GEOLOGY OF SARATOGA SPRINGS AND VICINITY 



25 



Orthoclase 



22.24^ 



Albite 



36.15 



Anorthite 



6.9s > 



Quartz 



28.80 



Corundum 



0.20^ 



Hypersthene 



2.60^ 



Magnetite 



1 .62 



Ilmenite 



0.76 f 



Apatite 



0.17J 



The norm of the rock of analysis i is as follows : 



Class I, persalane 



94.34 Order 4, britannare 



Rang 2, toscanase 



Subrang 4, lassenose 



5-15 



K,0: Na,0 :: 3:5.2 



The northwestern New York granites belong in subrang 3, tosca- 

 nose. while the Ontarian rock is a distinct lassenose. The Sara- 

 toga rock is on the border between the two subrangs as the alkali 

 ratio show's. 



The rock differs considerably in appearance from the usual 

 Laurentian granite of Canada and northern New York, the chief 

 differences being the white color and the content of pink garnet. 

 In the Thousand Islands region we have shown that the red Lau- 

 rentian granites have their red feldspars bleached to white in the 

 vicinity of Grenville limestones.^ We have seen similar bleached 

 granites in Ontario in like situation. About Saratoga the granite 

 masses are small and suggest that erosion here is just beginning to 

 uncover a granite bathylith and has reached only a few of the 

 higher protuberances, full of included rock masses. This might 

 suggest that the granite would run into red rock in depth, but the 

 matter is not urged since the chief inclosing rocks are schists which 

 are poor in lime. 



Because it gives rise to pegmatites and has the comj^osition of a 

 granite, this rock is regarded as igneous. It is further regarded 

 as Laurentian for two reasons : hrst, because it is distinctly older 

 than the syenite which cuts it intrusively just as it cuts the Gren- 

 ville ; and second, because it also shows its great age by the intricate 

 manner in which it is involved with the Clrenville and has been 

 metamorphosed in common with it. in the latter respect it fur- 

 nishes a strong contrast with the Laurentian granites of north- 

 western New York, whose relations with the Grenville are much 

 less involved and more obvious. This contrast is to be attributed 

 to the fact that the Precambric rocks of the Adirondacks show a 



IN. Y. State Mus, Hul. 145. }>. 46-;, i;;-i8o. 



