Papers by Michael S. Krzemnicki
Journal of gemmology/The journal of gemmology, 2024
The Journal of Gemmology, 2017
The separation of natural from cultured pearls is mainly based on the interpretation of their int... more The separation of natural from cultured pearls is mainly based on the interpretation of their internal structures, which traditionally have been visualized by X-radiography and more recently by X-ray computed microtomography (micro-CT). In this study, the authors present a new analytical approach using a grating interferometer, which simultaneously generates an X-radiograph, a phase-contrast image and a small-scale scattering or darkfield image. The latter two additional images provided by this technique offer detailed and complementary information, as they are especially sensitive for visualizing tiny material inhomogeneities in pearls such as fissures, organic layers and cavity structures. Using seven selected natural and cultured pearl samples and a strand of non-beaded freshwater cultured pearls, the authors demonstrate that this new analytical approach offers versatile and rapid pearl identification possibilities, especially as it is possible to analyse not only single loose pearls but also entire strands and necklaces. Compared to micro-focus digital radiography and micro-CT, certain limitations in resolution still remain with the described prototype setups, and as such this new methodology should be considered a helpful complementary technique to the classical radiography of pearls.
Gems & Gemology, Dec 1, 2011
In this study, we report on a historic turquoise substitute-fossilized dentine, also known as odo... more In this study, we report on a historic turquoise substitute-fossilized dentine, also known as odontolite, ivory turquoise, bone turquoise, or French turquoise. Much of this material consists of fossilized mastodon ivory from Miocene-age (13-16 million years old) sedimentary rocks of the Gers District between the Aquitaine and Languedoc regions of southwestern France (Reiche et al., 2001). The tusks are hosted by alluvial sediments (molasse alternating with fine sand and clay facies) that accumulated in basins during the erosion of the nearby Pyrenees Mountains (Crouzel, 1957; Antoine et al., 1997). The fossilized dentine consists mainly of fluorapatite, Ca 5 (PO 4) 3 F; since medieval times, local Cistercian monks have used a heating process to turn the material light blue (de La Brosse, 1626; Réaumur, 1715; Fischer, 1819), which they thought to be turquoise. These "stones" were originally set in medieval religious artifacts, but came into fashion in the early to mid-19th century (Brown, 2007),
Case Studies in Nondestructive Testing and Evaluation, Nov 1, 2016
In this study, X-ray phase contrast imaging with a grating interferometer is applied on pearls fo... more In this study, X-ray phase contrast imaging with a grating interferometer is applied on pearls for the first time in order to distinguish natural pearls from cultured pearls. Traditionally, this separation is mainly based on X-ray radiography. In order to visualize the internal structure of pearls we used a custom-made grating interferometer setup and performed measurements on three different pearl products, a natural pearl, a beaded cultured pearl and a beadless cultured pearl. To enhance the visibility of the internal pearl structures, we applied a high-pass filter in order to better conclude on the applicability of this technique to the separation of natural and cultured pearls. The study shows that it is possible to visualize internal pearl structures using distinctly shorter exposure times compared to traditional X-ray radiography and that X-ray phase contrast imaging is a promising complementary method for pearl analysis.
