Materialographic preparation of geological and mineralogical samples

Materialographic sample preparation is essential for the reliable qualitative and quantitative analysis of geological and mineralogical samples. The aim of this presentation is to present optimized preparation methods for rocks, ores, minerals, fossils and material from tailings piles, which is becoming increasingly important in a world with fewer resources. The methods described include precise separation with different machines and cutting wheels adapted to the sample hardness and structure, whereby gentle sample treatment is necessary, especially in the case of porous, brittle or powdery samples. For tailings pile material, which often has heterogeneous compositions, high porosity and variable grain sizes, special mounting and impregnation techniques are recommended to ensure representative and artifact-free sample preparation.

Mounting is preferably done with low-viscosity epoxy resins under vacuum to completely fill pores and cracks and stabilize powder mixtures. Alternatively, warm-curing or light-curing mounting agents are used. The subsequent grinding and polishing processes are carried out with modern, semi-automatic and fully automatic grinding and polishing machines. Various abrasives and polishing agents, especially diamond and silicon carbide discs, are selected depending on the sample material and preparation target. Thin sections are produced by multi-stage grinding to final thicknesses of 20 to 30 μm, whereby precise control of flatness and thickness is essential.

The techniques presented enable high reproducibility, a significant reduction of preparation artifacts and excellent surface quality. This increases the informative value of light and scanning electron microscopy as well as analytical investigations. Targeted sample preparation is therefore a basic prerequisite for reliable geoscientific analyses, especially with regard to sustainable raw material extraction from secondary sources such as tailings piles.