Mineralpreparats

Mineralpreparats are prepared mineral specimens used for study and teaching in mineralogy and petrography. They consist of mineral grains or rock fragments that have been cut, ground, and mounted to permit microscopic examination.

Two main forms are thin sections (Dünnschnittpräparate) and polished sections (Polierpräparate). Thin sections are usually about 30 micrometers thick and are observed in transmitted light in a polarizing microscope. Polished sections are thicker, have a flat surface prepared for reflected-light microscopy and, if needed, electron microscopy; they are typically mounted on glass slides with an adhesive such as epoxy resin.

Preparation involves selecting a representative fragment, cutting to size, mounting on a slide with an adhesive, and progressively grinding with finer abrasives to the required thickness. For thin sections the material is thinned to about 30 micrometers; for polished sections the surface is ground and polished to a mirror finish. Optional steps include etching, staining, or impregnation to reveal microstructures, porosity, or mineral interfaces.

Applications include optical identification of minerals (using refractive index, pleochroism, and interference colors under crossed polars), texture and microstructure analysis in rocks, and teaching. Prepared slides are used in university laboratories, museums, and industry for mineralogical and geological study, as well as quality control in mining and materials research.

Historically, mineral preparations became standard in the 19th century with advances in microscopic petrography and standardized mounting and polishing techniques, and they remain essential tools in geological education and research.