The Journal of Gemmology, 2018
Recent developments have brought due diligence, along with tracking and traceability, to the fore... more Recent developments have brought due diligence, along with tracking and traceability, to the forefront of discussions and requirements in the diamond, coloured stone and pearl industries. This is a result of consumer demands for detailed information on the provenance of gems, banking requirements aiming to reduce risk, industry and company initiatives seeking to bring greater transparency, and growing government legislation on mineral supply chains. To address this trend, certification mechanisms and technologies (such as blockchain) are being developed to solve inherent traceability challenges. As applied to gems, such standards and associated technology could benefit from the support of existing gemmological approaches (e.g. geographical origin determination) to enhance traceability and transparency measures. Recent initiatives are not just limited to corporate social responsibility reporting and due diligence requirements, but they also embrace supply chain management (including quality control and process improvements)-for example, to correctly identify and disclose treated and synthetic materials throughout the jewellery industry-as well as address consumer demand for provenance information. This article provides an overview of current trends and developments in the tracking and traceability of gems, along with an explanation of the terms used in this context. T raceability and transparency-including tracking (from mine to market) and tracing (from market to mine)-of coloured stones, diamonds and pearls is an increasingly important topic in the industry, as shown by recent research and reports (Archuleta, 2016; Walker, 2017; CIBJO, 2018; Human Rights Watch, 2018). The complex and fragmented nature of the global gem industry means that little information is typically available about these supply chains and how specific gem materials are mined, manufactured and sold. Traceability is one way to provide more transparency, and it is argued that by increasing transparency, supply chain issues can be better mapped and understood, ultimately helping to improve the environmental and social impact of a supply chain (Mol, 2015). Consumers are increasingly interested in knowing where and how the materials they consume are extracted and manufactured (Nash et al., 2016; De Angelis et al., 2017; see also Figure 1). Media and non-governmental organisations are placing the gem industry under increased scrutiny regarding the origin and sustainability footprint of various stones (
EGU General Assembly Conference Abstracts, Apr 1, 2018
EGU General Assembly Conference Abstracts, Apr 1, 2018
Physics Procedia, 2017
Gemmology deals with the characterization of coloured stones, diamonds and pearls used in the jew... more Gemmology deals with the characterization of coloured stones, diamonds and pearls used in the jewellery sector. As the investigated objects are in general rather valuable, a large variety of non-destructive testing methods (e.g. X-ray luminescence, X-ray tomography, UV/VIS spectroscopy, etc.) is routinely used for their inspection and characterisation. In a joint project of Paul Scherrer Institut (PSI), Swiss Gemmological Institute (SSEF) and the University Freiburg, potential application fields of neutron imaging methods (i.e. radiography, microtomography and neutron grating interferometry) in the characterisation and testing of pearls and emeralds were investigated and compared to already established X-ray methods. Neutron tomography yields results with comparable image quality but a different contrast, highlighting in the case of pearls the regions containing organic and hence hydrogen containing material. As such regions composed of low-Z material can be very hard to distinguish from voids inside an object using X-ray tomography, neutron tomography provides important additional information on the tested object due to its complementary properties. The complementarity between neutron and X-ray data shows also in the case of emeralds, where fissures filled with organic fillers are highlighted in the neutron data, while staying concealed in the X-ray data. Metallic inclusions in the emeralds on the other hand appear much more pronounced in the X-ray data, then using neutron imaging. The utilization of both methods on the same sample yields hence additional information on the composition of different regions within the object.
The Journal of Gemmology, 2004
Gems & Gemology, May 1, 2019
The gem-bearing reliquary known as the Talisman of Charlemagne is closely associated with the his... more The gem-bearing reliquary known as the Talisman of Charlemagne is closely associated with the history of Europe. Its legend follows such figures as Charlemagne, Napoleon I, Empress Josephine, Hortense de Beauharnais, Napoleon III, and Empress Eugénie. This study provides new historical information collected in France, Germany, and Switzerland about the provenance of this exceptional jewel, which contains a large glass cabochon on the front, a large blue-gray sapphire on the back, and an assortment of colored stones and pearls. The first scientific gemological analysis of this historical piece, carried out on-site at the Palace of Tau Museum in Reims, France, has made it possible to identify the colored stones and offer insight into their possible geographic origins. Based on our data and comparison with similar objects of the Carolingian period, we propose that the blue-gray sapphire is of Ceylonese (Sri Lankan) origin, that the garnets originate from India or Ceylon, and that most of the emeralds are from Egypt except for one from the Habachtal deposit of Austria. The estimated weight of the center sapphire is approximately 190 ct, making it one of the largest known sapphires as of the early seventeenth century
The Journal of Gemmology, 2004
Canadian Mineralogist, Aug 1, 1998
Graeserite, ideally Fe4t3AsOl3(OH), is a new mineral species of the derbylite gloup, which includ... more Graeserite, ideally Fe4t3AsOl3(OH), is a new mineral species of the derbylite gloup, which includes derbylite, tomichite, a"nd hemloite. It is found in needle-shaped crystals, elongate along the c axis. Graeserils i5 6sn6alinig, space gtoup AXm, with the cell paramelers a 7 .184(2), b 14.289(6), c 5.006(2) A, p 105.17(2)",V 495.9(2) At, z=2, D,a.. =!.56 g/cm3. The VHNxgis_52L (Mohs hardness-595). The strongest five lines of the X-ray powder-diffraction pattern [d in An)(hkD] are: 2.681(100)@31), 2.846(80X131), 1.583(50X351), 3.117 (30)(220), nd 2.029(30)(122). Graeserite is black and metallic, with a black streak; it displays a conchoidal fracture. Pleochroism, bireflectance a"nd internal reflections were not observed. The measured values of reflecrance in air are compared with those of other members of the derbylite group. Electron-microprobe analyses gave TiO2 40.
