This content was first published on IGR – Italian Gemological Review no. 19 in 2024. The information provided here is therefore current as of the original publication date.
The Sixth National Conference on Diamonds and Colored Stones was held in Turin, Italy, at the Aula Magna of the Department of Life Sciences and Systems Biology on July 8 and 9, 2024.
Under the coordination of Prof. Mario Tribaudino, Prof. Alessandro Pavese and Prof. Emanuele Costa, with the active collaboration of Raffaella Navone, long-time collaborator of the IGR, the event had the title “Diamonds and precious gems: Gem Identification in the Age of Artificial Intelligence”.
Artificial Intelligence and gemology
Although the Conference in Turin was completely free of charge, attendance was lower than the 2023 edition, maybe because of the date. Despite the lack of simultaneous translation, the presentations were well received and only one presentation from remote was given in English.
The complex subject of Artificial Intelligence (AI) was discussed in Turin by two of the twenty-eight speakers involved. It is worth coming back to it in the future since it is agreed upon on the fact that is the latest challenge affecting all fields of scientific research, changing horizons and perspectives, and this will undoubtedly influence the future of gemology. Peter Tollan (Gübelin Gem Lab) foreshadowed this as early as in the 2022 Conference in Ferrara(1), highlighting the numerous sophisticated applications focused on origin identification that the laboratory of Gubelin has developed and reported by IGR(2).
Alberto Oddenino (University of Turin; Pavesio & Associati) gave a conceptual overview of AI, mainly from a legal perspective. He illustrated the changes that have become structural in today’s world, which is increasingly defined by the use of AI. This development is rightly considered the fourth revolution, following the Copernican, the Darwinian and the psychoanalytical revolutions.
Before reaping the computational benefits, those working with AI must recognize the risks associated with technological pervasiveness, the reduction of reality to data, and the fact that legal frameworks lag behind technical applications. However, such considerations venture into ethical and epistemological dimensions, whereas gemologists are fundamentally more practical. Troy Blodgett (GIA researcher) presented a pragmatic approach to AI, emphasizing that it is not a magic solution to all laboratory analytical challenges. Instead, AI can significantly improve shape classification (resolving borderline cases: oval/modified-marquise/marquise), facet analysis, and clarity grading through neural network and siamese training. In addition, gemologists can “label” data and train AI to detect and classify inclusions.
Gemology and regulations: an overview of KP, CITES, LMHC requirements, and traceability
More substantial than the discussions on AI that gave the event its title were the five presentations that focused primarily on practical experiences related to regulatory compliance for gemstones. Claudia Zedda, Daniela Montaldo and Rebecca Traverso (Customs Agency of Turin) highlighted the instrumental resources of the Chemical Laboratory of the Customs and Monopolies Agency of Turin and its role as the Italian focal point for Kimberley Process (KP) compliance. The KP is a complex and controversial intergovernmental cooperation mechanism(3) that implements a certification scheme (KPCS) to combat the illegal import/export of rough diamonds. The EU adheres to it with a single membership for 27 member states. Most of the imported material is routed to Antwerp. Customs control (integrity and weight verification, witnessed parcel opening, invoice compliance, value control) takes place in any EU country with a designated office (Italy has one, France does not).
Lieutenant Colonel Cristian Cretaro and Captain Chiara Massoli (CITES Unit of the Carabinieri in Turin and Alessandria) described how CITES is operated. CITES is an international convention, incorporated into national legislation since 1975, for the protection of 40,000 endangered animal and plant species. CITES consists of three appendices: Appendix I (endangered species, trade prohibited); Appendix II (species not threatened with extinction, but with limited trade); Appendix III (species protected by individual states to regulate exports from their territories). Ivory from proboscideans (elephants, of which tens of thousands are killed for the illegal trade) and non-proboscideans (hippopotamus, narwhal, walrus) is strictly excluded from all national and international transactions (Appendix I)(4). An exception is made for fossil mammoth ivory, a genus with several extinct species, identifiable by X-ray spectrophotometry and external Schreger lines (elephant lines exceed 90°). In Italy, the possession of ivory is only allowed for personal use, provided it was declared before 1992.
