Combined XRF, XRD, SEM-EDS, and Raman Analyses on Serpentinized Harzburgite (Nickel Laterite Mine, New Caledonia): Implications for Exploration and Geometallurgy

International audienceDifferent techniques have been combined to determine the crystallography and the chemical composition of serpentinized harzburgite sampled in a drill core coming from the lower part of the New Caledonia ophiolite. Specifically, this serpentinized harzburgite is the common bedrock of most of the nickel laterite mines in New Caledonia. Most of the minerals present in serpentinized harzburgite were analyzed by Raman spectroscopy and XRD. In this study, Raman spectroscopy has been applied for the first time to estimate the nickel content in lizardite, forsterite, talc, and goethite. The analyses confirm that the major serpentine minerals show two varieties: (1) Ni-bearing lizardite and (2) Ni-free lizardite. Furthermore, Ni-rich forsterite, enstatite, Ni-rich talc, sepiolite, periclase (MgO), and quartz were detected. Additionally, Raman spectroscopy evidence minor phases not detected by XRD: anatase, rutile, pyrite, hematite, chromite, magnesiochromite, and Ni-rich goethite. Our results show that the Ni substitution is only present in lizardite exhibiting turbostratic-stacking disorder. This finding has potential for being used as an exploration tool using short-wave-infrared spectroscopy online or as a portable instrument, and for defining geometallurgical parameters for processing these complex ores

Challenges in coupled on-line-on-mine-real time mineralogical and chemical analyses on drill cores

The SOLSA project aims to develop an innovative on-line-on-mine-real-time expert system, combining sonic drilling, mineralogical and chemical characterization and data treatment. Ideally, this combination, highly demanded by mining and metallurgical companies, will speed up exploration, mining and processing. In order to evaluate the instrumental parameters for the SOLSA expert system, portable and laboratory analyses have been performed on four samples with contrasting lithologies: siliceous breccia, serpentinized harzburgite, sandstone and granite. More precisely, we evaluated the influence of the surface state of the sample on the signals obtained by portable X-Ray Fluorescence (pXRF) for chemistry and portable Infra-Red spectroscopy (pIR) for mineralogy. In addition, laboratory Raman spectroscopy, X-Ray Diffraction (XRD), XRF and ICP-OES laboratory analyses were performed to compare surface bulk mineralogical and chemical analyses. This presentation highlights (1) the importance of coupling chemical and mineralogical analytical technologies to obtain most complete information on samples, (2) the effect of the sample surface state on the XRF and IR signals from portable instruments. The last point is crucial for combined instrumental on-line sensor design and the calibration of the different instruments, especially in the case of pXRF

3D Imaging on heterogeneous surfaces on laterite drill core materials

The SOLSA project aims to construct an analytical expert system for on-line-on-mine-real-time mineralogical and geochemical analyses on sonic drilled cores. A profilometer is indispensable to obtain reliable and quantitative data from RGB and hyperspectral cameras, and to get 3D definition of close-to-surface objects such as rheology (grain shape, grain size, fractures and vein systems), material hardness and porosities. Optical properties of minerals can be analyzed by focusing on the reflectance. Preliminary analyses were performed with the commercial scan control profilometer MI-CRO-EPSILON equipped with a blue 405 nm laser on a conveyor belt (depth resolution: 10 μm; surface resolution: 30x30 μm2 (maximum resolution; 1m drill core/4 min). Drill core parts and rocks with 4 different surface roughness states: (1) sonic drilled, (2) diamond saw-cut, polished at (3) 6 mm and (4) 0.25 μm were measured (see also abstract Duée et al. this volume). The ΜICRO- EPSILON scanning does not detect such small differences of surface roughness states. Profilometer data can also be used to access rough mineralogical identification of some mineral groups like Fe-Mg silicates, quartz and feldspars). Drill core parts from a siliceous mineralized breccia and laterite with high and deep porosity and fractures were analyzed. The determination of holes’ convexity and fractures) is limited by the surface/depth ratio. Depending on end-user’s needs, parameters such as fracture densities and mineral content should be combined, and depth and surface resolutions should be optimized, to speed up “on-line-on-mine-real- time” mineral and chemical analyses in order to reach the target of about 80 m/day of drilled core

