Modern X-ray Diffraction Techniques for Exploration and Analysis of Ore Bodies

X-ray diffraction (XRD) can provide useful information about the composition of an ore sample in terms of quantification of crystalline phases and also amorphous content. XRD is also a powerful technique for studying substitutional solid solutions that can affect mining productivity, such as determining lattice bound aluminum in Goethite. Knowledge of the phases present can predict processing required to beneficiate the ore (flotation, magnetic separation, etc), or further upstream can dictate the best ore bodies to mine. In the analysis of iron ore, XRD can identify the phases containing iron, such as Hematite Fe2O3, Magnetite Fe3O4, and Goethite FeO(OH), and any other mineral phases present, especially silicas. Quantitative analysis is possible by various classical methods such as straight line or polynomial calibration with standards, but modern quantification analysis techniques such as Rietveld analysis or full pattern autoscale analysis are attractive alternatives, as they do not require any standards. These methods offer impressive accuracy and speed of analysis. The Rietveld method compares calculated vs. experimentally derived X-ray powder diffraction patterns for a phase, adjusting a wide-variety of crystallographic-, chemicaland modal-abundance parameters until the two are in agreement. Another analysis technique offering great benefit to ore exploration is cluster analysis. This technique greatly simplifies the analysis of a large amount of data from e.g. drill core samplings, and automatically sorts closely related scans of an experiment into separate clusters and marks the most representative scan of each cluster as well as outlying patterns. This can facilitate multi-dimensional compositional mapping of ore deposits, identifying regions of favorable mineral composition. A case study of the XRD analysis of hexagonal and monoclinic pyrrhotite phases, which are often associated with base and precious metal ore bodies, will be presented, with comparisons to other analytical techniques. Understanding the ratios of these phases is an important component of any study relating the genesis, mineral distribution and subsequent beneficiation of magmatic ores. Details of the techniques used, sample optimization methodologies, results, data precision and limitations will be discussed. The approaches have enormous potential as an inexpensive, reliable tool, useful in the characterization of ore materials from any geological environment.