32 NEW YORK STATE MUSEUM 



pegmatite. In some ledges nearly pure, pink, moderately coarse- 

 grained granite predominates. 



Interesting exposures of Grenville-granite mixed rocks occur on 

 the steep hill just north of Lake Luzerne. At the top big ledges 

 show the rock to be dark gray, garnetiferous, biotitic gneiss asso- 

 ciated with a little amphibolite all cut to pieces by granite and peg- 

 matite. This clearly foliated mixed rock contains some distinct 

 lenses of Grenville gneiss up to 8 inches wide and over a rod long 

 parallel to the foliation, which latter is mostly wavy and locally even 

 contorted. There are many narrow bands of pegmatite and silexite 

 rarely more than a few feet long and a few inches wide. Some of 

 these are distinctly dikelike, but most of them have (under pres- 

 sure) been kneaded into the contorted rocks. Most of the peg- 

 matite and silexite masses are roughly parallel to the foliation, and 

 many pegmatites contain garnets which more than likely represent 

 material absorbed from the garnetiferous gneiss. In the road metal 

 quarry at the southwestern base of the hill somewhat similar rock 

 is exposed. This rock bears a strong resemblance to facies of the 

 granite porphyry above described and lends support to the view 

 that the porphyry really represents old dark gneiss which has been 

 thoroughly injected and possibly digested by much granite magma. 



Grenville-granite mixed rocks very similar to those last described 

 also make up the small area on Bucktail mountain, and along the 

 middle eastern border of the quadrangle. 



The mixed rocks of the small area ij^ miles northeast of Stony 

 Creek village consist mainly of Grenville green pyroxene gneiss and 

 quartzite cut rather irregularly by some granite and considerable 

 pegmatite. 



The area covering about i square mile between 2 and 3 miles 

 north of Stony Creek village consists very largely of a rather 

 heterogeneous mixture of Grenville light-gray to dark garneti- 

 ferous, biotitic, and hornblendic schists and gneisses more or less 

 intricately cut and injected by considerable granite and pegmatite. 

 These rocks are mostly well banded with variable strike and dip. 



The area of Grenville-granite mixed rocks north of Thurman 

 station is the southern extension of a larger area in the North 

 Creek quadrangle. Within the Luzerne quadrangle there are rela- 

 tively few exposures representing various types of Grenville in- 

 volved with granite. Near the mouth of the main brook of the 

 area, Grenville hornblende gneiss is cut by considerable granite. 

 Nearly one-half of a mile up this broolc a ledge 100 feet long shows 