Efficient long-term open-access data archiving in mining industries

Efficient data collection, analysis and preservation are needed to accomplish adequate business decision making. Long-lasting and sustainable business operations, such as mining, add extra requirements to this process: data must be reliably preserved over periods that are longer than that of a typical software life-cycle. These concerns are of special importance for the combined on-line-on-mine-real-time expert system SOLSA (http://www.solsa-mining.eu/) that will produce data not only for immediate industrial utilization, but also for the possible scientific reuse. We thus applied the experience of scientific data publishing to provide efficient, reliable, long term archival data storage. Crystallography, a field covering one of the methods used in the SOLSA expert system, has long traditions of archiving and disseminating crystallographic data. To that end, the Crystallographic Interchange Framework (CIF, [1]) was developed and is maintained by the International Union of Crystallography (IUCr). This framework provides rich means for describing crystal structures and crystallographic experiments in an unambiguous, human- and machine- readable way, in a standard that is independent of the underlying data storage technology. The Crystallography Open Database (COD, [2]) has been successfully using the CIF framework to maintain its open-access crystallographic data collection for over a decade [3,4]. Since the CIF framework is extensible it is possible to use it for other branches of knowledge. The SOLSA system will generate data using different methods of material identification: XRF, XRD, Raman, IR and DRIFT spectroscopy. For XRD, the CIF is usable out-of-the-box, since we can rely on extensive data definition dictionaries (ontologies) developed by the IUCr and the crystallographic community. For spectroscopic techniques such dictionaries, to our best knowledge, do not exist; thus, the SOLSA team is developing CIF dictionaries for spectroscopic techniques to be used in the SOLSA expert system. All dictionaries will be published under liberal license and communities are encourage to join the development, reuse and extend the dictionaries where necessary. These dictionaries will enable access to open data generated by SOLSA by all interested parties. The use of the common CIF framework will ensure smooth data exchange among SOLSA partners and seamless data publication from the SOLSA project

Layered tellurides: stacking faults induce low thermal conductivity in the new In 2 Ge 2 Te 6 and thermoelectric properties of related compounds

International audienceA new ternary layered compound In2Ge2Te6, belonging to the hexatellurogermanate family has been synthesized from the reaction of appropriate amounts of the pure elements at high temperature in sealed silica tubes. In2Ge2Te6 crystallizes in the rhombohedral space-group R[3 with combining macron]:H with lattice parameters a = 7.0863(3) Å and c = 21.206(2) Å and its structure is resolved using single crystal X-ray diffraction. The transport properties (Seebeck coefficient, resistivity and thermal conductivity) of compounds belonging to the family AMTe3 (A = In and Cr; M = Ge and Si) are reported. All compounds are p-type semiconductors. InSiTe3 and Cr2Si2Te6 are too resistive to be good thermoelectric materials, with maximal power factors of 10−6 and 10−5 W m−2 K−2 at 473 K, while In2Ge2Te6 and Cr2Ge2Te6 exhibit maximal values of about 10−4 and 10−3 W m−2 K−2 at 673 K, respectively. All compounds exhibit thermal conductivity below 2 W m−1 K−1, with values dropping to 0.35 W m−1 K−1 at 673 K for In2Ge2Te6. Transmission electron microscopy evidences stacking faults explaining such low thermal conductivities. The best ZT values are observed for Cr2Ge2Te6 with 0.45 at 773 K and In2Ge2Te6 with 0.18 at 673 K. Among these layered structures, a spark plasma sintered Cr2Ge2Te6 sample exhibits some thermal conductivity anisotropy but only weakly due to crystallite orientations

Layered tellurides: stacking faults induce low thermal conductivity in the new In 2 Ge 2 Te 6 and thermoelectric properties of related compounds

International audienceA new ternary layered compound In2Ge2Te6, belonging to the hexatellurogermanate family has been synthesized from the reaction of appropriate amounts of the pure elements at high temperature in sealed silica tubes. In2Ge2Te6 crystallizes in the rhombohedral space-group R[3 with combining macron]:H with lattice parameters a = 7.0863(3) Å and c = 21.206(2) Å and its structure is resolved using single crystal X-ray diffraction. The transport properties (Seebeck coefficient, resistivity and thermal conductivity) of compounds belonging to the family AMTe3 (A = In and Cr; M = Ge and Si) are reported. All compounds are p-type semiconductors. InSiTe3 and Cr2Si2Te6 are too resistive to be good thermoelectric materials, with maximal power factors of 10−6 and 10−5 W m−2 K−2 at 473 K, while In2Ge2Te6 and Cr2Ge2Te6 exhibit maximal values of about 10−4 and 10−3 W m−2 K−2 at 673 K, respectively. All compounds exhibit thermal conductivity below 2 W m−1 K−1, with values dropping to 0.35 W m−1 K−1 at 673 K for In2Ge2Te6. Transmission electron microscopy evidences stacking faults explaining such low thermal conductivities. The best ZT values are observed for Cr2Ge2Te6 with 0.45 at 773 K and In2Ge2Te6 with 0.18 at 673 K. Among these layered structures, a spark plasma sintered Cr2Ge2Te6 sample exhibits some thermal conductivity anisotropy but only weakly due to crystallite orientations

