This study examines sapphires naturally enriched in high-field-strength elements (HFSE) from metamorphic origins in Sri Lanka and Madagascar. These sapphires display distinctive chemical inhomogeneities and microscopic growth features, as well as variable FTIR spectra, often including a broad absorption band near 3300 cm–1. Some of the studied samples also show FTIR spectral characteristics and short-wave UV luminescence typically associated with heat-treated stones, although all were unheated. Our findings demonstrate that commonly used indicators—such as specific FTIR band patterns (mainly the 3309 cm–1 triplet) and chalky bluish white short-wave UV fluorescence—are not always reliable for identifying heat treatment. Accurate distinction between heated and unheated sapphires requires detailed microscopic examination combined with advanced trace-element analysis and spectroscopic techniques, including Raman micro-spectroscopy of inclusions such as zircon, goethite and diaspore.

gems, corundum, treatments.4, Sri Lanka.12, Madagascar.12, heat treatment, FTIR

Although the emerald deposits in India and the Himalayas were not officially discovered before the 20th century, recent gemological analyses conducted by the LFG (French Gemological Laboratory) on emeralds from historical jewelry dating back to the 16th century have shown that they correspond to the characteristics of the Swat deposits (Pakistan). This discovery is consistent with ancient gemological literature, which, since Theophrastus (4th century BCE), mentions the Himalayas as a source of emeralds. This interdisciplinary article explores the methodological difficulties inherent in historical gemology and highlights the importance of scientific gemology for art history and archaeology.

gems, beryl, emerald, Afghanistan, Egypt, Colombia, history of gemology, Central Asia, China, Tajikistan, Pakistan

Many important works of ancient literature have been translated many times over the centuries, perhaps none more so than Pliny the Elder's Natural History. Because classical writers did not follow conventions of objectivity or citation remotely similar to modern standards, understanding the literary context is important when trying to extract factual information. The perspective of a translator also shapes how modern readers interpret an elusive original meaning. Older translations are well known for distorting the meaning of a word or passage when the text is unclear. Translators sometimes imposed their own contemporary knowledge on the past-knowingly or not. This was especially common when they lacked subject expertise, misread corrupt (damaged) texts, or failed to grasp the literary genre, for example, interpreting poetic rhetoric as an objective description of physical things, as in technical writing. The task becomes more difficult when ancient words have no direct equivalents in modern languages. The following essay explores some of the challenges of technical writing about gems from the Hellenistic to Roman periods (323 BCE to-2nd century CE), with a focus on Book 37 of Pliny's Natural History, written in the 70s CE. It contains the richest vocabulary in classical literature for describing gemstones, including their names, colours, and visual properties. Although these terms do not always correspond with modern gemmological classifications, there are notable overlaps that can help identify some minerals whose identity might otherwise remain unclear.

gems, history of gemology,

This article traces the development of the modern gemmological laboratory from 1925 to the present day, a 100-year journey that has seen not only a gradual and then explosive evolution in the application and maturity of the science, but also importantly the standing that gemmological laboratories have enjoyed within the gemstone industry and the scientific community. The passionate people involved have made tremendous contributions to the understanding of gem materials, and their willingness to embrace the latest technology and attract successive generations to the field has made the study of gem materials within gemmological laboratories one of the most exciting theaters of life.

gems, gemology, advanced gemology, gem testing, history of gemology, gem lab

Throughout the history of gemology, quartz has been a main target of gemological microscopists. A detailed study of the wide variety of inclusions in quartz is as complex an earth-science related mental exercise as any gemologist would ever undertake. This is not surprising, as quartz occurs in a wider range of geologic environments than any other mineral species, and the inclusions it holds testify to this. The photomicrographs, pictured here with this study, provide the reader only a glimpse at the micro-world of quartz beyond rutile.

