/ 



Chemical Examination of American Minerals. 27 



surement of a more perfect specimen, which I have just re- 

 ceived from Dr. Torrey, gives about 86° &; 94°. These 

 measurements were with the common goniometer. There is 

 a third cleavage much less distinct, but seemingly rectangular 

 to the edges of the prism. Hence the primary form may be 

 a right oblique prism, with angles deviating 3° or 4° from 

 right angles. 



Lustre shining and vitreous. 



Hardness nearly the same as that of felspar. It cannot be 

 scratched by the knife. 



Specific gravity 4*078. 



Powder light red. Becomes brown by ignition, and loses 

 2*7 per cent, of its weight. 



When digested in diluted muriatic acid, it gradually dis- 

 solves without any effervescence. Its constituents were found 

 to be, 



Silica, 29-64 



Protoxide of manganese, _ - - - 60*60 



Peroxide of iron, _ _ . _ - o*92 



Moisture, 2*70 



99-86 



If the iron and moisture be accidental ingredients, the 

 mineral is a simple silicate of manganese, composed of, 



1 atom of silica, ----- 2 



] atom protoxide of manganese, - - - 4-5 



6-5 



I think it not impossible, that this mineral may have been 

 previously observed by mineralogists, but confounded with 

 carbonate of manganese. Never having seen a specimen of 

 native carbonate of manganese, I am ignorant of its charac- 

 ters ; nor have I seen any description of it that seems entitled 

 to confidence. 



