Several methods can be used to identify a material, one of the most common being X-ray diffraction (XRD). With this method, a small amount of the crushed powdered material is smeared on to a glass slide, and exposed to a beam of X-rays in a non-destructive method. The resulting reflections and reinforcements of the X-rays at characteristic angles are then used to identify crystalline minerals in the unknown substance. Atomic structure of crystalline minerals within a sample are unique to each mineral and therefore interact uniquely with the X-rays producing diagnostic peaks at different diffraction angles (2ϴ).
A number of new clay separation methods have been developed including chemical separation using Sodium pyrophosphate as well as more traditional treatments (glycol, heat). These methods change the XRD patterns, and the new spectra after clay separation can provide further information on the nature of the clay phase.
Analysis in this laboratory is primarily carried out on rock, ore mineral, sediment and soil powders using a Philips PW1830/3020 spectrometer and Copper Kα X-rays. Mineral peaks can be identified manually or automatically from the ICDD Powder Diffraction File (PDF) database, using specialised software Match! v3.11.2. (https://www.crystalimpact.com/match/)
Quantitative analysis of mixtures to determine the exact proportions of different phases can be carried out using Rietveld analysis which is also run from within the Match! software.