$l8 ANALYSIS OF COMPACT FELSPAR 



the floetz formation which we have just mention- 

 ed. 



As this rock is interesting in an economical, as 

 well as mineralogical point of view, being em- 

 ployed as an ingredient in porcelain, I was in- 

 duced to undertake its analysis, and performed it, 

 about three years ago, in Dr Thomson's laboratory, 

 with as much attention to accuracy as possible. 



The analysis was conducted in the usual way. 

 Hence it is not necessary to particularize the ex- 

 periments. The constituents obtained were the" 



following : — • 





Silica, 



71.17 



Alumina, 



13,60 



Lime, 



0.40 



Iron, 



1.40 



Manganese, 



O.IO 



Potash, 



3-19 



Volatile matter, 







1 



93-36 





Loss, 6.64 





1 03. 00 



This result approaches very nearly to a previous 

 analysis of common felspar by Vauquelin. Our 

 compact felspar agrees very nearly in its compo- 

 sition with the variety known to the Chinese un- 

 der the name of petunse, which forms a principal 



