44 CRYSTALLOGRAPHY. 
that is, planes having the same inclinations to either diametral 
section, The following are examples: 

AXINITE. ANORTHITE. AMBLYGONITE, 
The difference in angle from monoclinic forms is often very 
small. This is true in the Feldspar family. Fig. 2, of the 
feldspar calied anorthite, is very similar in general form to 
fig. 4, of orthoclase, 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 O and 7-2 (te two directions 