Another gem sensitive to CITES restrictions is coral. While Mediterranean Rubrum is part of Appendix II, Elatius, Japonicum, Konojoi and Secundum are listed in Appendix III at China’s request and are therefore not exportable.
Antonello Donini (Cisgem Milano) presented the 14 copyrighted information sheets of the LMHC, an organization founded in 2001, following the path set by Intergemlab in 1986, bringing together seven laboratories: CGL (Japan), CISGEM (Italy), DSEF (Germany), GIA (USA), GIT (Thailand), Gübelin Gem Lab (Switzerland), and the SSEF Swiss Gemmological Institute (Switzerland). The sheets cover issues related to corundum (with or without heating indications, with heating residues in fissures and/or cavities healed and/or filled with glass, clarity enhancement, deep diffusion of foreign elements other than hydrogen, padparadscha), emerald (fissure filling/clarity enhancement), Paraíba tourmaline, alexandrite, jade, amber and copal, hydrophane opal. The purpose of the sheets is to harmonize nomenclature and eliminate potential discrepancies on controversial gemological topics.
Rocco Gay (Petramundi), drawing on his direct experience as an importer and manufacturer of stones, provided interesting insights on the topic of traceability. Certified control of the integrity of various supply chain stages is now a non-negotiable requirement for major jewelry brands. For example, Afghan lapis, materials from Russia and Afghanistan, Burmese rubies, and Congolese malachite (if purchased before 2024) are practically banned.
For colored stones, the fragmented supply chain presents many more challenges than for diamonds, which can benefit from dedicated blockchain systems. Direct control back to the mines is limited, as the material is often intermediated. On the other hand, relying on multinational mining companies (Gemfields, Fura Gems, etc.) would encourage a phenomenon of “economic colonialism”. ICA and RJC are the most accredited bodies to support companies on their way to responsible sourcing.
Ancient gems, very ancient gems
The archaeogemmological horizon inspired Loredana Prosperi’s (Istituto Gemmologico Italiano) lecture, which focused on the characterization of some gems from the rich collections of Roman Pompeii. Among the notable finds were numerous agates and carnelians, saltwater pearls (with manganese detected), a citrine quartz with tiger-striped inclusions, possibly caused by heating after the eruption, a blue corundum of magmatic origin weighing about 11 carats with an engraving of a winged horse, full of inclusions and probably of Ethiopian origin, and a green chalcedony known as prase, the “emerald” of the Romans.
In a historical context, Ugo Longobardo described the gems of the Treasure of Sant’Agata in Catania, while Marilisa Yolanda Spironello (University of Catania) provided a gemological account of Sicilian liturgical furnishings and ex-votos.
A much more significant leap into the past was proposed by Fabrizio Nestola (University of Padua), who studied super-deep diamonds, formed between 3.5 and 0.2 billion years ago at depths ranging from 140-150 km to as much as 1,000 km, reaching the lower mantle. They represent only 1% of all diamonds studied to date. These diamonds are particularly intriguing because they provide extremely valuable information about the Earth’s deep interior. When these rare and precious stones trap mineral inclusions as they rise to the surface, they deliver actual fragments of the deep mantle right into our hands. In addition, famous diamonds such as the Cullinan and the Hope Diamond are super-deep diamonds.
Origin determination. Ruby and lapis
Two presentations highlighted the issue of identifying the geographical origin of gemstones, which is now so controversial and crucial for guiding studies and directing gemological research. Since previous Conferences in Italy, many insiders believe that Italian gemology should provide academic research with a better support to obtain comprehensive characterizations of the materials produced by industry and valued by the market. It is essential to organize a systematic collection of samples of those gems whose market value is enhanced by the determination of their geographic origin, with the support of those familiar with the mining areas.
