70 Chemical Examination of American Minerals. 



I got a specimen of this mineral about fourteen years ago, 

 from Mr. Suedensijerna. It occurs in Eric Matt*'s mine at 

 Fahlun, n)ixed with the dark-green fahlunite, and is always 

 amorjjhous. 



The color is yellowish-brown. 



The lustre is waxy. 



Priiicipal fracture foliated; cross fracture granular. 



Trau>li!cei!t when in ;hni pieces. 



Scratched by quartz, but not by the knife. 



Specific gravity 2 6.32. 



Brittle. Tough. 



Wlien analyzed its constituents were found to be, 



Silica, 51-840 



Alumina, ------ 24-780 



IVJaguesia, _____ 7 704 



Protoxide of iron, - _ - _ 10-296 



Protoxide of manganese, - _ _ 2-248 



Lime, _-_--_ 2-684 



Water, ------ 0-576 



100128 



This analysis differs considerably from those of Hisinger 

 and Stromeyer, showing clearly that fahlunite, if it be a pe- 

 culiar species, does not occur at Fahlun in a state of purity. 

 Stromeyer considers hard fahlunite as a viirietv of dichroite. 

 This conclusion is dedit< ed from the analysi? ; the minera- 

 logical characters are too imperfectly marked to warrant any 

 conclusion. 



25. SPINELL AND CEYLANITE. 



Though the nature of the rock in which the spinell occurs, 

 has not been made out in a satisfactory manner, yet there 

 seems no reason to doubt that it belongs to the primary 

 rocks. I have specimens of primitive limestone from Sweden, 



