X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy

Due to the regular atomic structure of crystalline material (the crystal lattice) each mineral has its typical X-ray diffraction (XRD) pattern which follows the Bragg equation:

nλ = 2d*sinθ

Consequently, X-ray diffraction can be used to decipher the composition of rocks and is in particular useful for very fine grained rocks rich in clay minerals. This is true, in particular, because clay minerals as phyllosilicates have very strong and easily identifiable XRD patterns. XRD is a semi quantitative method. It uses the height of the individual 2θ peaks in relation to each other to determine the rough amount of the individual minerals present in the sample.

The FTIR spectroscopy is a physical process which is based on the interactions of infrared radiation (electromagnetic radiation with wavelengths of approx. 0.7-500 µm) with matter. In the identification of unknown substances, infrared spectroscopy represents a quantitative method of frequent application. As certain functional groups such as the SiO44-, CO32- or OH group have specific absorption ranges of which the wave numbers are largely independent of the remainder of the molecule, an unknown specimen can often also be identified already on the basis of the absorption frequencies of such groups.

By the combination of XRD and FTIR it is possible to record the modal (true) composition of the geological materials with adequate accuracy and also to correlate them with the chemical composition.

A further method for deciphering qualitatively, but fast and cheap, the phyllosilicates within a specimen is DCM (Dielectric Constant Measurement).



In September 2019 the Swiss National Cooperative for the Disposal of Radioactive Waste (NAGRA) commisioned Gesteinslabor with UCS, Brazilian and triaxial tests on neighbouring rocks of the Opalinus Clay - the rock which will host Switzerland's future facilities for nuclear waste disposal.

Gesteinslabor receives funding from BMWi for the development of a new test rig. With this funding, our company will open up a new business field in renewable energies by implementing an innovative technology to determine the capillary threshold pressure with hydrogen on cap rock of underground gas storage facilities.