The accidental discovery at the University of Ferrara of an unclassified group of rocks, which turned out to be of metamorphic origin from deposits in West Africa or Madagascar, gave Costanza Bonadiman (University of Ferrara) the opportunity to establish the relationship between the environment in which the mineral was formed and its chemical-physical properties. To study the causes of corundum colors related to chromophoric elements (pink, red: trivalent Chromium Cr3+; orange: Cr3+; yellow: trivalent Iron F3+, blue: bivalent Iron Fe2+ – tetravalent Titanium Ti4+; green, violet and blue: trivalent Vanadium V3+), it is necessary to associate the behavior of three silicon Si isotopes (28Si, 29Si, 30Si), which show significant interference. For example, Chromium, which produces red and violet, can be enhanced or diminished by Silicon. However, since its levels are relatively constant in most rubies (between 500 and 1400 pp), Si is less suitable as a fingerprinting tool. Consequently, the investigation focused on the other five elements: Vanadium V, Iron Fe, Gallium Ga, Chromium Cr and Titanium Ti. Of these, V, Fe and Ga are considered the most independent variables for determining the rock fingerprint.
Laura Guidorzi (University of Turin) presented the results of a study started in 2008 by the University of Turin on the chemical-physical characteristics of lapis lazuli, a metamorphic rock with 30 phases, originating mainly from the Badakhshan deposits in Afghanistan, with the possible existence of other minor sources in Asia (and other trade routes). A non-invasive protocol was developed to identify five sources: Afghanistan, Tajikistan, Siberia, Chile, and Myanmar. Tests include microscopy and advanced techniques such as PIXE and ionoluminescence, which are only available in large research facilities.
Characterization and treatments: Libyan glass, pink and blue opal, trapiche, amber, tourmaline, topaz and turquoise
Pia Antignani (Labigem Vicenza) has traced the history of Libyan Desert Glass (LDG), which was formed some 29 million years ago as a result of either the impact or the atmospheric explosion of an extraterrestrial body. In 1922, archaeologist Howard Carter discovered a yellow-green scarab among more than 5,000 artifacts in the tomb of Pharaoh Tutankhamun. It was not until decades later that Italian mineralogist Vincenzo de Michele identified the artifact as natural glass. The study now provides a complete characterization of LDG using advanced techniques such as SEM-EDS, FTIR, micro-Raman, and UV-Vis-NIR.
Franca Caucia (University of Pavia) reported the results of the characterization of gem-quality pink opal from an Australian deposit in the Lower Cretaceous Windalia radiolarite formation. The study, conducted on rough and cabochon samples using a multi-technique protocol (invasive: XRPD, SEM-EDS, laser ablation-ICP-MS; non-destructive: micro-Raman, FTIR/micro-ATR, UV-Vis-NIR, microfluorescence), revealed that this rare and little known opal ranges from translucent to opaque, with a greasy luster and shades ranging from light pink to deep pink, often with an orange overtone.
Sara Monico (University of Milan) characterized blue Andean opal from the Acarí mine in Peru, whose characteristic blue color is attributed to mineral inclusions rich in copper. The approach was multimethod: X-ray diffraction techniques allowed the reconstruction of the mineralogical composition and the quantification of the amorphous fraction, while Raman mapping highlighted the different silica phases and the distribution of impurities. Microstructural and trace element analysis indicate that the blue color is influenced by both mineralogical inclusions and geological and environmental processes of formation.
Isabella Pignatelli (University of Lorraine) shed light on the rare “trapiche” varieties, a Spanish term inspired by the resemblance of this texture to a gear used to crush sugar cane. Originally, it referred to a type of Colombian emerald formed in black shale altered by albitization and calcitization. The term was later applied to sapphires and rubies (from marble-associated deposits) with similar textures from Southeast Asia.
In emeralds, this texture is characterized by a central core surrounded by six crystallographically equivalent growth sectors (dendrites and sometimes overgrowth) resulting from variations in physicochemical parameters during crystal growth. Until now, trapiche textures have only been found in minerals with high symmetry: cubic for garnet, hexagonal for emerald, trigonal for ruby and tourmaline. Recent studies using computed tomography (CT) have provided new mineralogical and geochemical data, allowing comparisons of trapiche textures in emeralds and rubies and a reconstruction of their growth modes.
