136 Mr HAIDINGER'S Mineralogical Account of 



V. PRISMATIC MANGANESE-ORE. 

 Pyrolusite. 



Grau Braunstein, in part, Hausmann, p. 288. Fasriger Schwarz - Braunstein, 



Id. p. 293. 



Grey Manganese-ore, in part, Jameson, vol. iii. p. 252. 

 Grey Oxide of Manganese, in part, Phillips, p. 243. 

 Mangan-Hyperoxid, Leonhard, p. 240. 



Form and cleavage probably belonging to the prismatic sys- 

 tem ; the cleavage taking place in several directions. 



Lustre metallic. Colour iron-black ; in very delicate columnar 

 compositions the colour becomes bluish, and the lustre imperfect 

 metallic. Streak black. Opaque. 



Rather sectile. Hardness n 2.0 ... 2.5. Sp. gr. =. 4.94, a 

 specimen from Elgersburg, and another, locality unknown, =. 

 4.819, according to Dr TURNER. 



Compound Varieties. Reniform coats. Both columnar and 

 granular composition is often met with, particularly the former ; 

 the individuals often radiating from common centres. If the in- 

 dividuals are very delicate, the masses will soil the ringers, and 

 write on paper. 



Observations. 



The name of Pyrolusite alludes to a property, for which this 

 mineral is reckoned the most valuable one among the preceding 

 species. It is derived from trvg, fire, and Xov/u, I wash, being em- 

 ployed, in consequence of the large quantity of oxygen which it 

 emits at a red heat, to free glass from the brown and green tints 

 produced by carbonaceous matter and protoxide of iron. The 



