360 Mr. T. S. Hunt's Examinations of some Felspathic Rocks. 



and may be an inch or two apart, while those of ilinenite are 

 still thinner, and often enclosed in the pyroxene, along the sur- 

 faces of which deep red grains of garnet are occasionally seen. 

 These different minerals appear in relief upon the white weathered 

 surface of the rock, and give a picture of its stratified structure, 

 which is, however, not less apparent upon the surfaces of recent 

 fracture. Small, rounded, bluish masses of cleavable felspar are 

 frequently disseminated in the same planes as the other minerals. 

 In some places the pyroxene appears to pass into, or is replaced 

 by, foliated hypersthene. A homogeneous fragment of this rock 

 from Rawdon had a density of 2-691. It was bluish- white, gra- 

 nular and translucent, and gave by analysis, — 



XII. 



Silica 54-45 



Alumina 28-05 



Peroxide of iron '45 



Lime 9'68 



Potash 1-06 



Soda 6-25 



Loss by ignition .... "55 



100-49 

 In connexion with this variety, which has nearly the compo- 

 sition assigned to labradorite, I may give the analyses of two 

 felspars which differ from it principally in their greater amount 

 of lime. No. XIII., from the township of Morin, belongs to 

 the same area as the last, and forms large cleavable masses in a 

 fine-grained base. Its density is 2'684i to 2-695, and its colour 

 greenish-gray, passing into bluish-gray, with an occasional pearl- 

 gray opalescence. The greenish paste of this felspar is softer 

 than the others, and yields with effervescence about four hun- 

 dredths of carbonate of lime to dilute acids ; the insoluble residue 

 has nearly the composition of the felspar. No. XIV. is a clea- 

 - vable, lavender-blue, opalescent variety, from a rolled mass found 

 in Drummond, Canada West, and having a density of 2'697. 

 The determination of the alkalies in this was not made by the 

 same process as in the other analyses, and probably does not 

 give the full amount. 



XIII. XIV. 



Silica 54-20 5470 



Alumina .... 29-10 29-80 



Peroxide of iron . 1'10 -36 



Lime 11-25 1142 



Magnesia . . . '15 traces 



Potash "1 , Vtt 3-80 -23 



Soda } b y<" ff - ... 2-44 



Loss by ignition . "40 *40 



10000 9935 



