Stefanos KarampelasLFG · Laboratoire Français de Gemmologie
Stefanos Karampelas
Dr
Chief Gemmologist/Researcher
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Introduction
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Publications
Publications (108)
Corals and pearls are “organic gems” produced by living beings. These esthetic “biomineralizations” are attractive for their
color and the optical effects resulting from their structure.
Forty-five “emeralds,” formerly set in the coronation crown of Napoleon III, were studied using nondestructive mobile spectroscopic and gemological means. Adorned with emeralds, diamonds, and gold, the crown was created in 1855 by royal jeweler Alexandre Gabriel Lemonnier but dismantled in 1887 for the auctioning of the French crown jewels. Some of...
The present study is focused on the analysis of zircon inclusions found in pink to purple sapphires from Ilakaka (Madagascar) with an optical microscope, Fourier-transform infrared (FTIR), and micro-Raman spectroscopy in order to update previous knowledge and find insights to separate heated from unheated samples. In total, 157 zircon inclusions in...
The current paper gives an overview of the development of Raman spectrometry in gemmological laboratories. While before 1990s, no commercial gemmological laboratory possessed such an instrument, all larger international labs have acquired these instruments by now. The Raman spectrometer is routinely used for the detection of emerald fillers, HPHT t...
TRAPICHE-LIKE INCLUSION IN AN OBSIDIAN FROM JALISCO, MEXICO - A cabochon-cut obsidian from Jalisco, Mexico, shows two white spherulitic inclusions on the surface, one of which was sectorized into four domains, the other into six, thus simulating a trapiche structure. This article shows how a quick identification based on first impressions can be ov...
The study of gems in jewellery of the Roman period from known archaeological contexts may provide valuable information for the trading routes of gems in antiquity, the techniques of their manufacture and decoration, the popularity of certain gems or their relation to a specific type of jewellery. Moreover, by the correct identification of these gem...
Gem characterisation is an ever-increasing challenge, especially with hard-to-detect treatments and new demands regarding origin determination [...]
Due to their appealing colors, gem quality tourmalines, particularly the blue to green Cu- and Mn-bearing Li-tourmalines known as the Paraíba type, have been of significant interest since their discovery at the end of 1980s. At the same time, the demand of other similar colored tourmalines increased. Most Paraíba-type tourmalines belong to the elba...
A spectacular 42.54 ct faceted alexandrite belonging to the collection of the Mineralogy Museum of Paris School of Mines was non-destructively characterised for this report. This historical gem was exhibited in at least one exposition in Paris during the late 1870s and/or in 1880 before it was donated to the museum by lapidary Henri Garreaud in 188...
This article characterises, for the first time, a drop-shaped blue cabochon set in an important gold ring. It dates to the Roman period (before 260 CE) and was found inside an intact (unplundered) marble sarcophagus unearthed in Thessaloniki in 1929.
Characterisation of Green Coloured Gems of the Roman Period from the Collections of the Archaeological Museum of Thessaloniki, Greece
Study of inclusions in gems from secondary deposits can give valuable clues on the geologic (and sometimes geographic) origin of these displaced materials. For the present study, seven gem quality fancy-coloured sapphires from Songea, Tanzania, were selected with, rarely observed in these gems, garnet inclusions in order to better understand their...
In the present study, rough emerald single crystals and rough emeralds in the host rock from the ruins of Alexandria and from the Mount Zabargad in Egypt, preserved in the collection of the museum of the Ecole des Mines (Mines Paris—PSL) since the late 19th or early 20th century, are investigated. All samples were characterized by non-destructive s...
Emeralds were discovered at Lake Manyara, Tanzania, around the end of the 1960s, and the mine was active for about a decade. Since then, gem-quality samples have reached the market only sporadically (Thurm 1972; Schmetzer & Malsy 2011). Various inclusion minerals have been documented in these emeralds, such as phlogopite, talc, albite and possibly...
Nineteen green‐coloured gems adorning a cross‐shaped pendant from the end of 19th century, belonging to Einsiedeln Abbey (Switzerland), were examined using non‐destructive methods. Estimated weights of the gems are ranging from about 0.19 to 2.34 carats. Natural multiphase inclusions with jagged outlines were observed in all samples under optical m...
Corundum primary deposits in Greece occur in four locations: Paranesti in Drama and Gorgona in Xanthi, both belonging to the wider Rhodope Massif, as well as, Ikaria island and Kinidaros in Naxos island, both belonging to Attic-Cycladic Massif. Eight samples were examined with spectroscopic methods (FTIR, UV-Vis, EDXRF) in order to better character...
