Chemical Examinaiion of American Minerals. 47 



14. PHYLLITE. 



I have given this name to a mineral which T received about 

 a year ago from Mr. NiUtall, from Sterling, in Massachusetts. 

 The color of one portion composed of flat micaceous scales, 

 is brownish-black ; but the greatest part consists of thin bent 

 plates, having a bluish-gray color, and no bad resemblance 

 to plumbago in its appearance. 



The lustre is shining and resinous, or rather semi-metallic. 



Feel greasy. 



The flat brown plates are so hard as not to be scratched by 

 the knife, and not easily by quartz. But the plumbago-look- 

 ing portion (which constitutes almost the whole specimen) 

 is so soft, that it may be scratched by the nail of the finger. 



Sectile. 



Specific gravity 2-S89. 



The constituents of the plumbago-looking portion of this 

 mineral, were found to be, 



Silica, _ - . . . 38-40 



Alumina, ----- 23-68 



Peroxide of iron, - _ _ _ 17-52 



Magnesia, ----- 8-96 



Potash, - . - . - 6-80 



Water, ----- 4-80 



100-16 



It seems to consist of, 



1 atom silicate of potash, 



2 atoms bisilicate of magnesia, 

 3i atoms silicate of iron, 



11 atoms silicate of alumina. 



Were we to suppose the silicates of potash and magnesia 

 to be extraneous, the mineral would be a compound of. 



