44 NEW YORK STATE MUSEUM 



The small area three-fourths of a mile north of Loch Muller 

 shows good exposures of hornblende and hornblende-garnet 

 gneisses shot through by some dikes of granite. Some of the garnets 

 up to I or 2 inches in diameter have distinct rims of hornblende. 



In the small area three-fourths of a mile northwest of Loch 

 Muller, hornblende gneiss (metagabbro?) is shot through by granite 

 and considerable magnetite is associated with the rocks. 



Of the small areas west and southwest of Charley hill, the two 

 farthest out are chiefly granite with considerable intermixed 

 older dark gneisses, while the one nearer Charley hill is chiefly 

 well-bedded hornblende gneiss shot through by irregular dikes of 

 granitic syenite. 



The small area i mile south-southwest of South Schroon is 

 mostly hornblende gneiss intricately cut into, and apparently more 

 or less assimilated by, granite. 



The area of about one- fourth of a square mile i mile west of 

 Schroon Lake village shows many good exposures of hornblende 

 and hornblende-garnet gneisses, some very intimately associated with 

 granite in the form of small streaks and bands, and some less inti- 

 mately associated in bodies of considerable size. 



An exposure by the road 1^2 miles a little north of west of 

 Schroon Lake village consists of very gneissoid to almost barided 

 intimately mixed dark gneiss and granite. 



The small area i mile northeast of South Schroon contains very 

 gneissoid syenite or granitic syenite more or less intimately asso- 

 ciated with Grenville hornblende and pyroxene gneisses. 



Hornblende gneiss and syenite are associated in the area on the 

 west side of Thurman pond. 



Keene Gneiss 



General statements. One of the most interesting rock types 

 of the region is locally developed as belts or irregular bodies along 

 or near portions of the borders between the anorthosite and the 

 syenite-granite series. Both the Marcy and Whiteface types of 

 anorthosite show such border rocks. There is very strong evi- 

 dence, based upon field work and a study of thin sections, that this 

 is really a transition rock between anorthosite and syenite or 

 granite formed by actual digestion or assimilation of anorthosite 

 by the invading syenite-granite magma along portions of its borders. 

 The writer has proposed that this rock be called " Keene gneiss," 

 because a fine exposure of the typical fresh rock occurs by the 



