Gubelin Gem Laboratory

Gem, Hong Kong

Gubelin Gem Laboratory

Gem, Hong Kong
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Huong L.,Vietnam National University, Hanoi | Hager T.,Johannes Gutenberg University Mainz | Hofmeister W.,Johannes Gutenberg University Mainz | Hauzenberger C.,University of Graz | And 5 more authors.
Gems and Gemology | Year: 2012

This article describes the major gem materials of Vietnam, together with their new finds and recent production. The gemological properties and chemical composition of ruby, sapphire, spinel, tourmaline, garnet, and peridot from the most important Vietnamese sources are updated. Other gems such as aquamarine, green orthoclase, topaz, zircon, quartz, and pearls are briefly discussed. Commercially significant deposits of ruby, blue and fancy sapphire, and spinel are located in two northern provinces: Yen Bai (Luc Yen and Yen Binh Districts) and Nghe An (Quy Chau and Quy Hop Districts). Large volumes of blue, green, and yellow sapphire come from the Central Highlands provinces of Dak Lak and Lam Dong, as well as the southern provinces of Dong Nai and Binh Thuan. Of secondary commercial importance are the tourmaline and garnet from Yen Bai and the peridot and zircon from the Central Highlands. © 2012 Gemological Institute of America.

Krzemnicki M.,SSEF Swiss Gemmological Institute | Friess S.,Gloor Instruments AG | Chalus P.,Hoffmann-La Roche | Hanni H.,SSEF Swiss Gemmological Institute | Karampelas S.,Gubelin Gem Laboratory
Gems and Gemology | Year: 2010

The distinction of natural from cultured pearls traditionally has been based on X-radiography. X-ray computed microtomography (μ-CT) has recently been applied to gain more insight into pearl structures. Using this technique, this article presents features observed in a selection of natural pearls and beaded and non-beaded cultured pearls. Based on these observations, μ-CT is shown to be a powerful tool for pearl identification. © 2010 Gemological Institute of America.

Karampelas S.,Gubelin Gem Laboratory | Fritsch E.,University of Nantes | Gauthier J.-P.,University of Lyon | Hainschwang T.,GGTL GemlabGemtechlab Laboratory
Gems and Gemology | Year: 2011

Natural-color saltwater cultured pearls from Pinctada margaritifera were studied by diffuse reflectance UV-Vis-NIR spectroscopy to identify the absorption features associated with their various colors. Nine patterns observed in the visible range demonstrated that individual colors are caused not by one pigment but by a mixture of pigments. © 2011 Gemological Institute of America.

Coccato A.,Ghent University | Karampelas S.,Gubelin Gem Laboratory | Worle M.,Collection Center | Van Willigend S.,Swiss National Museum | Petrequin P.,University of Franche Comte
Journal of Raman Spectroscopy | Year: 2014

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 (UV-Vis-NIR) in absorption, Fourier transform infrared spectroscopy (FTIR) in absorption and micro-FTIR in reflectance. Five samples of gem quality and two samples of archaeological interest were found to be 'jadeite jade', whereas two samples of gem quality and one sample of archaeological interest were 'omphacite jade'. Raman spectroscopy is found to be the most efficient method for their characterization. The results were confirmed with EDXRF and micro-FTIR in reflectance. Data acquired using classical gemology, UV-Vis-NIR absorption and FTIR absorption spectroscopy were similar on 'omphacite jade' and 'jadeite jade'. Copyright © 2014 John Wiley & Sons, Ltd.

Karampelas S.,Gubelin Gem Laboratory | Worle M.,Swiss National Museum | Hunger K.,Swiss National Museum | Lanz H.,Swiss National Museum | And 2 more authors.
Gems and Gemology | Year: 2010

The gemstones that adorn a late-16th-century ciborium from Einsiedeln Abbey in Einsiedeln, Switzerland, were investigated by nondestructive gemological methods and EDXRF and Raman spectroscopy at the Collections Center of the Swiss National Museum. The ciborium is decorated with 17 colored stones: 10 almandine garnets, four grossular garnets, and three sapphires. Inclusions in the sapphires and a historic description of the piece suggest a Sri Lankan origin for the gems. © 2010 Gemological Institute of America.

