ETCH TECHNIQUE 



43 



to the labeling of this particular view, only. Thus if a section is entirely 

 right quartz and of the electrical sense shown at A the whole surface of the 

 section will appear bright in view A and dark in all other views. If a section 

 is all right quartz, but partly of the electrical sense shown in A and partly 

 that shown in B, then part of the surface will appear bright in A and the 

 other part will be bright in B (the whole surface will be dark in C and D) 



Fig. 5.23 — The four possible conditions of handedness and electrical sense in a single 

 section are shown here. In each view the handedness and sense is for only the bright 

 portion of that view. The a and b regions are seen to be both of right quartz but of opposite 

 electrical sense, hence electrical twins. (Flaws indicated by/ are to be disregarded). 



A section containing all four possible twins would exhibit bright regions in 

 each view, and a different bright region in each view. All bright regions 

 would fit together to make a complete map of the surface. Only the bright 

 portion of each view has the handedness and electrical sense indicated for 

 that view. 



Figure 5.23 shows a Z-cut section containing twins of the four possible 



