DESCRIPTION OF THE DICHROIT. $31 



The results of the analysis are 



Silex 42*5 Component 



Alumina 11-5 P"''' 



Magnesia....* 9 



Oxide of iron 22 



« — -— ^ — -manganese .••• 2 



Potash 10 



Loss by calcination • 1 



98. 



From what has been said we may conclude: 



1. That pure talc contains magnesia, and no alumine, Difference h&*^ 



which is a decided characteristic of this stone. *^.°®" ^^^^ *^^ 



mica. 



2. That common mica contains alumine, and no mag* 



nesia. 



0' That Muscovy glass differs from common mica by its 

 refractoriness, its larger proportion of alumine, its smaller 

 proportion of oxide of iron, and its containing a trace of 

 magnesia, 



4* That the black mica of Siberia deserves to be consi- 

 dered as a variety differing both from conimon mica and 

 Muscovy glass by its proportions of alumine and magnesiaj 

 as well as by its larger proportion of oxide of iron. 



5. That raica, and its different varieties, are to be reck- 

 oned among the richest of the potassiferous minerals. 



XI. 



Stescripiion of the Dkhroity a new Species of Mineral: b^ 

 Mr. L. CoiiDiER, Mine Engineer in Chief ^^ 



JL HE mineral I am about to describe belongs to the class Mbiefolpov 

 of earthy substances. Its proper place in a system appears p,p^fiy 

 to be next the emerald ; and it would not be more remark- 

 able than most species of the same class, if it were not 



♦ Abridged from the Jaurnal des Mines, toI. XXV, p. 129. 



endued 



n»tr 