The Journal of Gemmology, 2017
Five non-nacreous 'pearls' that allegedly came from Tridacna gigas (giant clams) were studied for... more 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 identiication of such imitations is in most cases straightforward, and is mainly based on their characteristic layered structure observed in relected light and with transmitted ibre-optic illumination. Our results are compared with recent reports of other such fake pearls that are often wrongly described as being genuine natural pearls.
Journal of Analytical Atomic Spectrometry, 2021
In recent years, multi-element chemical analysis has been applied to a broad range of solid sampl... more In recent years, multi-element chemical analysis has been applied to a broad range of solid samples in mineralogy, geology, environmental science, biology and beyond. In this study, we present a quantification method for the multi-element composition of minerals and a statistical method to investigate chemical similarity among samples. We obtain almost the entire elemental composition simultaneously using laser ablation inductively coupled plasma time-of-flight mass spectrometry (LA-ICP-TOF-MS). A novel concept of "first measure, then determine" which elements are of interest is introduced for multi-element analysis of geological samples. This case study focuses on major, minor and trace element analysis of emerald, a highly relevant mineral in the gemstone trade. In total, 168 samples were analyzed without a priori knowledge of their geographic provenance. They were grouped/ clustered solely based on similarities in multi-element concentrations using non-linear unsupervised dimension reduction algorithm t-distributed stochastic neighbor embedding (t-SNE). A comparison with a PCA plot reveals that the application of t-SNE results in better cluster separation. The clusters in the t-SNE plot coincide with the geographic provenance of these emeralds, probably due to unique elemental fingerprints within the geological setting in each provenance. Based on our results, we consider LA-ICP-TOF-MS multi-element data acquisition in combination with t-SNE data visualization a powerful and promising tool in mineralogy and geology. Not only for provenance studies, but when combined with further sample characteristics (e.g. spectroscopic features, host rock composition, geochronology, inclusions) it may assist in understanding the geological formation and setting of minerals within their host-rock and their deposits.
Journal Of Asian Earth Sciences: X, Jun 1, 2023
The Journal of Gemmology, 2018
This preliminary study focuses on using secondary ion mass spectrometry (SIMS) to measure relativ... more This preliminary study focuses on using secondary ion mass spectrometry (SIMS) to measure relative carbon isotope ratios for natural and synthetic diamonds (i.e. those grown by both chemical vapour deposition [CVD] and high-pressure, high-temperature [HPHT] techniques). The synthetic diamonds (of both CVD and HPHT origin) had significantly lower relative carbon isotope values than the natural diamonds. The lowest value was obtained for the CVD synthetic diamond sample, in agreement with results from other investigators. More research is desirable on the carbon isotope variation of synthetic diamonds.
The Journal of Gemmology, 1996
The Journal of Gemmology, 2003
Quite saturated pink beryl of Madagascar and Afghanistan are described. They display densities be... more Quite saturated pink beryl of Madagascar and Afghanistan are described. They display densities between 2.91 and 3.10 g/cm 3 and RI values up to 1.608 (n e) and 1.615 (n o) which exceed the values reported so far in the literature. Chemical analyses reveal very high caesium concentrations (up to 15.18 wt.% Cs 2 O). The incorporation of Cs in the structural channels of beryl is mainly coupled with a substitution on the tetradhedrally-coordinated beryllium site. Such stones belong to the so-called tetrahedral beryls. UV-Vis-NIR spectra show manganese and water absorption features typical for morganite. XRD data and Raman spectra reveal a distinct increase in cell parameters (mainly c 0) compared to pure beryl, thus underlining the unusual character of the studied material. While the sample from Afghanistan is semitransparent, transparent stones are found among the samples from Madagascar. Inclusions consist mainly of fine tubes parallel to the c-axis, flat fluid-filled inclusions parallel to the basal pinacoid, and tension fractures. Based on chemical composition, spectral data and colour saturation we suggest that the simple term morganite be retained to describe the stones, unless a new term is approved by the IMA to recognize the extraordinary composition and structure of the material.
The Journal of Gemmology, 1996
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Papers by Michael S. Krzemnicki