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BELL SYSTEM TECHNICAL JOURNAL 



pits are obtained only on surfaces within 6° to 8°, from the X-, Y-, and Z- 

 surfaces, respectively). Since the development of good etch pits and their 

 exact appearance is considerably affected by the preparation of the surface 

 for etching (fineness of grind), and by the strength of the acid and the 

 length of etching time, and by the manner of illumination when viewing, the 



v' t 



X-CUT (-+-X up) 



X-CUT (^-X up) 



X 

 i 



4 



^ 



Y- CUT 



Z- CUT 



Fig. 5.5 — Photomicrographs of etch-pits on the etched surfaces of common orientations. 

 As seen the etch-pits are deiinitely related to the structure axes of the quartz. 



figures shown here do not represent the exact appearance of pits obtained by 

 other manners of development. However, such figures are reproducible. 

 The use of etch-pits to determine the orientation of a perfectly general 

 surface is complicated by the fact that some different surface orientations 

 give pits not readily distinguished from each other. However, for the sur- 

 faces most commonly encountered in quartz plate manufacture the etch- 



