Mineral Liberation Analysis (MLA)
The Helmholtz Institute Freiberg for Resource Technology has two Scanning Electron Microscopy (SEM) which are connected to two detectors for performing energy dispersive X-ray spectroscopy (EDS). All SEM´s are equipped with the MLA-Suite software from FEI for a rapid, spatially resolved, automatic, petrographic analysis of solid samples.
- Scanning Electron Microscopes: FEI Quanta 650 MLA-FEG
- Detectors: Bruker Quantax X-Flash 5030 EDS-Detectors
- MLA-Suite der Firma FEI
- Efficient tool for different fields of application, e.g. in geoscience, exploration, processing, material science, and chemistry
- Analysing method for a wide range of natural and artificial materials
- Qualitative as well as quantitative analysis
- Fast detection of large surfaces
- Low detection limits (10-3 g/g (B - U)) for the most common mineral phases and materials (very few particles per sample, >1 µm)
- Solid, vacuum-resistant, vaporized with carbon
- Sample types:
- Round micropscope slides 25, 30 or 40 mm
- Thin and thick sections 28 x 48 mm
- Single samples 15 x 15 cm
- No differentiation between minerals with the same chemical composition but a different chrystal structure (e.g., pyrite-markasite)
- The minimum grain size detectable is ~1 µm
- H, He, Li, Be, B are not detectable
- A very rough sample surface can cause problems
- K. Bachmann, P. Menzel, R. Tolosana-Delgado, C. Schmidt, M. Hill, J. Gutzmer
“Multivariate geochemical classification of chromitite seams in the Bushveld Complex, South Africa”, Applied Geochemistry (2019)
- M. Kern, J. Kästner, R. Tolosana-Delgado, T. Jeske, J. Gutzmer
“The inherent link between ore formation and geometallurgy as documented by complex tin mineralization at the Hämmerlein deposit (Erzgebirge, Germany)”, Mineralium Deposita (2019)
- Bachmann, K., Frenzel, M., Krause, J., Gutzmer, J.
“Advanced Identification and Quantification of In-Bearing Minerals by Scanning Electron Microscope-Based Image Analysis”, Microscopy and Microanalysis, (2017)
How does it work?
The MLA software combines information from backscattered electron (BSE) images with the characteristic EDS spectra of the sample material. To create a BSE image, a focused primary electron beam scans across a flat sample surface. The software then separates the particles of interest from the rest of the image. Depending on the measurement conditions, it records one or more EDS spectra for determining the different material phases. An electron beam with an excitation voltage of 15 - 25 keV at a sample current of 10 nA and the highest possible counting rate are used in order to achieve short measuring times (4 - 10 ms) per measuring point. This results in a high sample throughput.
- Fandrich, R., Gu, Y., Burrows, D., Moeller, K. (2007) „Modern SEM-based mineral liberation analysis“. International Journal of Mineral Processing, 84, pp. 310-320.
- Gu, Y. (2003) “Automated Scanning Electron Microscope based Mineral Liberation Analysis”. Journal of Minerals & Materials Characterization & Engineering, 2, pp. 33-41.