Chemical Examination of American Minerals. 53 



The constituents of paulite are, 



Silica, _ _ - - - 



Magnesia, - - - - - 



Peroxide of iron, _ - . - 



Protoxide of manganese, _ _ - 



Lime, _ . - - - 



Alumina, _ _ - - - 



Water, - _ . - - 



101-316 



The constituents of Isle of Skye hypersthene, were found 

 to be, 



Silica, ------ 51-348 



Magnesia, 11-092 



Peroxide of iron, . - - - 33-924 



Lime, ------ 1*836 



Water, - - - - - - 0-500 



98-700 



Notwithstanding the difterence between these two analyses, 

 there seems no reason to doubt the two minerals belonging to 

 the same species. The hardness of both is the same ; their 

 specific gravities very nearly agree ; and so do ilieir crystal 

 line forms, as far as they have been determined. It is obvious 

 that the constituents of h\perstene, like those of pyroxene 

 and amphibole, are not constantly the same. The manga- 

 nese and alumina being wanting altogether, and the lime 

 vei-y nearly, in the Isle of Skye hypersthene ; perhaps we may 

 be permitted to consider them as only accidental ingredients. 

 In that case the essential constituents will be silica, magnesia, 

 and peroxide of iron. The number of atoms of silica in the 

 mineral, '\' tv'cp as great as that of the magnesia and per- 

 oxide of iron taken together. Hence, it is clear that hyper- 

 sthene consists of bisilicate of magnesia and peroxide of iron 



