PHYSIOGRAPHY. 65 



Black Manganese. 



Hardness = 5-0 ... 5*5. Sp. gr. = 4-722 of a crys- 

 tallized variety. 



Compound Varieties. Twin crystals. Common octa- 

 hedral hemitrope ; also repeated a second time, 

 Fig. 61. 



Massive : composition granular, firmly connected. 



1. Before the blow-pipe on charcoal, in a strong heat, it fuses on the 

 edges ami assumes a blackish-grey color. With borax, it is easily dis- 

 solved, giving in the exterior flame an amethystine blue color, and in 

 the interior a feeble tinge of iron. With salt of phosphorus, it dissolves 

 rapidly with effervescence, and attended with a deep blue color, which 

 disappears in the reduction -fire of the instrument. 



2. Analysis. 



It is not absolutely certain that the Black Manganese has as yet been 

 subjected to analysis, although it is extremely probable that the variety 

 of Manganese from Piedmont, analysed by BERZEL.IUS, belongs to this 

 species. It consisted of 



Oxide of manganese .... 75-80 

 Silica . . . . 13-17 



Oxide of iron . . . . 4-14 



Alumina .... 2-80 



3. It has been found in veins in porphyry, along with other ores of 

 manganese, at Ochrenstock, near Ilmenau in Thuringia, and at IhlefeJd 

 in the Hartz. In the United States, it occurs at Lebanon, (Penn.) It is 

 yet a rare substance. 



6* 