Maya Musa (University of Pavia) reviewed the different types of amber available on the market: natural, dating from 25 to 100 million years ago (Simetite, Rumeite, Dominican, Mexican, Baltic, Burmite, Canadian) and treated by hydrothermal reconstruction and neo-synthesis from powders (amber powder pressed with or without additives using a hydrothermal process, copal treated with a hydrothermal process). A “frosted glass” pattern indicates pressure from powders, red streams show the use of high temperatures, and the “sun spangle” effect is caused by sudden cooling. These materials are often not identified by gemological labs, creating a “gray” market. In gemology, the difference between amber and copal is traditionally determined by the polymerization process.
Federico Pezzotta’s (MUM Mineralogical Museum) presentation was perhaps the only one to bring the investigation back to industrial gemstone mining, considering materials that are particularly valuable in the trade. Pezzotta revisited what he reported at the Conference held in 2023 in Rome, about the Mavuco deposit in Mozambique, discovered in 2006, of elbaite tourmaline. While the Paraíba variety was the subject in Rome, this presentation focused on copper-bearing rubellite. The deposit is producing 200/300 grams per day of gem-quality material out of 200 tons washed, of which 10% is Paraíba, which is still the primary target. However, all the tourmaline is sold, nothing is left over, and the deposit produces rough stones in a wide variety of colors: red or pink (with touches of violet), green, green/yellow, and blue.
The market clearly prefers blue Elbaite with a slight greenish tint. Blue stones with a neon effect, visible from a distance, are highly valued as they seem to have their own light. Heat treatment is critical to achieving blue tones. While blue stones are not treated, green stones respond well and yellow stones are a risk, so precise orientation is essential. Red copper-bearing tourmalines can also change color when heated, turning to a light blue, similar to aquamarine, which can be classified as a tourmaline Paraíba.
The market also rewards rubellite. Therefore, stones with a strong red hue, without pink or fuchsia tones, may not need to be heated and can still gain solid appreciation in the trade.
Floriana Rizzo (University of Aldo Moro, Bari) carried out an in-depth study of the causes of color changes in irradiated and heat-treated tourmalines, working on samples from different pegmatitic geological contexts (Cruzeiro and Golconda, Brazil; Malkhan, Russia; Nuristan, Afghanistan). These samples were analyzed by comparing spectra obtained before and after the treatments. The results show that color variations can be correlated with changes in the valence states of Manganese Mn and Iron Fe. Specifically, electron beam irradiation caused oxidation of Mn2+ → Mn3+ and Fe2+ → Fe3+, resulting in darker colors in the samples. Subsequent heat treatments on the irradiated samples reduced Mn3+ → Mn2+ and Fe3+ → Fe2+, resulting in lighter and colorless hues.
Giuseppe Elettivo (University of Aldo Moro, Bari) placed irradiation in the historical context of treatments in general and focused specifically on topaz, whose color can be altered using electrons, gamma rays, neutrons, and X-rays. The research involved the characterization of topaz samples (from primary and secondary deposits in Tanzania, Mozambique, Madagascar and Brazil) before and after irradiation tests with electrons at LINAC in Frascati and with the DXRL beam line at the Trieste Synchrotron. In conclusion, UV-VIS spectroscopy will become a key technique for the identification of irradiation treatments, in particular for the diagnosis of induced blue color and for the assessment of potential risks due to the decomposition of certain elements in gemstones, thus ensuring the safety of those who wear them.
