304 Mr Haidinger's Description of Pyrolusite, 



changes. Much, very much, is to be looked for in the im- 

 provement of this thermometer. At some future period I may 

 perhaps resume this subject. In the meantime, I remain your 

 most obedient servant, 



A 



Art. XVIII. — Description of Pyrolusite, or Prismatic Man- 

 ganese Ore. By William Haidinger, Esq. F. R. S. E. 



As Mr Haidinger's valuable paper on the manganese ores 

 was drawn up for this Journal, and first published in it, we 

 propose to lay before our readers an account of Pyrolusite, or 

 Prismatic Manganese Ore, which has been established as a 

 new mineral species since the publication of that article. It is 

 given by Mr Haidinger in his enlarged paper on the ores of 

 Manganese in the Edinburgh Transactions. 



Prismatic Manganese-Ore. 

 Pyrolusite. 

 Grau Braunstein, in part, Hausmann, p. 288. 

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



Form and cleavage probably belonging to the prismatic 

 system ; the cleavage taking place in several directions. 



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

 lumnar compositions the colour becomes bluish, and the lustre 

 imperfect metallic. Streak black. Opaque. 



Rather sectile. Hardness = 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 individuals are very delicate, the masses will soil the 

 fingers, and write on paper. 



Observations. — The name of Pyrolusite alludes to a pro- 

 perty, for which this mineral is reckoned the most valuable 

 one among the preceding species. It is derived from irZ^fire, 

 and Xoboj, I wash, being employed, in consequence of the large 

 quantity of oxygen which it emits at a red heat, to free glass 



4 



