42 Chemical Examination of American Minerals. 



The color of the mineral is grayish-white, with a very 

 slight tint of yellow, not recognizable in the purest portions of 

 the mineral. 



It is composed of fibres, which in some places appear 

 curved, and when viewed by a microscope, assume the ap- 

 pearance of plates, or imperfect crystals. 



Lustre silky. 



Not scratched by quartz, and with difficulty by topaz; 

 but easily by sapphire. 



Brittle. Easily frangible. Fragments sharp-edged. 



Specific gravity 3-193. 



The constituents of this mineral were found to be, 



Silica, _ . _ - . 46-40 



Alumina, ----- 52-92 



99-32 



It is, therefore, a silicate of alumina, composed of, 



1 atom silica, - - - - - 2 



1 atom alumina. - - _ _ 2-25 



4-25 



Brandes' analysis gave, 



Silica, ------ 46 



Alumina, ------ 50 



Protoxide of iron, ----- 2*5 



Potash, ------ 1-5 



100 



It is obvious that the American specimen which I analyzed, 

 was purer than Brandes's. My loss being only O-t-S per cent, 

 I did not search for potash. If any is present, which I be- 

 lieve there is not, it must be a mere trace. 



Note. Although the American variety of this mineral is 

 now described for the first time, it has been well known to all 