Valentina Gagliardi (Istituto Gemmologico Italiano) studied turquoise, a gemstone formed by the leaching of rocks containing copper, aluminum, iron and phosphorus. It has a fine texture resulting from its crystalline microstructure, obtained by the dense packing of crystals, which produces a highly valued waxy luster, while a more porous texture is less appreciated. Treatments such as impregnation with waxes or resins enhance the luster and reduce the porosity of the material. Among the treatments, the Zachery process is particularly difficult to identify, as there are still many uncertainties about how it is carried out. Fortunately, its identification is now easier through analysis of the chemical composition (the presence of potassium is a clear indicator) using advanced techniques such as FTIR and XRF spectroscopy, which allow these treatments to be detected and help distinguish authentic turquoise from imitations, which are often made with dyed magnesite, howlite, lazulite, and dickite. The latest “Chinese porcelain” treatment has never been found in any turquoise submitted to the laboratory.
Instrumentation: Raman, Infrared Photography, High Energy X-Rays
There were three presentations on Raman spectroscopy. Riccardo Tagliapietra (Renishaw S.p.A.) highlighted the capabilities of the company’s equipment, whose core business is in metrology, motion control, spectroscopy and precision instrumentation. Riccardo Brandiele (Metrohm), using two Metrohm Raman instruments (ʎ=532 nm and 785 nm) equipped with microscopes with different magnifications (20x and 50x), reiterated a capability already used in gemology: by comparing the intensity of peaks, Raman analysis can determine the origin of a stone, identify impurities and even determine the geographical origin of the material. Specifically, this tool successfully distinguishes natural red coral with carotenoids, which has a peak at 1500 cm, from imitations, as well as saltwater pearls from freshwater pearls and imitations. However, it should be noted that the separation of the genus Corallium as a whole has been possible for some time. In fact the challenge remains to identify the species using non-destructive techniques.
Lorenzo Pasetti (University of Parma) focused on the characterization of different tourmaline species using Raman spectroscopy, in particular analyzing the dependence of peak parameters on chemical composition, the distribution of elements within the unit cell and color changes. The advantage of this type of investigation is that it is non-destructive and can detect specific species. Despite several studies using Raman spectroscopy to characterize tourmaline species, a complete model relating Raman peak parameters to tourmaline composition is still lacking.
Emanuele Costa (University of Turin) reported on an infrared photographic technique applied to some amber specimens from the Simeto River, which allowed a particular transparency that allowed a more detailed study of certain internal features of the specimens.
By removing the filters from modern cameras with CCD sensors, which are sensitive to ultraviolet and infrared radiation, the spectral sensitivity is extended to between approximately 850 and 350 nm, allowing infrared photographs to be obtained simply by placing an IR filter in front of the sensor or lens.
Amber samples provided by the University of Palermo were photographed under UV light (365 nm) in both the visible and infrared to check for IR fluorescence. When the infrared photographs taken under visible light were examined, it was found that even very dark simetite amber samples showed remarkable transparency.
Raffaele Agostino (University of Calabria) demonstrated the possibilities of using a high energy X-ray source for a wide range of applications at the µTomo2 and SoftX experimental stations of the STAR infrastructure in Cosenza.
Its applications in the field of advanced microscopy and spectroscopy can support gemological studies. The work is still in its infancy, but seems to be promising: in imaging, it has been possible to obtain a three-dimensional microscopic X-ray of a prehistoric mosquito in amber, to highlight negative crystals in topaz, and to map the defect distribution in garnets.
Laboratory curiosities
The daily routine of a gemological analysis laboratory is not without unusual and curious — if not bizarre — cases that arouse interest. Raffaella Navone (R.A.G. Turin) reported on a sample of lonsdaleite, an allotrope of carbon with a hexagonal crystal lattice (hence its description as a “hexagonal diamond”), offered for sale for 40,000 euros, which turned out to be an agglomerate of corundum powder. A supposed zultanite purchased in Turkey was analyzed as a glass containing lead, praseodymium and neodymium, causing metamerism. An apatite sample showed a coating with resin-filled cracks.
Giulio Chiodi (Labigem Vicenza) reported on a ring from an 18th century shipwreck made of a silver-copper alloy, a gastrolith from a shrimp, and a quahog pearl found in a clam served with a portion of take-out spaghetti.
Notes:
Article by Paolo Minieri, published on IGR – Italian Gemological Review #19 – Autumn 2024.