Investigation of structural and mechanical properties of BioCaCO3-LDPE composites

International audienc

Investigation of structural and mechanical properties of BioCaCO3-LDPE composites

International audienceThe three different Mollusk shells, Pecten maximus, Crepidula fornicata andCrassostrea gigas, were studied and compared with synthetic and commercial powders. All samples were analysed by X-ray diffraction, Quantitative phase analysis, and quantitative line broadening (microstructure) analysis using the Combined Analysis method. LDPE-CaCO3 composites were prepared in a twin screw extruder in the composition range of 0–10.8 filler content. Ultimate Mechanical properties of dog-bone type injection molded tensile specimens (ISO-527-2-5A) were measured.Results areshowingthatthe biogenic calcium carbonate is less efficient in improving polyethylene stiffness than the synthetic ones, independently of its crystalline form, to use stearic acid coating allows an improvement of the matrix stiffening. The yield strength is unchanged whatever the kind of filler used, which makes shell spares valid for reuse in polymer industry

Raman investigations and ab initio calculations of natural diamond-lonsdaleite originating from New Caledonia

International audienceHere, we report the first occurrence so far of cubic diamond and lonsdaleite in a siliceous breccia hosted in nickel laterite from the Tiébaghi mine, New Caledonia. Diamond and lonsdaleite polytype occurred as minerals in surficial formed siliceous rocks. The vibrational properties and the calculated elastic properties and electronic band structure of 3C-diamond and lonsdaleite were studied by micro-Raman spectroscopy and ab initio calculation. Our measured Raman spectra demonstrate the coexistence of cubic diamond and lonsdaleite based on the correlation between ab initio calculation and experimental results. We showed that the position of the single Raman vibration mode for cubic diamond corresponds to the first order scattering of F2g symmetry at 1332 cm−1. For lonsdaleite, the ab initio calculations predict three fundamental vibrational modes: 1207 cm−1 (E2g), 1307 cm−1 (A1g), and 1330 cm−1 (E1g). The calculated indirect bandgaps of 3C-diamond and lonsdaleite at room temperature are 5.7 eV and 5.2 eV, respectively. The elastic anisotropy calculations show that lonsdaleite has the greatest shear modulus, bulk modulus and young’s modulus compared to cubic diamond, which indicates a high degree of hardness of this hexagonal structure of diamond

Raman investigations and ab initio calculations of natural diamond-lonsdaleite originating from New Caledonia

International audienceHere, we report the first occurrence so far of cubic diamond and lonsdaleite in a siliceous breccia hosted in nickel laterite from the Tiébaghi mine, New Caledonia. Diamond and lonsdaleite polytype occurred as minerals in surficial formed siliceous rocks. The vibrational properties and the calculated elastic properties and electronic band structure of 3C-diamond and lonsdaleite were studied by micro-Raman spectroscopy and ab initio calculation. Our measured Raman spectra demonstrate the coexistence of cubic diamond and lonsdaleite based on the correlation between ab initio calculation and experimental results. We showed that the position of the single Raman vibration mode for cubic diamond corresponds to the first order scattering of F2g symmetry at 1332 cm−1. For lonsdaleite, the ab initio calculations predict three fundamental vibrational modes: 1207 cm−1 (E2g), 1307 cm−1 (A1g), and 1330 cm−1 (E1g). The calculated indirect bandgaps of 3C-diamond and lonsdaleite at room temperature are 5.7 eV and 5.2 eV, respectively. The elastic anisotropy calculations show that lonsdaleite has the greatest shear modulus, bulk modulus and young’s modulus compared to cubic diamond, which indicates a high degree of hardness of this hexagonal structure of diamond