126 



PHYSIOGRAPHY. 



Pyrochlore Pyrolusite. 



1. Alone, it becomes of a clear, yellowish brown color, and melts with 

 much difficulty, into a blackish-brown, slaggy mass. With borax, it is 

 perfectly dissolved in the oxidation fire, into a reddish-yellow, transpa- 

 rent glass, which, by flaming, becomes yellow and opake. In the redu- 

 cing heat, a dark red pearl is obtained. In salt of phosphorus, it is dis- 

 solved perfectly, attended at first, with some effervescence. With soda, 

 upon platina, it affords a green manganesious reaction. 



2. Analysis. 

 By WOHL.ER. 



Titanic acid 62-75 



Magnesia ...... 12-85 



Protox. of uranium . . . . . . 5 18 



Oxide of cerium (impure) 6-80 



Oxide of manganese 2-75 



Oxide of iron . . . . . 2-16 



Oxide of tin 0-61 



Water 4-2Q 



3. It is found at Friederichsvairn in Norway. 



PYROLUSITE. Prismatic Manganese-Ore. 

 HAIJDINGER. 



Primary form. Right rhombic prism. M on M = 93 

 40'. 



Secondary form. 



Fig. 346. 



M 



M 



Cleavage, parallel to M and b. 



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

 lumnar compositions, the color becomes bluish, and the lus- 

 tre imperfectly metallic. Streak black. Opake. 



