigeria, Pakistan, Russia, Tanzania, Zambia, Zimbabwe, and China. These are all important sources. All have either produced commercial quantities of emerald during the past several decades or have the potential to do so in the future.

In his Foreword, Professor Schwarz points out that the main job of the modern gemological laboratory is to determine country of origin. Given the many thousands, sometimes hundreds of thousands, dollars riding on a laboratory cert, the ability of a lab to get it right is a game played for very high stakes. The main thrust of the book is devoted to a discussion of the criteria necessary to
make an accurate determination of geographic origin. Another of the laboratory’s important jobs, the determination of the presence, type, and degree of artificial treatments—a particular thorny issue—is, unfortunately, not part of the discussion.

The book is primarily aimed at the professional gemologist. The authors distinguish between the traditional and the modern approach. Country of origin determination began with the work of Professor Eduard Gübelin in the 1950s and focused almost exclusively on inclusion study. This, Professor Schwarz calls the traditional method. Since then, the issue has become decidedly more complex.

In Chapter I, the authors begin by breaking down the modern approach to gathering the necessary gemological information into six steps or criteria: Chemical Fingerprinting, Internal Features (which remains the single most important study), Spectral Fingerprinting, Vibrational Fingerprinting, Isotopic Fingerprinting, and Physical-Optical Characteristics. The first four chapters provide a detailed overview of these six steps. The following twelve chapters discuss these criteria as they apply to deposits country by country.

I found the discussion of chemical fingerprinting in Chapter I of particular interest. The chemical trace elements found within a particular stone are reflective of the geological environment of the stone’s formation. Thus, the relative concentrations of these elements are extremely important factors in geographic origin determination. The authors discuss the various geological environments and provide graphs showing how the relative concentrations of elements necessary for origin determination, such as chromium, vanadium, and cesium, overlap in gems from various locations.

The section of isotopic fingerprinting will be of particular interest to historians and archaeogemologists. An article published in 2000 in Science magazine caused a minor sensation when measurement of the oxygen isotope in emeralds, with proven ancient pedigrees, demonstrated that one “Old Mine” emerald—thought to be of Colombian origin—was actually a Swat Valley gem, proving that this valley was an active mining area much earlier than previously thought. A very useful figure in Chapter I breaks down the relative oxygen isotope composition of emerald from historically important sources including the old Egyptian and Austrian mining areas.

The discussion of internal features, the traditional approach to origin determination, is discussed, in detail, in Chapter II. Inclusion study remains the most important single criterion and this discussion takes up by far the most space in the book. The text is enhanced by numerous color photomicrographs illustrating the various features discussed.

Chapter III, Geological-Genetic Considerations, discusses timescales of the formation of emerald types based on a scheme developed in 2019 (Giuliani et al.). This section is sumptuously illustrated with excellent photographs of mines and geological strata.

Chapter IV, Geographic Origin Determination, discusses its possibilities, methods and limitations.

Each of the later chapters draws a detailed portrait of emeralds from one of the twelve countries. The authors systematically cover the six evaluation criteria in each chapter. Each begins with a onepage history of the deposit plus a lovely graphic of the location along with cartoons outlining the geology of the mining area. The last section of each is a photographic gallery of inclusions specific to the area.

The inclusion gallery photography, by Theodore Rozet and Martial Curti, is particularly well done. The images are sharp and well-focused and very useful for origin determination in the lab or in the field. Both photographic technology and color reproduction in print have made several leaps forward in recent years and those improvements are readily apparent in this beautifully produced volume.

The book includes an extensive bibliography, which suffers somewhat from the failure to list all references by primary author. The lack of both an assertion of copyright as well as a publication date are minor annoyances.

Sumptuously produced, Emerald: Modern Gemmology is an extremely important book. Reviewers typically say that a book is a “must have.” In this case, the words are not mere hyperbole. It is an essential volume for every serious gemologist. The book has been produced in a limited-edition of just 1000 copies. It would be advisable, therefore, to place your order immediately.

• Colombia – New Realities in the Emerald Industry
• About InColor Magazine
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• The Smithsonian National Gem Collection – Unearthed
• East Africa – Mining and Rough Supply

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