How petrographic thin sections are prepared
Whether you are seeking to classify clay minerals, identify problem areas in a quarry or structure, assess mineral potential in a specific geological environment, or identify an archaeological artifact’s geographical source, petrography can provide the answers needed.
Although petrography has numerous applications, it’s most commonly used for identification of rock and ore minerals. One of the methods used in petrography to examine, assess, and identify minerals and aggregates is thin section preparation. This method is also used to assess the microstructural characteristics of a material, such as the concrete used to build a bridge, and whether or not the material will hold up if repaired or replaced.
What Is a Thin Section?
A thin section is a sample of a rock, mineral, concrete, soil, metal, or other material, usually ground and polished down to 30-µm (micron or micrometer) thick sections, so that they can be analyzed under a petrographic, scanning electron microscope, or an electron microprobe.
First, a visual inspection is performed, then a sample is prepared, and if needed, any water present in the material is extracted through low temperature/time, or replacing the water with alcohol. Then, the material must be hardened. Usually a resin used to fix soil samples, is added, then allowed to harden.
Cutting, Polishing, and Mounting
A diamond blade saw is used to cut the prepared sample and create a flat surface. It is then polished to ensure there are no scratches or traces of the cutting process left behind on the sample. The surface should be smooth. Once this smoothness is achieved, the flat surface is attached to a glass slide used for microscopic examination. It is important to use a colorless agent with equal physical properties to cement the smooth edge onto the slide for accurate analysis. Once the sample is mounted, it is cut again, leaving only a very thin slice of the mounted sample attached to the slide. The sample is then polished down further to a thickness of about 30 µm or microns.
Petrographic Service Providers
A thin section preparation service provider should offer a multidisciplinary team, with lab technicians experienced in preparing 
petrographic thin sections with a variety of materials. For more information about our services, or to request a quote, please visit our website and fill out one of our convenient online forms.
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