Mineral Analysis Facility
The Centre's Mineral Analysis Facility includes a range of microscopic and x-ray instruments from leading manufacturers.
Cameca SX 100 Electron Microprobe
The Cameca SX 100 Electron Microprobe is a fully digitised instrument with highly integrated electronics and full automation which can be set up for unattended analysis and evaluation. It has a standard tungsten electron emitter which produces a beam of electrons of tuneable energy focussed onto the surface of the sample, exciting a volume of ca. 1 µm3. The sample can be moved across the beam in the perpendicular plane, to analyse a selected number of sites. There are five wavelength dispersive detectors, each equipped with a choice of diffracting crystals, allowing simultaneous quantitative analyses of up to five different elements at chosen points across the sample, at a special resolution of ca. 1 µm.
The spectrometer can be programmed to run a series of scans for different combinations of elements, giving a comprehensive elemental analysis of the surface. There is also an energy dispersive detector, used to collect fluorescence spectra allowing identification at each point selected of all the elements present with a fluorescence line at lower energy than the electron beam. The spectrometer can also be set up to map the relative concentrations (non-quantitatively) of up to four elements at a time (or five elements with fewer pixels per map) across a raster of 512 x 512 pixels in a selected area.
The instrument is equipped with an optical microscope which can be centred on the focal point of the electron beam in order to identify areas to sample. It has continuous zoom (from 250 µm to 1.7 mm field) for ease of location of points of interest in inhomogeneous samples.
Samples should be flat, for example a thin section, and must be coated with a thin film of carbon before being introduced into the spectrometer. All measurements take place in a vacuum, therefore volatile samples cannot be used.
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CL CITL 8200 mk3
The CITL cold cathode luminescence 8200 mk3 stage is fitted to a Nikon Labophot optical microscope. This technique allows for the imaging of cathodoluminescent emission following electron bombardment of uncoated samples.
Images can be viewed and recorded on the adjacent PC via the Jenoptik ProgRes digital camera and software.
Instrument access is via online booking following laboratory induction and training with the primary contact.
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FEI/Thermofisher Quanta 650 ESEM - QEMSCAN with Bruker Quantax Micro-XRF source
The Quanta 650 ESEM is fitted with a Field Emission Gun (FEG) enabling the acquisition of sub-micron resolution images of samples. The ESEM is fitted with a large chamber and has a 15 x 15 cm stage movement range in X and Y, allowing for the analysis of a range of sample sizes from millimetres to centimetres. It has the capability to operate under traditional high vacuum mode for viewing conductive and coated samples; low vacuum mode for imaging non-conductive, uncoated or vacuum-sensitive samples and ‘ESEM’ or ‘wet’ mode for analysis of uncoated, hydrated samples.
The Quanta 650 is equipped with a high resolution Bruker Quantax energy dispersive spectrometer (EDS) with 30 mm2 active area for rapid elemental analysis and mapping of specimens, along with automated particle searching and analysis and multi-field, multi-element mapping. The Quanta 650 also houses a Bruker Quantax micro-XRF source for the analysis of samples using X-ray excitation rather than electron, achieving detection limits down to 10s of ppm depending on the element of choice. This ESEM also features the FEI QEMSCAN software for rapid, automated mineralogical/phase analysis of thin sections and polished blocks.
Imaging and routine elemental characterisation and mapping is possible on a wide range of samples. Samples for QEMSCAN analysis need to be flat, well-polished thin section or 30 mm diameter polished blocks.
Instrument access is via online booking following laboratory induction with the primary contact.
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Horiba XploRA PLUS Confocal Raman Microscope
The Horiba XploRA PLUS confocal Raman microscope is equipped with 532 nm and 785 nm wavelength lasers for the analysis of vibrational modes of molecules in geological and environmental specimens, with a useable spectral range of 50 to 4000 /cm. The microscope is equipped with an automated stage, autofocus system and fast mapping software for unattended mapping.
Instrument access is via online booking following laboratory induction with the primary contact.
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Gemini 2360 Surface Area Analyser (BET)
The Gemini 2360 Surface Area Analyser measures the surface area of samples by making use of the Brunauer-Emmett-Teller (BET) theory. Granulated or powdered samples are first purged of adsorbed water by heating under a stream of helium for several hours, using a Micromeritics FlowPrep 060. The purged samples are then evacuated and cooled using liquid nitrogen, before nitrogen gas is admitted to the sample vial and an identical empty vial. A differential pressure transducer measures the imbalance in pressure between the sample and blank vials, caused by the adsorption of gas onto the sample surface. The system uses this data to calculate the number of molecules of nitrogen required to form a monolayer on the sample surface and, since the molecular dimension of nitrogen are known, calculates the surface area of the sample in square metres per gram.
Access to the equipment is strictly via pre-arranged access with the primary contact.
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X-ray diffraction laboratory
The X-ray diffraction laboratory deals with classic geological problems such as soil lithography and mineral phase identification, using two diffractometers: a Bruker D2 Phaser and a Bruker D8 Advance, both equipped with auto-sample changers which allows us to run batches of standard powder diffraction samples. A variety of anaerobic and low-background holders allows us to obtain good data for air sensitive samples and low sample volumes.
Both diffractometers have Lynxeye detectors and the D8 is fitted with a Göbel mirror which focuses the X-ray beam, giving us beam intensity comparable to first generation synchrotron. It is this beam intensity that allows us to perform reflectometry experiments, measuring the X-rays reflected from mineral surfaces to deduce surface roughness. We can also collect diffraction patterns from non-powdered samples, for example those too precious to powder, such as meteorites and archaeological samples.
Since the D8 can be operated in theta-theta and theta- 2 theta geometry, we can take further advantage of the precise control over sample height afforded us by the reflectometry stage to perform depth profiling of the surface 1-2 μm of samples, by varying the incident angle of the X-ray beam and hence the X-ray penetration depth.
Our facilities are available for commercial use. Instrument access is via online booking following laboratory induction with the primary contact.