Discriminating hematite and magnetite via Scanning Electron Microscope–Mineral Liberation Analyzer in the −200 mesh size fraction of iron ores

D. C. Grant, D. J. Goudie, C. Voisey, M. Shaffer, P. Sylvester

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

Scanning Electron Microscope–Mineral Liberation Analysis (SEM–MLA) can be used to discriminate between hematite and magnetite in iron ores. However, achieving backscattered electron (BSE) segmentation between the two minerals is difficult for particles ≤75 µm using typical preparation and analysis methods for the MLA method based on a tungsten filament SEM (Quanta 400) with 25 kV high voltage. Preparing iron ore sample mounts using a slow-speed polishing method, and conducting the experiment on a field emission gun SEM–MLA (Quanta 650) with the high voltage setting lowered to 15 kV reduces instrument noise and results in very clean BSE images and segmentation. This method requires new X-ray standards for each mineral at 15 kV because of major changes in the spectra at lower kV. However, once these X-ray spectra are added to the mineral reference list, effective segmentation can be achieved and an accurate analysis obtained.

Original languageEnglish
Pages (from-to)30-37
Number of pages8
JournalApplied Earth Science: Transactions of the Institute of Mining and Metallurgy
Volume127
Issue number1
DOIs
StatePublished - Jan 2 2018

Keywords

  • Iron ore
  • automated mineralogy
  • field emission gun
  • mineral liberation analysis
  • scanning electron microscopy

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