434 CHARACTERISTIC. CLASS It. 



X. TOURMALINE. Rhombohedral. 



H. = 7-0 ... 7-5. 

 G. = 3-0 ... 3-2. 



1. RHOMBOHEDRAL. Rhombohedral. R = 133 26'. 



Combinations, the opposite ends of the crystals con- 

 taining different faces. 

 Cleavage, R. P + os. Imperfect 



Tourmaline. ii. 349. 



XI. GARNET. Tessular, pyramidal, prismatic. 



Lustre, not pure vitreous. 

 H. = 6-0 ... 7-5. 

 G. = 3-1 ... 4-3. 



Colour black : G. = 3 9 and less. 



H. = 7*5 : colour red or brown. 



G. under 3-3 : form tessular. 



1. PYRAMIDAL. Pyramidal. P = 129 29', 74 14'. 



Cleavage, P . os. P + 03. [P + oa]. 



H. = 6-5. 



G. = 3-3 ... 3-4. 



Idocrase. ii. 354. 



2. TETRAHEDRAL. Semi-tessular, with inclined faces. 



Cleavage, octahedron, imperfect. 

 H. == 6-0 ... 6-5. 

 G. = 3-1 ... 3-3.^ 



Helvine. . ii. 357. 



3. DODECAHEDRAL. Tessular. 



Cleavage, dodecahedron, imperfect. 

 H. = 6-5 ... 7'5. 

 G. = 3-5 ... 4-3. 



Garnet. ii. 359. 



., Prismatic. Pr = 70 32'. (I 5 r + ),* 



129 3K 