The attractiveness of natural and cultured pearls is related, in part, to their colour. Raman spectroscopy was applied to natural and cultured pearls and the shells from 23 species of pearl producing molluscs, thus covering the majority of the natural and cultured pearls and their host animals found in the market today, in order to better understan...
This article reviews the pearl sector evolution in terms of the production and technology employed.
Since thousands of years, gems were used as tools and amulets often associated with social status and money. At the beginning, gems were used in their rough form, or polished with curved surfaces or engraved. Simple forms of faceting appeared around the start of thirteenth century and it radically improved after the industrial revolution. During di...
The main scope of gem analysis is the identification of a gem, finding out the material of which it is made, whether it is natural or synthetic and if it has been treated/enhanced. The identification depends to some extent on whether the gems are in the rough state, polished, cut, and even on the way in which they are mounted. Sometimes gems mounte...
Gems have been used in the manufacture of jewellery and as ornaments since antiquity.
Nowadays, gemmology, i.e., the study of gem materials, is one of the most rapidly expanding fields in the earth sciences. Recent statistics have shown that about 15 billion Euros are annually at stake. This Special Issue emphasises the recent advances in both fund...
When examining a piece of antique jewellery or object for its authenticity, it is not only important to know about the types of gemstones that existed at the time, but also about the various types of treatments, imitations and synthetic gems. Treatments involve all processes used to modify the appearance of gem materials in order to make the more a...
An answer to most archaeometrical questions can be obtained via the gem analysis presented in the previous chapters. The vast majority of published studies on items of archaeometrical interest are focused on gem identification. Usually the items are mounted, so the possible methods to use are restricted. Additionally, for security reasons most of t...
Gems are materials used for adornment or decoration that must satisfy several criteria where they must be aesthetic and visually appealing; relatively rare; hard and tough enough to resist "normal" wear; and able to withstand corrosion by skin contact and cosmetics [1]. Gems have been used since antiquity thus, gemology, the science dealing with ge...
The present study applied LA–ICP-MS on gem-quality emeralds from the most important
sources (Afghanistan, Brazil, Colombia, Ethiopia, Madagascar, Russia, Zambia and Zimbabwe). It revealed that emeralds from Afghanistan, Brazil, Colombia and Madagascar have a relatively lower lithium content (7Li < 200 ppmw) compared to emeralds from other places (7...
In the Hellenides Orogen, minerals of various gem quality occur in various rock types from mainly four tectono-metamorphic units, the Rhodope, Pelagonian, and the Attico-Cycladic massifs, and the Phyllites-Quartzites unit of Crete Island. In crystalline rocks, gemstones are related to both regional metamorphic-metasomatic processes (e.g., gem corun...
The distribution of chromophores and the composition of the chromium-bearing spinels in Uralian emeralds and alexandrites were studied for the first time. It was proved the main source of chromium for the coloring of emeralds and alexandrites from the Mariinsky deposit was the chromium-bearing spinels of the Bazhenov ophiolite complex. The rare min...
The present study applied Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) on a large number of natural and cultured pearls from saltwater and freshwater environments, which revealed that freshwater (natural and cultured) pearls contain relatively higher quantities of manganese (Mn) and barium (Ba) and lower sodium (Na), magn...
The distribution of chromophores and the composition of chromium-bearing spinels in Uralian emeralds and alexandrites were studied for the first time. It was prooved the main source of chromium for the coloring of emeralds and alexandrates from the Mariinsky deposit was chromium-bearing spinels of the Bazhenov ophiolite complex. The rare mineral zi...
Five sapphires from the secondary placer deposits of Ratnapura and Balangoda in Sri Lanka were classified as being of metamorphic/metasomatic/non-basalt-related origin based on trace-element analysis (LA-ICP-MS) and inclusion characterization. Two sapphires—one from each deposit—contained suitable zircon inclusions that were dated using the LA-ICP-...
Kyshtymites are the unique corundum-blue sapphire-bearing variety of anorthosites of debatable geological origin found in the Ilmenogorsky-Vishnevogorsky complex (IVC) in the South Urals, Russia. Their mineral association includes corundum-sapphire, plagioclase (An61–93), muscovite, clinochlore, and clinozoisite. Zircon, churchite-(Y), monazite-(Ce...
Greece contains several gem corundum deposits set within diverse geological settings, mostly within the Rhodope (Xanthi and Drama areas) and Attico-Cycladic (Naxos and Ikaria islands) tectono-metamorphic units. In the Xanthi area, the sapphire (pink, blue to purple) deposits are stratiform, occurring within marble layers alternating with amphibolit...
Blue sapphire of gem quality was recently discovered in spinel–chlorite–muscovite rock within meta-ultramafites near the Ilmenogorsky alkaline complex in the Ilmen Mountains of the South Urals. More than 20 minerals were found in the assemblage with the blue sapphire. These sapphire-bearing rocks are enriched in LREE and depleted in HREE (with the...