gems, photomicrography, inclusions, quartz, chalcedony, agate

A puzzle, almost as old as the modern science of gemology itself, concerns metamorphic minerals such as garnet and corundum that normally crystallize in an opaque, stony manner. Under rare circumstances, however, such minerals crystallize as transparent gems. Why should that be? An area in the Kenyan-Tanzanian border region provides clues to why, where, and when gem-quality crystallization occurs. Higher than usual temperature at depth permits metamorphic minerals to crystallize at shallower levels. and thus with less than usual constraining pressure, hence potentially as transparent gems. A source of short-lived excess heat in the Penny Lane area (Kenyan-Tanzanian border) is furnished by friction produced by nearby thrust faults.

gems, geology, East Africa, Gondwana, Detrital zircons, Tectonics, Cambrian Explosion, John Saul, Penny Lane, ruby, Kenya

This article is a brief survey of the historical methods of describing and assessing the quality of coloured gemstones, tracing these from ancient times to the end of the 18th century. Examining historical texts and inventories reveals how features and flaws of gemstones were observed and used to determine their value. This article considers various historical periods, including the ancient world, the medieval Muslim world, early India, and medieval Europe, highlighting the changing criteria and expertise involved in gem judgement. This study demonstrates the historical depth of gem connoisseurship and its influence on modern gem assessment practices.

gems, gem trade, gem appraisal, jewelry appraisal, valuations, history of gemology

During the Qing Dynasty (1644–1911), court artisans carved agates with a high degree of technical ability and inventiveness. Agate wares produced during the reign of the Yongzheng (1723–1735) and Qianlong (1736-1795) emperors exploit the full breadth of chromatic effects and degrees of translucency offered by these silicate stones. During this period, agate carvings were produced in high numbers, and imperial commissions made conscious use of the stone's unique material qualities. Because the geological environment in which agates are formed affects their pigmentation, the range of agate colors recorded in historical documents and seen in surviving objects reflects a variety of geographical origins. This paper considers how agates were understood by scholars and appreciated by emperors at a time of territorial expansion and interest in new minerals.

gems, quartz, agate, chalcedony, agate carving, China, Qing Dynasty, Qianlong

In Gems and the New Science, Michael Bycroft argues that gems were connected to major developments in the “new science” between the sixteenth and nineteenth centuries. As he explains, precious and semiprecious stones were at the center of dramatic shifts in natural knowledge in early modern Europe. They were used to investigate luminescence, electricity, combustion, chemical composition, and more. They were collected by naturalists; measured by mathematicians; and rubbed, burned, and dissolved by experimental philosophers. This led to the demise of the traditional way of classifying gems—which grouped them by transparency, color, and locality—and the turn to density, refraction, chemistry, and crystallography as more reliable guides for sorting these substances. The science of gems shows that material evaluation was as important as material production in the history of science. It also shows the value of seeing science as the product of the interaction between different material worlds. The book begins by bringing these insights to bear on five themes of the Scientific Revolution. Each of the subsequent chapters deals with a major episode in early modern science, from the expansion of natural history in the sixteenth century to the emergence of applied science early in the nineteenth century. This important work is not only the first book-length history of the science of gems but also a fresh interpretation of the Scientific Revolution and an argument for using a new form of materialism to understand the evolution of science.

gems, gemology, history of gemology, gem testing, Great Britain, FGA, London

Cevâhirnâmes are significant scientific and cultural texts within the Islamic intellectual tradition, particularly during the Ottoman period. Precious and semi-precious stones were valued not only for their aesthetic and economic importance but also for their perceived medical and therapeutic properties. Numerous works titled Cevâhirnâme were produced to describe the origin, classification, physical and chemical characteristics, and healing qualities of these stones. One of the most important examples of this tradition is the Cevâhirnâme-i Abdülmecid-i (Guidebook), compiled in 1857 by Chief Physician Salih Efendi under the patronage of Sultan Abdülmecid. Considered the first systematic gemological study in the Turkish-Islamic world, the work represents one of the final examples of the classical cevâhirnâme tradition. The book consists of twelve chapters devoted to stones such as diamond, ruby, emerald, pearl, turquoise, amber, coral, agate, and jade, examining their physical properties alongside their temperaments (mizaj) and effects on the human body. By combining traditional humoral medicine with empirical observations of gemstones, the Cevâhirnâme-i Abdülmecid-i serves as a valuable historical source that bridges traditional Islamic medicine and early modern gemology, reflecting the scientific, medical, and cultural knowledge of the late Ottoman period.

