There are several methods that can be used to identify a material, but one of the most common is that of X-ray diffraction (XRD). In this method, a small amount of the powdered material is placed on a glass slide, and exposed to a beam of X-rays. The resulting reflections and reinforcements of the X-rays at characteristic angles are then used to identify the unknown substance.
This method is especially useful for the characterisation of clay minerals, as various treatments (glycol, heat) change the XRD pattern and these changes can provide further information on the nature of the clay phase.
We use 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.
Quantitative analysis of mixtures to determine the exact proportions of different phases can be carried out using Rietveld analysis.