130 MINERALOGY 



CLASS, HOLOHEDRAL (HOLOSYMMETRIC) 

 TYPE 2, CENTROSYMMETRIC 



All forms of this type possess a center of symmetry only and each 

 form is composed of a single pair of parallel faces, Fig. 259. 

 Forms. Pyramids. 



FIG. 259. Type 2, Centrosym- 

 metric. 



Unit series of pyramids, 



FIG. 260. Two Faces forming 

 a Triclinic Pyramid. 



a : b : me, (hkl) . 

 a : b : me, (hkl). 

 a:b:mc, (hkl). 

 a : b : me, (hkl). 



FIG. 261. Two Faces forming a Triclinic Prism. 



