168 



PHYSIOGRAPHY. 



Rutile. 



Cleavage parallel with M perfect, with d interrupted. 

 Fracture conchoidal, uneven. Surface, a and c, either 

 smooth or rough, but both of the same quality ; d, e and M 

 vertically streaked. 



Lustre metallic-adamantine. Color reddish brown, pas- 

 sing into red, sometimes yellowish. Streak very pale- 

 brown. Translucent . . . opake, sometimes in a strong light, 

 transparent. 



Hardness =6-0 . . . 6-5. Sp. gr. =4-249. 



Compound Varieties. Twin-crystals very frequent, ax- 

 is of revolution perpendicular, face of composition parallel 

 to face a. The composition produces geniculated groups, 

 and is often repeated in several geniculations, as in fig. 

 387. 



Fig. 386. Fig. 387. 



Thin and long individuals, produce after this law, a re- 

 ticulated composition. Massive, composition granular, the 

 individuals being of various sizes and strongly connected. 



1. Alone before the blow-pipe, it is infusible, but gives with borax in 

 the reducing flame a yellow glass, which assumes an amethyst-color, 

 when farther reduced. 



2. Analysis. 



If pure, it is entirely composed of oxide of titanium, which according 

 to ROSE, consists of metal 66-05, and of oxygen 33-95. 



