Da T. THOMSON'S Analysis of some Minerals. 443 



There is a slight excess, which would be diminished by re- 

 ducing the peroxide of iron and the red oxide of manganese 

 to protoxides ; for that is the state in which they probably 

 exist in the mineral. This reduction being made, the consti- 

 tuents of the mineral will be 



Silica, . . . ... 29.60 



Protoxide of iron, . . 68.605 

 Protoxide of manganese, 1 .857 



100.062 

 This is equivalent to 



14.8 atoms silica, 

 15.24 atoms protoxide of iron, 

 6.40 atoms protoxide of manganese. 



If we admit the 0.4 oxide of manganese to have been united 

 with 0.4 protoxide of iron, there will remain 



14.8 atoms silica, 



14.8 atoms protoxide of iron. 



It is obvious from this that the mineral is a simple anhydrous 

 silicate of iron, composed of 



,. ;- ,-r U f,-/ . r 



1 atom silica, . . . ,V . 2 



^ 1 atom protoxide of iron, . 4.5 



6.5 



This mineral adds another species to the family of silicated 

 iron already so numerous ; though there can be little doubt 

 that many more species will be added hereafter. The following 



VOL. XI. PART II. 3 K 



