430 CHARACTERISTIC. CLASS II. 



VII. ORDER. GEM. 



I. ANDALUSITE. Prismatic. 



Cleavage not pr is mate-id al. 



H. = 7-5. 



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



1. PRISMATIC. Prismatic. 



Cleavage, P + oo = 91 33'. r +00. Pr + oa. 



Andalusite. ii. 293. 



II. CORUNDUM. Tessular, rhombohedral, pris- 



matic. 



H. = 8-0 ... 9-0. 

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



Prismatic : G. =. 3-65 and more; H. = 8-5. 



Colour red or brown ; G. = 3-7 and more : 

 H. = 9-0. 



1. DODECAHEDRAL. Tessular. 



Cleavage, octahedron, difficult. 



H. = 8-0. 



G. = 3-5 ... 3-8. 



Spindle. ii. 295. 



2. OCTAHEDRAL. Tessular. 



Cleavage, octahedron, perfect. 



H. = 8-0. 



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



Gahnite. ii. 298. 



3. RHOMBOHEDRAL. Rhombohedral. R = 86 6'. 



Cleavage, R. Sometimes, R w. 



H. = 9-0. 



G. = 3-9 ... 4-05. 



Corundum. " 299. 



