L6 



NEW YORK STATE MUSEUM 



Some of the combinations of forms in this group are given in 

 fig. 38-43, the lettering of the faces being the same as that used 

 for the corresponding simple forms. 



Fig. 41 Fig. 42 Fig. 43 



Pyritohedral group 

 The general symmetry of the pyritohedral group is shown in 

 fig. 44. The crystallographic axes are axes of binary symmetry 



Fig. 44 



Fig. 45 



and forms of this group are symmetric only to the shaded 

 planes of fig. 28. The cube, octahedron, dodecahedron, trisocta- 

 hedron and trapezohedron, which occur in this as well as in 

 the preceding group, are here distinguished by striations, nat- 

 ural etching and modifying faces which clearly show their binary 

 symmetry; as for example the cube of pyrite shown in fig. 45, 

 which occurs striated in the directions of the alternate parallel 

 edges of each square face. 