gems, history of gemology, Arabic mineralogy, gem prices, corundum, ruby, sapphire, diamond, emerald, pearl, turquoise, amber, coral, agate, jade

This book is basically a retrospective of the writings/musings of John Saul, the noted geologist who discovered the John Saul ruby mine in Kenya. These essays touch on the great questions of Origins. The human adventure began when people first started to share complex ideas. A very early set of shared ideas provided a reasoned scheme that was both religious and scientific that would enable souls to take the Milky Way to the domain of the immortal gods. Other essays present cancer as originating when damaged tissues lose control over individual cells. Liberated cells multiply and may vary in ways that are incompatible with the functioning of multi-celled creatures, of humans in particular. Cancer first emerged during the Cambrian Explosion itself. Four essays discuss the survival of deep terrestrial impact-scars akin to those on the Moon, but far less easy to see. Such scars provide our planet's initial conditions. Fractures on the rim-zones of the scars guide plate tectonics and the deposition of minerals, and are implicated in at least one mass extinction.This book touches on little-discussed aspects of prehistory, history, the explosion of life during the late Precambrian, cancer research, and regional geology. Saul's writings and ideas represent some of the most original in the field of gemology, tying together not just the origins of gems, but the origins of human civilization itself. Highly recommended!

gems, geology

Describes the appearance of a 3232 FTIR peak in a pink sapphire from Madagascar that appeared to be unheated. This peak is typically associated with gems that have been heat treated.

gems, corundum, treatments.4, heat treatment detection, FTIR, 3232

Determining the geographic origin of Cu-bearing tourmaline poses a significant challenge in gemmology, particularly when traditional microscopic methods yield inconclusive results. This study applies a combined analytical and computational approach using 469 gem-quality samples from Brazil, Mozambique, and Nigeria. A total of 57 elements (from Li to U) were quantified using full-mass-spectrum LA-ICP-TOF-MS. The high-dimensional elemental dataset was reduced to interpretable 2D maps using non-linear unsupervised machine-learning algorithms, including t-distributed stochastic neighbour embedding (t-SNE) and uniform manifold approximation and projection (UMAP). These methods successfully identified complex patterns and distinct subgroups, revealing compositional similarities not captured by traditional linear approaches. The resulting clusters provided a clear framework for geographic origin determination of unknown samples. Elemental signatures of key elements (i.e. Na, Ca, Li, Ti, Fe, Mn, Cu, Ga, Sr, La, and Pb) highlighted their influence on clustering and related geochemical variations to colour and geographic origin. Unsupervised machine-learning algorithms do not rely on predefined origin labels. This reduces errors caused by uncertain origin information and helps reveal statistical outliers that may point to new or undocumented sources. By integrating colour information with compositional clustering, the method also provides a possible framework for identifying heat treatment in high-clarity stones.

gems, tourmaline, cuprian tourmaline, tourmaline heat treatment, Paraíba tourmaline, Brazil, Nigeria, Mozambique

The medieval Imperial Crown of the Holy Roman Empire preserved in the Imperial Treasury in Vienna, Austria, has been the focus of an ongoing study (e.g. Nasdala et al. 2023). Here, we report on geographic origin determinations of its gems, which can offer new insights into the gem trade of the Early and High Middle Ages. We examined the 172 gemstones and 233 selected pearls in the crown using a combination of high-magnification digital microscopy, μ-EDXRF analysis, and UV-Vis-NIR spectroscopy with mobile instruments. The gemmological characteristics of most of the sapphires (including four stones over 100 ct) were consistent with a Sri Lankan origin. Most of the almandine and pyrope garnets were from South Asian deposits, while the emeralds were attributed to Egyptian sources, except for two from Swat, Pakistan. All these deposits have likely been exploited since Antiquity. Several stones, including three antique amethyst intaglios, were reused antique gems. The two spinels on the front plate of the circlet came from Kuh-i-Lal in Tajikistan, and six small (< 1 ct) basalt-related sapphires may have originated from deposits in France. Six faceted sapphires with steep, four-sided, and trigonal pyramids mark the onset of faceting of hard gemstones. The pearls were predominantly of saltwater origin from the Indian Ocean, but a significant number were most likely European freshwater pearls. The assemblage of gem materials in the crown’s removable arch and cross suggests that they are of later manufacture than the circlet.

