7G 



Chemical Examination of Heulandite. 



by Mr. Brooke, in the Edinburgh Philoso- 

 phical Journal, vol. vi. p. 1 12. The summit of 

 the crystal constituting the face P, has a fine 

 pearly lustre, while that of the other faces is 

 glassy. The lustre is splendent. 



Color snow white. 



Structure foliated. Cleaves easily parallel to the summit. 



Scratched by the knife ; the pearly face easily ; the other 

 with more difficulty. 



Specific gravity 2* 195. 



Its constituents were found to be, 



Silica, - - - - - 59-144 



Alumina, - - - . _ 17-920 



Lime, - - _ _ _ 7-652 



Water, - - - - - 15-400 



100-116 



By Walmstedt's analysis, as given by Berzelius,* the con- 

 stituents are, 



Silica, - 

 Alumina, 

 Lime, - 

 Water, 



59-99 



16-8T 



7-19 



13-43 



97-39 



So that its constitution is, 



1 atom tersilicate of lime, 



4 atoms tersilicate of alumina, 



7 atoms water, 



9-S 

 33-0 

 7-875 



50-375 



* Edin. Phil. Jour. vii. 1 1 . 



