u 



CRYSTALLOGRAPHY. 



that is, planes having the same inclination s to either diametral 

 section. The following are examples : 



AXINITE. 



ASTORTHITE. 



AMBLYGOXITE. 



The difference in angle from monoclinic forms is often very 

 small. This is true in the Feldspar family. - Fig. 2, of the 

 feldspar called anorthite, is very similar in general form to 

 fig. 4, of orthociase, which is monoclinic. This is still more 

 strikingly seen on comparing fig. 4 with fig. 5, representing 

 a crystal of oligoclase, another one of the triclinic feldspars. The 



ORTHOCLASE. 



OLIGOCLASE. 



planes on the two are the same with one exception ; but there 

 is this difference, that in orthoclase, as in all monoclinic crys- 

 tals, the angle between the planes and i-l (the two direction* 



