. The Bell System technical journal . etch-pits are formed ofminute facets which are definitely related to the cr\^stal structure. The formof these pits and the orientation of the facets may be used to determine theorientation of the crystal structure at the etched surface being examined. The general appearance of four types of etch-pits is shown in the photo-micrographs of Fig. These are the pits that are deyeloped on groundsurfaces which are approximately parallel to the well known X-, Y-, and Z-cut surfaces of right hand quartz, by the action of hydrofluoric acid. It is ETCH TECHNIQUE
. The Bell System technical journal . etch-pits are formed ofminute facets which are definitely related to the cr\^stal structure. The formof these pits and the orientation of the facets may be used to determine theorientation of the crystal structure at the etched surface being examined. The general appearance of four types of etch-pits is shown in the photo-micrographs of Fig. These are the pits that are deyeloped on groundsurfaces which are approximately parallel to the well known X-, Y-, and Z-cut surfaces of right hand quartz, by the action of hydrofluoric acid. It is ETCH TECHNIQUE 17 seen that the positive and negative X-surfaces produce different etch-pits,and are thus usable in determining electrical sense. Further, the pits on allsurfaces have directional properties which allow them to be used for deter-mining the approximate directions of the axis which lie in the etched , to be able to determine orientations from etched surfaces of other / LEFT HAND QUARTZ^x/ ^ ■ ^ \ / RIGHT HAND QUARTZES. ONCOMPRESSION BT^ 0- in conoscope : contracting rings(eyepiece rot clockwise) in polariscope-. analyzerrotated counter-clockwise in conoscope-expanding rings(eyepiece rot. clockwise) in polariscope : analyzerrotated clockwise Fig. —The conventions of handedness, axes, natural faces, and angular sense-of-cutof common oscillator plates, together with the electrical and optical rules for determiningthese characteristics in unfaced stones. orientations than those shown above, requires a knowledge of the appear-ance of the etch-pits developed on such surfaces. A rather complete catalog of etch-pits on all possible surfaces of quartzwas prepared by W. L. Bond,^ using an etched sphere of quartz (Figs. , are from Bond). Thirty-sLx different types of etch-pits were obtainedand their angular range of coverage was found (the X-, Y-, and Z- surface ^ Etch Figures of Quartz, Z. Kristallogr. (a) 99, 1938, pp. 488-498. 18 BELL SYSTEM TECHNICAL JOURNAL
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