Swiss Gemmological Institute SSEF

Basel, Switzerland

Swiss Gemmological Institute SSEF

Basel, Switzerland
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Bucher K.,Institute For Geo Und Umweltnaturwissenschaften | Zhou W.,Institute For Geo Und Umweltnaturwissenschaften | Zhou W.,Swiss Gemmological Institute SSEF | Stober I.,Karlsruhe Institute of Technology
Swiss Journal of Geosciences | Year: 2017

The study presents composition data of 87 surface water samples from high alpine catchments of the Zermatt area (Swiss Alps). The investigated area covers 170 km2. It was found that the surface runoff acquires the dissolved solids mostly by reaction of precipitation water with the minerals of the bedrock. Total dissolved solids (TDS) vary from 6 to 268 mg L−1. All collected water shows a clear chemical signature of the bedrock mineralogy. The contribution of atmospheric input is restricted to small amounts of ammonium nitrate and sodium chloride. NH4 is a transient component and has not been detected in the runoff. Evaporation is not a significant mechanism for TDS increase in the Zermatt area. The chemical composition of the three main types of water can be related to the mineralogy of the dominant bedrock in the catchments. Specifically, Ca-HCO3 (CC) waters develop from metamorphic mafic rocks and from carbonate-bearing schists. Mg-HCO3 water originates from serpentinites and peridotites. Ca-SO4 (CS) waters derive from continental basement rocks such as pyrite-rich granite and gneiss containing oligoclase or andesine. The collected data suggest that, together with reaction time, modal sulfide primarily controls and limits TDS of the waters by providing sulfuric acid for calcite (CC waters) and silicate (CS waters) dissolution. If calcite is present in the bedrock, its dissolution neutralizes the acid produced by sulphide weathering and buffers pH to near neutral to weakly alkaline conditions. If calcite is absent, the process produces low-pH waters in gneiss and granite catchments. The type of bedrock and its mineral assemblage can be recognized in water leaving very small catchments of some km2 area. The large variety of water with a characteristic chemical signature is an impressive consequence of the richly diverse geology and the different rock inventory of the local catchments in the Zermatt area. © 2017 Swiss Geological Society

Balmer W.A.,Chulalongkorn University | Balmer W.A.,Swiss Gemmological Institute SSEF | Hauzenberger C.A.,University of Graz | Fritz H.,University of Graz | And 2 more authors.
Journal of African Earth Sciences | Year: 2017

The ruby deposits of the Uluguru and Mahenge Mts, Morogoro Region, are related to marbles which represent the cover sequence of the Eastern Granulites in Tanzania. In both localities the cover sequences define a tectonic unit which is present as a nappe structure thrusted onto the gneissic basement in a north-western direction. Based on structural geological observations the ruby deposits are bound to mica-rich boudins in fold hinges where fluids interacted with the marble-host rock in zones of higher permeability. Petrographic observations revealed that the Uluguru Mts deposits occur within calcite-dominated marbles whereas deposits in the Mahenge Mts are found in dolomite-dominated marbles. The mineral assemblage describing the marble-hosted ruby deposit in the Uluguru Mts is characterised by corundum-dolomite-phlogopite ± spinel, calcite, pargasite, scapolite, plagioclase, margarite, chlorite, tourmaline whereas the assemblage corundum-calcite-plagioclase-phlogopite ± dolomite, pargasite, sapphirine, titanite, tourmaline is present in samples from the Mahenge Mts. Although slightly different in mineral assemblage it was possible to draw a similar ruby formation history for both localities. Two ruby forming events were distinguished by textural differences, which could also be modeled by thermodynamic T–XCO2 calculations using non-ideal mixing models of essential minerals. A first formation of ruby appears to have taken place during the prograde path (M1) either by the breakdown of diaspore which was present in the original sedimentary precursor rock or by the breakdown of margarite to corundum and plagioclase. The conditions for M1 metamorphism was estimated at ∼750 °C at 10 kbar, which represents granulite facies conditions. A change in fluid composition towards a CO2 dominated fluid triggered a second ruby generation to form. Subsequently, the examined units underwent a late greenschist facies overprint. In the framework of the East African Orogen we assume that the prograde ruby formation occurred at the commonly observed metamorphic event around 620 Ma. At the peak or during beginning of retrogression the fluid composition changed triggering a second ruby generation. The late stage greenschist facies overprint could have occurred at the waning stage of this metamorphic episode which is in the range of ∼580 Ma. © 2017 Elsevier Ltd

Cartier L.E.,University of Basel | Cartier L.E.,University of Vermont | Krzemnicki M.S.,Swiss Gemmological Institute SSEF
Gems and Gemology | Year: 2012

The current production of cultured pearls from the black-lipped pearl oyster (Pinctada margaritifera) in the Federated States of Micronesia (FSM) includes mostly beaded as well as blister and nonbead-cultured pearls in a wide array of colors. Pearl farming is carried out on four islands, with plans for commercial production in the near future. The sector is envisaged as a model for economic development and marine conservation. To successfully compete in the marketplace, pearl farmers in the FSM should focus on producing high-quality cultured pearls and explore market differentiation strategies such as the "Micronesian Blue" product. Gemologically, the FSM cultured pearls are indistinguishable from those of French Polynesia that are produced using the same mollusk species. © 2012 Gemological Institute of America.

