Chemical Examination of American Minerals. 29 



smooth for accurate measurements. Judging from a small 

 fragment which I lately received from Dr. Torrey, the figure 

 may be a right oblique prism. 



The specific gravity of the mineral in its natural state is 

 3*44. When it had been digested in muriatic acid till it be- 

 came white, its specific gravity was 8*483. > iij 



A portion of the mineral was treated with muriatic acid, 

 till it assumed a white color. Much chlorine was evolved, 

 and nearly one fourth of the mineral was dissolved. From 

 the solution I obtained, 



Deutoxide of manganese, - - - - 17*716 

 Peroxide of iron, _ - _ _ _ 6*480 



The white residue was composed of, 



Silica, 29*48 



Protoxide of manganese, - - - - 34*64 



Peroxide of iron, _ - . _ _ 5.74 



Moisture, -...__ 3-17 



98-226 



There can be no doubt that the mineral has undergone a 

 species of decomposition externally from the action of the air ; 

 the protoxide of manganese having been converted into deut- 

 oxide. Originally its constituents seem to have been. 



Silica, 29-48 



Protoxide of manganese, - . - _ 50-584 



Peroxide of iron, _____ 13'22 



Water, _______ 3.17 



So that originally, it must have been a compound of 4 

 atoms silicate of manganese, and 1 atom persilicate of iron. 



The white residue, were we to consider the peroxide of iron 

 as foreign, would be a bisilicate of manganese. But this 

 supposition is not likely to be the true one. 



