MINERALOGY 



II. Tetragonal prism of the third order; 



no 



; IT (hko) 



IT (hko). 



If the pole be placed on the primitive circle in an asymmetric 

 position in the octant, or if every other face of the ditetragonal 



FIG. 135. Prism of the Third Order 

 of Stolzite, T (340). 



FIG. 135 a. Combination of the 

 First Order Prism with the Third 

 Order Pyramid. 



prism is extended, a new form will result, the tetragonal prism of 

 the third order, Fig. 135, similar in shape to the 1st and 2d order 

 prisms, except the lateral axes end in the face between the center 

 of the face and the middle of the edges. 



All other positions of the pole will yield 

 holohedral shapes. 



The possible forms in combination will 

 therefore be the 



Positive and negative pyramids of the 3d 

 order, IT (hkl) TT (hid). 



Tetragonal pyramid of the 1st order, (hhl). 

 Tetragonal pyramid of the 2d order, (hoi). 

 The positive and negative prism of the 3d 

 order IT (hko), (hko). 



Tetragonal prism of the 1st order, (hho). 



FIG. 136. Combination _., , . P , i r i j / t- \ 



of (ioi) (ill) and (313) Tetragonal prism of the 2d order, (oho), 

 of Scheeiite. Basal pinacoid, (001). 



