46 



NEW YORK STATE MUSEUM 



Table 3 Thin sections of Keene gneiss 



No. 27, one-half of a mile north-northwest of Bailey pond; no. 29, 

 just north of the granite by the trail 2 miles northeast of Bailey pond; 

 no. 30, r mile northeast of Bailey pond; no. 33, eastern slope of Bailey 

 hill; nos. 36, 362 and 38, southern brow of Cobble hill; no. 46, just south 

 of the brook I mile east of Hewitt pond; no. 48, one-fourth of a mile south 

 of the mouth of Hewitt pond brook. 



Descriptions of occurrences in the Schroon Lake quadrangle. 

 Most of the Keene gneiss of the quadrangle occurs in the two 

 largest areas separately mapped as such, but in the areas mapped 

 as anorthosite and syenite-granite mixed rocks, there are many 

 excellent local developments, and certain of these will be con- 

 sidered first. 



An outcrop on the southern brow of Cobble hill, i mile due south 

 of Bailey pond, is very significant because of the light it throws 

 upon the local origin of the Keene gneiss. The accompanying 

 sketch (figure 3) shows the relationships. This Keene gneiss is 

 distinctly granitic or syenitic in appearance except for the many 

 labradorite crystals, mostly an inch long, which stand out as 

 phenocrysts more or less parallel to the crude foliation of the 

 otherwise medium grained rock. Nos. 36, 36a and 38 represent 

 thin sections of this Keene gneiss which, though variable, is dis- 

 tinctly intermediate between the granite and the anorthosite in the 

 same ledge. Within this Keene gneiss there are inclusions of 

 Whiteface anorthosite (no. 37 of table i) which contain some 

 large labradorites and also scattering femic minerals up to 2 inches 

 long, more or less lenslike and parallel to a distinct foliation. Con- 

 tacts between the inclusions and the Keene gneiss are not very 



