HEXAGONAL SYSTEM 



the Scalenohedron and the 

 Rhombohedron of the Mid- 

 dle Edge. 



FIG. 166. Calcite, Com- 

 bination of R (lOll), 



m (loio), v (2131). tant 



commer- 

 impor- 

 minerals 

 belong here. 



Calcite, CaCO 3 , Fig. 166, is a Com- Fro. 167. Hematite, c(0001), 

 lunation of R(10ll),m(10lO),v(2131). 



Hematite, Fe 2 3 , Fig. 167, is a combination of a base and the 

 plus and minus rhombohedron. 



Corundum, A1 2 O 3 ; Siderite, FeCO 3 ; Arsenic ; Antimony ; 

 Brucite, MgO . H 2 O, also crystallize in this type. 



