DIRK WIERSMA / SCIENCE PHOTO LIBRARY DIRK WIERSMA / SCIENCE PHOTO LIBRARY
Deformation structure in schist. Polarised light micrograph of quartz (multicoloured) surrounding a ball of pyrite (brown) in schistose rock (grey). The quartz was formed by intense pressure that acted on the schist. The pressure was a shear force, which caused the pyrite sphere to roll through the schist, changing it into quartz.
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