gems, corundum, quality.10, crown jewels, auction, diamond, pearl, beryl, emerald, spinel, Tajikistan, Kuh-i-Lal, Swat, Pakistan, France.12

Recent field observations in Pakistan have revealed that specimens circulating in local gem markets and near mine sites have increasingly been artificially assembled or altered. Local dealers and prospectors from the Hunza and Gilgit mining areas offered “Frankenstein” specimens, pieces assembled by gluing together fragments of crystals and host rock (figure 6). While adhesives can sometimes be seen under magnification, many joints are subtle enough to mislead buyers or tourists. Crystals such as aquamarine are often skillfully mounted onto matrices to imitate natural specimens, with some pieces further polished, dyed, or even oiled to enhance their appearance (figure 7). In certain cases, resins mixed with crushed marble or host rock are applied, making detection even more difficult. For example, in Peshawar’s Namak Mandi gem market, a ruby reportedly from Jegdalek was identified as a synthetic crystal mounted on natural host rock. In addition to this deceptive practice of adhering specimens to host rock, broken specimens are also repaired with adhesives, often without disclosure. With time, the quality of assembly is improving, making detection more challenging. The close proximity of these reconstructed specimens to the mines is a reminder that “from the mine” does not automatically guarantee authenticity. Collectors and gemologists should be aware that stones described as directly sourced may have undergone significant human intervention. Similar practices are common in neighboring regions, including Afghanistan.

gems, corundum, ruby, Pakistan.12, assembled stones.8, beryl, emerald, assembled specimens

Recently, a carved green snuff bottle was submitted as jadeite jade for identification at the Taiwan Union Lab of Gem Research (TULAB) (figure 1). The surface of the bottle displayed a white matrix with dense mottled green areas. A spot refractive index was approximately 1.68–1.69, which was noticeably higher than the typical range of values for jadeite jade. However, such results may occur if jadeite contains kosmochlor. Under microscopic observation, the surface of the carving revealed a white matrix with green patches (figure 2). Interestingly, these green patches appeared red when viewed through a Chelsea filter. To further identify the material, Raman spectroscopy (785 nm laser) was performed and compared with the RRUFF database (B. Lafuente et al., 2015, https://rruff.info/about/downloads/HMC1-30.pdf). The results indicated that the white matrix was dolomite, while the dark green patches were muscovite (figure 3). With the assistance of energy-dispersive X-ray fluorescence (EDXRF) analysis, the green portions were confirmed to be fuchsite (chromium muscovite). All testing indicated that the snuff bottle was composed of a dolomite aggregate with fuchsite. Although its appearance resembled jadeite jade, the bottle’s refractive index and Chelsea filter reaction clearly distinguished it from jadeite jade. Raman spectroscopy and EDXRF were used as more precise methods to confirm the material, which appears to be a new jadeite simulant that has recently appeared on the market.

gems, corundum, geology.11, Burma.12, Mogok, beryl, emerald, Russia, Malysheva, Ural Mountains, alexandrite, chrysoberyl, pegmatite

It is widely recognized that some gem minerals often occur together in various localities—either in the same host rock or in the same deposit. Gem minerals each require a certain set of physical and chemical conditions for their formation. This edition of the Colored Stones Unearthed column will explore where specific gem minerals are found together and the conditions that produce these distinct geological settings.

gems, corundum, geology.11, Burma.12, Mogok, beryl, emerald, Russia, Malysheva, Ural Mountains, alexandrite, chrysoberyl, pegmatite