Over the past ten years, gemological laboratories have been replacing film-based microradiography with real-time X-ray microradiography (RTX). This paper compares the output quality and resolution provided by two RTX units fitted with different detectors: an image intensifier (II) and a flat panel detector (FPD) using the same type of X-ray generat...
The obtained data by the studing of inclusion and geochemistry of blue corundum from syenite pegmatites in Ilmen Mountains allow the providing of a closer genetic linckage with those of alluvial and eluvial deposits of blue - green - yellow sapphires (BGY) related to the alkali basaltic fields in Houai Sai (northern Laos) and several mines in Chant...
Sapphires in the Ilmen Mountains of Russia's South Urals are found in syenite pegmatites where the mineral forms blue transparent to translucent megacrysts up to 6 cm in length. The corundum crystallized during the magmatic stage in equilibrium with columbite-(Fe), K-Na-feldspar, and ± perthite. There was a later metasomatic stage in which muscovit...
Raman spectra were obtained on a set of five gems presented as massive variscite, from the three major sources of this gem-quality material. In parallel, micro-FTIR in reflectance and chemical analysis were performed on the same samples, to further characterize them. Surprisingly, four out of five samples are found to be metavariscite, which has be...
Sapphires from Russia’s Ilmen State Reserve may provide insight into gem corundum from secondary placers.
An occurrence of variscite containing strengite, as well as other minerals from both the variscite and metavariscite groups, was discovered in the late 1970s in central Tajikistan. The material, ranging from light blue to light green to green, is suitable for cabochon cutting. The samples presented in this study showed traces of sulfur and arsenic,...
More than 300 natural and synthetic emeralds from various sources were examined with Raman spectroscopy. Of this set, 36 KBr pellets of different samples were also examined with FTIR spectroscopy. In many cases, the presence or absence of specific Raman and FTIR bands, and the exact position of apparent maxima, are correlated to the weight percenta...
Raman spectroscopy was used for the characterization of seven gem quality green ‘jade’ samples and three green ‘jade’ samples of archaeological importance. The results were also compared with those acquired by other nondestructive techniques such as classical gemology, energy-dispersive X-ray fluorescence (EDXRF), ultraviolet-visible-near infrared...
In the last five years, fine Burmese blue sapphires from the Baw Mar area of Mogok have reached the market. The faceted stones typically show a strong pleochroism from greenish to violetish blue when viewed perpendicular and parallel to the c-axis, respectively, with medium to strong saturation and medium to dark tone. Most of the samples were rela...
The methods of luminescence spectroscopy and microscopy are widely used for the analysis of gem materials. This paper gives an overview of the most important applications of the analysis of laser and UV excited luminescence by spectroscopy and visually by microscopy with emphasis on diamond, and specifically natural type Ib diamond, little studied...
Experimental saltwater cultured pearls produced after xenotransplantation between P. margaritifera and P. maxima were studied using UV-Vis-NIR and PL spectroscopy as well as radiography. The results further demonstrate that the graft (saibo) largely determines the coloration and nacre thickness of the cultured pearl.
Варисцит и штренгит - редкие минералы класса фосфатов. Практическое значение имеет варисцит, похожий на бирюзу, который с Неолита использовался в качестве ювелирного украшения: подвесок, кулонов, бус, реже колец. Запасы самого известного месторождения варисцита (юталита) в США практически исчерпаны. Минерал является сравнительно редким. В настоящее...
Analytical Archaeometry describes this interesting and challenging field of research - on the border between natural sciences (chemistry, spectroscopy, biology, geology) and humanities (archaeology, (art-)history, conservation sciences). It fills the gap between these two areas whilst focussing on the analytical aspects of this research field. The...
The gems that adorn two golden chalices from Einsiedeln Abbey (Switzerland) crafted in 1609 and 1629 were investigated using Raman spectroscopy. The results were also compared with those obtained by other non‐destructive means such as microscopy and energy‐dispersive X‐ray fluorescence. The chalice made in 1609 was adorned with 16 corundum (15 rubi...
Natural-color saltwater cultured pearls (SWCPs) from Pinctada maxima were studied using UV-Vis-NIR and PL spectroscopy to better understand the mechanisms of their coloration and to separate them from other SWCPs with similar natural colors. Several spectral features were observed, suggesting that the samples' bodycolor is due to a mixture of pigme...
Raman spectroscopy has become a routine technique in gemmological laboratories since the late 1990s. It is mostly used for identification of inclusions and this is of interest in determining the geographical origin of a gem by means of specific inclusions or mineral associations. Raman spectroscopy also helps to detect treatment, e.g. modification...