oO Chemical Examination of American Minerals. 



It, therefore, is a compound of. 



5 atoms silica, - - - - 10 



4 atoms magnesia, - - - - 10 



3 atoms of water, _ - _ - 3'375 



23.375 



Perhaps it may be considered as a compound of 5 atoms 

 bisilicate of magnesia, and o atoms bihydrate of m.agnesia. 

 The sj/mbol voidd be 5 JV1«S~ -f S MnAq". This view would 

 accord with the constituents found, were we to consider the 

 iron as an accidental ingredient. 



16. BISILICATE OF MAGNESIA. 



The mineral, which from its composition 1 distinguish by 

 the name of bisilicate of magnesia, was sent me from Bolton, 

 Massachusetts, by Mr. Nuttall. It bears so much resemblance 

 to the pitrosmine of Haidinger, both in its character and 

 composition, that I strongly suspect the two minerals will 

 turn out mere varieties. 



The bisilicate of magnesia has a white colour, with a 

 slight shade of green. Its powder is white. 



It consists of a congeries of prismatic crystals very irregu- 

 larly disposed, and so involved in each other, that the shape 

 cannot be distinctly made out. The few faces which were 

 tolerably distinct, lead to the notion that the crystals are 

 four-sided oblique prisms. 



Lustre glassy. Translucent on the edges. 



The crystals cleave longitudinally, but in no other direc- 

 tion. 



Scratched by the knife, but not easily. 



Specific gravity 2'976. 



The constituents of this mineral are, 



