394: K T. Allen, F. K Wright and J. K. Clement— 



Mg-Pyroxene =1*033 : 1 : 0'77 ±-01 

 Enstatite = 1-0308 : 1 : 0-5885 



Diopside = 1*0934 : 1 : 0-5894 



These relations appear even more clearly in a gnomonic pro- 

 jection of the most prominent forms of the three minerals 

 (fig. 5). The character of the projection of the principal forms 

 of the Mg-pyroxene, although distinctly monoclinic in aspect, 



is closely related to that of the enstatite projection, and only 

 vaguely to that of diopside. It is clear from the figure that 

 the principal zones for diopside do not coincide with those of 

 the Mg-pyroxene, but are located in an intermediate position. 

 Though the symbols of the latter might be expressed very 

 roughly in terms of diopside by choosing for the basal pina- 

 coid of the Mg-pyroxene the possible form (102) in place of the 

 present basal plane, thus complicating the entire set of sym- 

 bols, the differences in distances between corresponding forms 

 are even then too great to justify this change, and cast, there- 



