13a Albite from Lyon Mountain. Orthographic projection show- 

 ing prevailing type of twin according to the albite law. 

 Forms: b (010), c (001), m (no), M (no), / (130), 'Z (130),. 

 x (101), y (201), p (111) and (in) 



13b Clinographic projection of same 



14a Albite from Lyon Mountain. Orthographic projection of" 

 cross penetration twins according to the albite law 



14b Clinographic projection of same 



15a Pyroxene from Lyon Mountain. Orthographic projection 

 showing forms: a (100), b (010), c (001), m (no), e (on) 

 and i (211) 



15b Clinographic projection of same 



16 Development of planes in the prismatic zone of 15b showing 

 shape and distribution of natural etch pits and their relation^ 

 to adjacent edges 