In 2017, the first emerald deposit in the Qinling Orogenic Belt was found in Zhen’an County, Shaanxi Province, China. This study presents a comprehensive analysis of the gemological, spectroscopic, and trace element characteristics of a select set of Zhen’an emerald samples based on standard and advanced gemological methods, including gem microscopy, ultraviolet/visible/near-infrared spectroscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, and laser ablation–inductively coupled plasma–mass spectrometry. Microscopic studies revealed that Zhen’an emerald exhibits longitudinal striations and inclined growth steps on its hexagonal prism faces and contains an abundance of two-phase (gas/liquid) fluid inclusions. A variety of mineral inclusions were identified, including phlogopite, plagioclase, scheelite, calcite, talc, and hematite. Some crystals display color zoning, with a deeper green rim containing elevated vanadium and iron. Zhen’an emerald’s dominant chromophore is vanadium, and the material is characterized by a high vanadium concentration, notably low chromium, a moderate iron concentration, and an elevated ratio of gallium to cesium. These unique geochemical signatures of Zhen’an emerald, along with their internal features, could be a robust tool for discerning emerald from this deposit.

gems, beryl, emerald, China, Zhen'an, Shaanxi

Sapphires have been mined in Montana since being discovered at Eldorado Bar, along the Missouri River, in 1865. The most valuable gold deposit in the area was mined near the top of the French Bar complex from 1867 to 1869. On portions of the Virginia terrace and the Center terrace, the French Bar sill, which sparsely contained sapphires in a host rock—identified here as a basaltic trachyandesite, but described elsewhere as a minette—was reported by Kunz in 1891. Other than Yogo Gulch, where the sapphires are in a lamprophyre dike, the French Bar sill is Montana’s only other source of gem-quality in situ sapphire. New ownership of the property in 2020 has resulted in the largest production to date, although it is still sparse. In this study, the authors examined 80 French Bar sill sapphires in matrix; 16 sapphires removed from the matrix, ranging from very small to 17.99 ct; 4 faceted stones; and 5 partly polished crystals. Trace element chemistry and inclusions were consistent with—and generally indistinguishable from—faceted Montana sapphires from the secondary deposits of the Missouri River, Rock Creek, and Dry Cottonwood Creek. This indicates that while the magmatic material (Eocene volcanism) that transported the sapphires from deep within the earth was different in certain cases, such as with French Bar sill, the genesis of the sapphires may be the same or similar. Many of the surface resorption features are similar, but one important distinction exists. Around 25% of Missouri River alluvial sapphires have encrustations of spinel, likely a result of reaction during transport by a mafic magma. Primary French Bar sill sapphires always have an encrustation of biotite (phlogopite) mica, but never spinel. The French Bar sill itself is certainly too small in extent to have supplied all the alluvial sapphires found at the Missouri River.

gems, corundum, USA.12, Montana.12, Missouri River, French Bar, Eldorado Bar, sapphire, geology.11

The 3161 cm⁻¹ infrared (IR) band can be observed in variously colored natural corundum, most commonly in yellow sapphire. The presence of this feature is used frequently as supporting evidence to conclude that a sapphire has not been heat treated (C. M. Breeding and N. J. Ahline, “Infrared spectroscopy and its use in gemology,” Winter 2024 G&G, pp. 474–492). This 3161 cm⁻¹ band is often present with other less intense side bands known as the “3161 cm⁻¹ series” and includes features at ~3355, 3242, 3100 (shoulder), 2460, and 2420 cm⁻¹ (C. P. Smith and C. van der Bogert, “Infrared spectra of gem corundum,” Fall 2006 G&G, pp. 92–93). The exact origin of the 3161 cm⁻¹ band is not well understood, although it is thought to be related to stretching vibrations of hydroxyl groups caused by interstitial H⁺ ions present as charge compensation for Fe²⁺ substituting for Al³⁺ in the corundum structure (M. C. Jollands et al., “Vibrational properties of OH groups associated with divalent cations in corundum (α-Al₂O₃),” European Journal of Mineralogy, Vol. 35, No. 5, 2023, pp. 873–890).

gems, corundum, color.4