Quantitative and structural analysis of clay minerals
Qmineral is specialized in the quantification and structural analysis of individual and interstratified clay mineral types. Our accuracy is the best available on the commercial market as document by our results in the Reynolds Cup competition.
Clay minerals are best studied in the finest size fractions with X-ray diffraction. To ensure a complete extraction of the clay material, Qmineral uses a thorough preparation to remove cementing agents. Oriented slides of the clay-enriched fractions are then measured by X-ray diffraction.
The subsequent quantification of the clay fraction is done by modelling of the X-ray diffraction patterns. Not only the quantitative proportion of each clay type is provided, but also important structural information on the individual clay minerals can be extracted. Accurate densities can be calculated from these mineralogical data. This structural information involves for example:
- Amount of swelling layers in interstratified minerals
- Structural Fe-content in the lattice
- Average crystallite thickness e.g. "Illite crystallinity" or "Kaolinite crystallinity index"
- Degree of interstratification
Figure. Example of clay mineral quantities derived from the XRD analysis of the <2µm fraction of 11 shale deposit samples.
Case study
Importance of sample preparation
Below, the diffraction patterns of oriented slides of 2 different samples are plotted. The left image shows the diffraction patterns of the samples with a standard pretreatment. The right image shows the diffraction patterns of the same 2 samples but with Qmineral's standardized preparation. It is obvious that there is a huge difference in data interpretation. From the left image, it seems the two investigated samples have a completely different clay mineral composition. The procedure of Qmineral however proves that the clay mineralogy of both samples is nearly identical.
Figure. Diffraction patterns of oriented slides of two different samples. (Left) Little sample preparation. (Right) Qmineral sample preparation.