Two rocks--a sandstone and a monominerallic aggregate of calcite crystals--have been deformed by means of detonators exploded on the end faces of cylindrical specimens, and shock levels up to 7 kilobars recorded. Microscopic examination of the deformed cylinders revealed the nature of the deformation and the extent to which it had progressed along the specimen. The sensitivity of quartz to imposed stresses was used to trace the final geometrical distribution of stress in the system which was then related to the theoretical stress distribution having particular regard to the tensions induced by lateral reflections. Both rocks are shown to have accommodated the imposed stresses by separation along grain boundaries and by intergranular and intragranular tensile fractures. It was observed that calcite grains satisfying a minimum size condition dictated by a particular shock level were bent when swept by a spherical shock front.

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