HEXAGONAL SYSTEM 



Upper and lower base, ooa: ooa: ware; (oooi), (oooi). 

 Examples. Greenockite, CdS, Fig. 171, is a combination of five 

 tonne. 



Iodide of Silver, Agl, Fig. 172, is a top-shaped combination of 

 an upper and a lower hemipyramid with the first order prism. 



Fia. 171. Greenockite, a 

 Combination of p (lOTl), 

 p(10fl), m (1010), z (2021), 

 c(OOOT). 



FIG. 172. m (1010), p(1011), 

 z (2021). 



Wurtzite, ZnS, and Zincite, ZnO, are other minerals which 

 crystallize in this type. 



CLASS, HEMIHEDRAL PYRAMIDAL (PARALLEL-FACED HEMIHEDRONS) 

 TYPE 17, HEXAGONAL EQUATORIAL 



Symmetry. Crystals of this type are symmetrical in regard 

 to one axis of hexagonal symmetry, the c axis, one plane of sym- 



FIG. 173. Type 17, Hexagonal 

 Equatorial. 



FIG. 174. 



