Percussion figures in crystals

Summary

The impact of a hard steel sphere on the optically polished surface of a solid results in a permanent deformation of the surface and also produces fractures or rearrangements in the interior of the solid. These have been studied with crystals of quartz, calcite, barytes and felspar and also with a few polycrystalline solids. The results of the study show clearly that the nature of the percussion figure exhibited by a solid is a characteristic property of the material and is related to its inner structure and symmetry. The paper is illustrated by a series of photographs.