PHYSIOGRAPHY. 



Manganite. 



Fig. 289. 



gong- - - 172 

 cone - - 115 

 n on n - - 95 



m on m 

 I on I 

 r on r 



- - 112 35' 



- - 51 18 



- - 134 14 



Cleavage,, parallel with / highly perfect, and easily ob- 

 tained; with M also perfect, but less easily obtained; traces 

 of r. Fracture uneven, surface of the vertical planes streak- 

 ed parallel to their common edges of intersection. In gen- 

 eral, the faces are smooth, and possess pretty high degrees 

 of lustre. 



Lustre imperfectly metallic. Color dark, brownish black, 

 inclining to iron-black. Streak, reddish brown. Opake 

 in larger masses ; when broken, or cleaved in the direction 

 of /, and exposed to the light of the sun, minute splinters 

 are often observed, which, by transmitted light, appear of a 

 bright, brown color. 



Brittle. Hardness =4-0 . . . 4-25.* Sp. gr. = 4*328, 



* In the description given above, the streak of the crystals is stated to 

 be reddish brown. It is very often the case, however, that crystals 

 are met with, and still more frequently compound varieties, consist- 

 ing of columnar individuals, which actually afford a black streak. The 

 hardness of these varieties is much inferior to that of the crystals which 



