Abstract
AN article by G. W. Willard (Bell Lab. Rec., 22, No. 7; March 1944) deals with the methods used in inspecting quartz crystals and in determining the axis orientation. In the original crystallization of quartz, foreign substances, such as other minerals or bubbles of gas or liquid, may be included, and part of the inspection procedure is undertaken to locate such inclusions so that they may be cut away, One of the dangers of using plates with inclusions is that the resulting discontinuities in their elastic and thermal properties may cause them to crack under the influence of temperature changes. Another common defect is the presence of cracks, due either to the effect of inclusions or to the rough treatment the quartz receives in river beds or in being broken from its natural formation. These cracks may be completely internal and very fine, and thus not apparent on casual inspection. Another common defect arises from small interior bubbles. These may be isolated or grouped irregularly, or in very fine form may exist in lines or in plane or curved sheets, when they are called needles, phantom planes, or veils. So common are defects in quartz that only one in a hundred of the mined stones is saved for piezoelectric use.
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Axis Orientation of Quartz Crystals. Nature 154, 157–158 (1944). https://doi.org/10.1038/154157b0
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DOI: https://doi.org/10.1038/154157b0