Krzemnicki M.S.,Swiss Gemmological Institute SSEF | Cartier L.E.,Swiss Gemmological Institute SSEF
Journal of Gemmology | Year: 2017

Five non-nacreous 'pearls' that allegedly came from Tridacna gigas (giant clams) were studied for this report. Our observations revealed that none of them were pearls, but instead they had been manufactured from Tridacna clam shell. The identification of such imitations is in most cases straightforward, and is mainly based on their characteristic layered structure observed in reflected light and with transmitted fibre-optic illumination. Our results are compared with recent reports of other such fake pearls that are often wrongly described as being genuine natural pearls.

Krzemnicki M.S.,Swiss Gemmological Institute SSEF | Hajdas I.,ETH Zurich
Radiocarbon | Year: 2013

For this radiocarbon study, 7 saltwater pearls and 3 shells from pearl oysters have been analyzed. The declared ages of the samples range from the mid-19th century to very recent formations. The analyzed data show the potential of the bomb peak time marker to provide additional information when testing pearls. The analyzed pearls could be distinctly separated in pearls of pre- and post-bomb peak ages, in agreement with the distinction based on the declared ages. The analyzed data further reveals the potential of this method to provide supporting evidence for the historic provenience of a pearl or as an indication of a natural or cultured formation of a pearl. © 2013 by the Arizona Board of Regents on behalf of the University of Arizona.

Meyer J.B.,ETH Zurich | Meyer J.B.,Swiss Gemmological Institute SSEF | Cartier L.E.,Swiss Gemmological Institute SSEF | Cartier L.E.,University of Basel | And 4 more authors.
PLoS ONE | Year: 2013

We report the first successful extraction of oyster DNA from a pearl and use it to identify the source oyster species for the three major pearl-producing oyster species Pinctada margaritifera, P. maxima and P. radiata. Both mitochondrial and nuclear gene fragments could be PCR-amplified and sequenced. A polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay in the internal transcribed spacer (ITS) region was developed and used to identify 18 pearls of unknown origin. A micro-drilling technique was developed to obtain small amounts of DNA while maintaining the commercial value of the pearls. This DNA fingerprinting method could be used to document the source of historic pearls and will provide more transparency for traders and consumers within the pearl industry. © 2013 Meyer et al.

Krzemnicki M.S.,Swiss Gemmological Institute SSEF | Herzog F.,Swiss Gemmological Institute SSEF | Zhou W.,Swiss Gemmological Institute SSEF
Gems and Gemology | Year: 2011

A set of six antique brooches, set with diamonds and light blue cabochons, was investigated with microscopy, Raman analysis, and EDXRF spectroscopy. Most of the cabochons proved to be fossilized dentine, also known as odontolite (mineralogically, fluorapatite). The brooches also contained turquoise and artificial glass. © 2011 Gemological Institute of America.

Schmetzer K.,Taubenweg 16 | Krzemnicki M.S.,Swiss Gemmological Institute SSEF
Journal of Gemmology | Year: 2015

Multiphase inclusions developed in the form of nail-head spicules in a colourless chrysoberyl crystal from Myanmar were examined by optical means and by Raman microspectroscopy. The growth tubes of the multiphase inclusions contain CO2, and the grains attached to the ends of these tubes are most likely chrysoberyl crystals (based on Raman spectra and observation of birefringence), some of which are partially covered with an iron-bearing substance, and possibly also negative crystals. © 2015 The Gemmological Association of Great Britain.

Herzog F.A.,Swiss Gemmological Institute SSEF | Herzog F.A.,GRS Society for plants and Reactor Safety
Journal of Gemmology | Year: 2015

Energy-dispersive X-ray fluorescence (EDXRF) spectroscopy is an important and well-established technique for the non-destructive chemical analysis of gem materials. The suitability of a portable EDXRF instrument for gemmological use was examined with a Niton XL3t GOLDD+ Analyzer manufactured by Thermo Scientific. Analysis of a variety of gem samples (natural, treated and synthetic) yielded qualitative data in the element range from Na to U that were comparable with results obtained from typical benchtop EDXRF instruments. The spectra measured by the portable unit showed well-resolved peaks, and gemmologically important intensity ratios of various elements were easily obtained. Using different collimators and measuring times, loose as well as mounted gems could be measured qualitatively. Although quantitative chemical data were not obtainable in this study, such results should be feasible using a calibration procedure that is optimized for gem analysis. This portable instrument, in conjunction with the use of an He purge unit for a better signal-to-noise (S/N) ratio when analysing light elements, is deemed very useful for smaller laboratories, as well as for larger laboratories offering off-site testing. © 2015 The Gemmological Association of Great Britain.

Swiss Gemmological Institute Ssef | Date: 2015-02-25

The present invention relates to a method for the separation of colourless untreated natural diamonds from:a) colourless diamond imitations;b) colourless treated natural diamonds;c) colourless untreated synthetic diamonds andd) colourless treated synthetic diamonds;comprising:a step A of removing the colourless diamond imitations; anda step B of removing the colourless diamonds which are suspected to be treated natural diamonds, untreated synthetic diamonds or treated synthetic diamonds;wherein said step A is carried out (13) before said step B and using Raman Shift Detection (RSD), the diamonds having, at a predetermined wavelength (W_(e)), an emission signal, the intensity of which is lower than a predetermined value (V_(e)) being removed (11), and wherein said step B is carried out (14) using a UVc transmission measurement (UTM), the diamonds having, in a predetermined wavelength region (R_(a)), a transmission value V_(T) which is higher than a predetermined value (V_(T)), being removed (20). The invention also relates to an apparatus for carrying out this method.

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