Karampelas S.,Gubelin Gem Laboratory | Worle M.,Laboratory for Conservation Research | Hunger K.,Laboratory for Conservation Research | Lanz H.,Collections and Documentation
Journal of Raman Spectroscopy | Year: 2012

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 rubies and 1 sapphire), four garnets (two almandine and two grossular), seven quartzes (six amethysts and one citrine) and one peridot (forsterite olivine). All pearls of this chalice were found to be from a saltwater mollusc. The chalice crafted in 1629 was adorned with 23 diamonds. Compilation of all the results does not exclude that the stones mounted to the chalices are of 'oriental' origin. However, more research needs to be done by additional spectroscopic means to shed more light on their origin. Copyright © 2012 John Wiley & Sons, Ltd.

Karampelas S.,Gubelin Gem Laboratory | Lombard A.,Cendanda Indopearls Atlas South Sea Pearls
Gems and Gemology | Year: 2013

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. © 2013 Gemological Institute of America.

Kan-Nyunt H.-P.,Gubelin Gem Laboratory | Karampelas S.,Gubelin Gem Laboratory | Link K.,Gubelin Gem Laboratory | Thu K.,Macle Gem Laboratory | And 2 more authors.
Gems and Gemology | Year: 2013

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 relatively clean under the microscope, showing multiple twinning with whitish needle-like inclusions (presumably boehmite) at the intersections. Often, these inclusions were associated with stress tension fissures. Needles, most likely rutile, were found only occasionally, but small platelets and needle-like particles, probably ilmenite, appeared more frequently. Most of the stones contained surface-reaching open and healed fissures, but crystal inclusions of K-feldspar and mica (identified by Raman) were occasionally encountered. The sapphires also had a relatively high iron content, low gallium, and very low titanium. Their Ga/Mg ratio varied from 0.6 to 17. Their UV-Vis- NIR spectra displayed intense iron-related absorptions, and the FTIR absorption spectra presented mainly boehmite- and mica-related bands. Based on careful microscopic observations, combined with spectroscopic and chemical analysis, the sapphire from Baw Mar can, in most cases, be distinguished from the blue sapphire of other localities. © 2013 Gemological Institute of America.

Kiefert L.,Gubelin Gem Laboratory | Karampelas S.,Gubelin Gem Laboratory
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2011

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 treatment of diamonds, analysis of the nature of a gemstone, analysis of gemstone inclusions and treatments, and the characterisation of natural or colour enhanced pearls and corals. Future developments in gemstone research lie in the closer analysis of the features of Raman and PL spectra and in the combination of several instruments. © 2011 Elsevier B.V. All rights reserved.

Link K.,Gubelin Gem Laboratory
Journal of Gemmology | Year: 2015

The age determination of zircon inclusions in faceted sapphires by LA-ICPMS may provide a valuable tool to support geographical origin determination. In this initial study, U-Pb dating of a zircon inclusion in a pink sapphire from Madagascar yielded an age of 650 million years (Ma), suggesting a syngenetic origin (i.e. formed at the same time as the host sapphire) of the zircon. In a greenish blue sapphire from Madagascar, an included zircon yielded a U-Pb age of 1,750 Ma, pre-dating the host sapphire, and therefore indicating the zircon is an inherited inclusion (i.e. it originated from rocks that existed before the host sapphire crystallized). These results are supported by indications provided from conventional methods of geographical origin determination. This article also discusses the potential influence on U-Pb age dating of post-formation metamorphic events, laboratory heat treatment and the possibility of complex zoning in the zircon inclusions. © 2015 The Gemmological Association of Great Britain.

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