850 PHYSIOGRAPHY. CLASS II. 



a = V 0-5921. 



Simple forms. R OD (&) ; R 1 (ft) = 1 55 9'; 

 R (P) ; R+l (o) = 103 21'; R + 2 (r) = 

 76 50'; R + oo (/) ; P + oo (*); (P 1) 5 (>); 



(P)* ; (P)* () ; (P + !) ; (P + GO)' (ft). 



Char, of Comb. Hemi-rhombohedral, with different 

 faces contiguous to opposite ends of the crystals. 

 Of the prism R + oo, there are generally only 

 the alternating faces, of (P + oo) m the alternating 

 pairs to be met with in the combinations. 



Combinations. 1. R. [ R + ]. p + pp. R. Sim. 



Fig. 136. Colour black. Greenland. 

 2.R. (P)*. [ R + ] t P + OD. Red. Cathe- 



m 



rinenburg, Siberia. 



3. R. R + l. P + oo. R oo. Fig. 137. Green. 

 St Gotbard. 



4. R oo. R 1. R. 5l^. P + QD. R. 



<v 



Brown. Ceylon. 



5. R oo. R 1. R. E R + *1. R 1. 



2 



R oo. Fig. 138. Red. Ceylon. This va- 

 riety occurs along with dodecahedral Corun- 

 dum, and is remarkable for the face R oo, 

 which occurs on both ends of the crystal. 



6. R 1. R. |II. (P I) 3 . R + l. R + oo. 

 P + oo. Black. Penig, Saxony. Observed 

 only on one end. 



