X-ray studies of single crystals of quartz and topaz show that there exist on the surfaces of these crystals disturbed layers which are not removed by etching, and that they exert an effect on etched surfaces to a depth of 5 or more microns. The disturbance is not caused by plastic flow. Good, single crystal quartz wafers, 35 microns thick, change when they are etched to 15 microns. The thin plates no longer appear to be single crystal. This "polycrystalline" state is stable at room temperature. Thin crystals undergo further changes when flexed, resulting in a two to threefold broadening of the $\mathrm{Cu} K\alpha$ rocking curves. Similar results were observed with topaz. It is shown that this effect is different from, and may not be related to, the well-known broadening of the Bragg reflections that result from grinding crystal surfaces. As an explanation for the observed phenomena, it is suggested that at least part of the surface energy is in the form of structure irregularity and there results a very thin, glass-like layer that is unstable because it is effectively at a higher temperature than the rest of the crystal. Consequently, recrystallization to a more stable form occurs.

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