H. A. Miers — Quartz from North Carolina. 421 



apex is truncated by a smooth face which is certainly as per- 

 fect an example of the basal plane upon quartz as any which 

 exist. The face is dull and slightly rounded, and the central 

 portion is slightly raised above the edges as indicated in the 

 figure, but it is sufficiently smooth to yield an image on the 





reflecting goniometer. Measurement in the zone R : — _R = 

 [100:122] gave a series of images occupying an angular 



breadth of about 3-J° 



OR = 49° 24' to 52° 51' mean 51° 7|' 

 OR 50 44 to 54 11 

 — R 103 34f 

 OR 51 47 calculated. 



This face has all the appearance of a corrosion surface and 1 

 share the opinion of Molengraaf that most of the rare planes 

 upon the j^orth Carolina quartz have been produced in this 

 way. 



The crystal is further remarkable for one of the very rare 

 planes which replace the edges of the primary rhombohedron ; 

 only one such edge is developed in the present instance and it 

 is replaced by a face m which is rounded in the zone RR. 



This surface yields a series of somewhat indistinct images 

 in the zone RR which correspond to the following inclina- 

 tions to (100), 



