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X-ray Diffraction

X-ray diffraction

X-ray diffraction (XRD) is a rapid analytical technique used for the quantitative determination of the minerals present in crystalline material such as rocks, soils and synthetics. The method depends upon the unique structural properties of crystals of those minerals, whose response to the x-ray beam is determined by the organisation and dimensions of their regular atomic structure.

  • Rapid, reliable and cost effective
  • Over 200,000 entries in the mineral database
  • Identification of the minerals based on their structure and not on their chemistry
  • Calibrated over more than  250 standards minerals
  • Use of the Rietveld method for accurate mineral quantification

Bulk sample quantitative phase analysis is performed, when possible, with the Rietveld method using one of the software packages we have available (e.g. AutoQuan, Siroquant and HighScore Plus). When this is not possible, for example due to a lack of published mineral structure models, we will perform quantification using our in-house normalized Reference Intensity Ratio method (RIR). This is a RIR method that has been calibrated for the instruments present at X-ray Mineral Services by measuring more than 250 reference minerals and mixtures. Qualitative analysis is backed-up by use of internationally-recognised reference libraries of XRD patterns which continue to be improved and augmented.

X-ray Mineral Services are experts in the analysis of clay minerals. Although they might be evident in the bulk sample diffractograms, the most satisfactory method for their identification and quantification is to extract and analyse the <2 micron clay fraction separately. The clay fraction is subjected to 4 different thermo-chemical treatments that allow the unambiguous phase identification of small quantities of clay minerals, including mixed-layer clays.

While the XRD powder method is in widespread application as the best for quantitative analysis of natural mineral samples, there is significant variation in the preparation techniques of laboratories, the variety of instrumentation they operate or the employment of different interpretation software. These variations can affect the outcome and the only way to confirm the accuracy and precision of the method when applied to natural samples is to check against synthetic mixtures of appropriate mineral standards.

X-ray Mineral Services participates in Quantitative Phase Analysis (QPA) international round-robin proficiency tests, including the Reynolds Cup competition and we routinely prepare our own standard mixtures to validate our sample preparation and QPA methods.

– The Reynolds Cup competition

CASE STUDIES