﻿GEOLOGY OF THOUSAND ISLANDS REGION 



177 



reversed in the two. Calculation of its norm gives the following 

 result : 



Or ... 



. 31.69/ 





Class 1, persalane 



Ab ... 



. 26.20 







An ... 



. 5.00 



^95-29 



Order 4, britannare 



Co ... 



• 1.50 







Qz ... 



. 30.40J 





Rang 2, toscanase 



Iiy . . . 



11 & Mt . . . 



. 2.46 

 . i.q8 



I 4-44 



Subrang 3, toscanose 



The rock of analysis 5 was not the normal acid granite gneiss of 

 the locality where it was collected,, but somewhat darker colored, 

 more basic in appearance, and the field relations definitely suggested 

 that it had soaked up some amphibolite. Nevertheless the analysis 

 shows that this contamination is in slight amount, and the rock is 

 to be classified in the same group as its predecessor, as its calcu- 

 lated norm shows. 



Or .. 

 Ab .. 

 An .. 

 Co .. 

 Qz .. 



Hy .. 



II & Mt . . 



Py... 



93-85 



5-49 



Class 1, persalane 

 Order 4, britannare 

 Rang 2, toscanase 



Subrang 3, toscanose 



The mode of these rocks differs so little from the norm that it is 

 not thought worth while to present the calculation. Both rocks con- 

 sist chiefly of feldspars and quartz, with biotite as the principal 

 additional mineral, a little magnetite, and trifling amounts of apatite, 

 zircon, titanite, muscovite and pyrite. These minerals taken to- 

 gether only amount to about 6f e in the first case and 8# in the second. 

 In each case the surplus of alumina in the norm, calculated as 

 corundum, is in just the proper amount to combine with the 

 magnesia to form biotite. 



Bleached granite 



The rock of analysis 1 is from the margin of a small granite 

 boss-cutting limestone, north of Redwood, which we regard as being 

 of Laurentian age, and is a fresh sample of granite whitened by 

 adjacent limestone. It is a somewhat more acid rock than the 

 preceding. Unfortunately no samples which seemed satisfactory 



