52 NEW YORK STATE MUSEUM 



syenite-granite mixed rocks. Enough outcrops were observed to 

 render it certain that practically all this area was originally White- 

 face anorthosite which was intruded, and more or less cut to pieces, 

 by the syenite-granite magma. Many individual outcrops are either 

 anorthosite or syenite or granite clearly recognizable as such, but 

 here and there local assimilation has taken place resulting in the 

 development of some Keene gneiss. In a few cases the rocks are 

 admittedly of doubtful origin. Some portions of the area show 

 few if any exposures as, for example, north and northeast of 

 Bailey pond, and in the valley between Hayes mountain and Cobble 

 hill. In view of the facts just stated, it has seemed impossible 

 to represent satisfactorily the various rock types on the geologic 

 map. A few occurrences of particular interest will be described. 



Perhaps the most interesting occurrence in the area just men- 

 tioned is at the summit of Cobble hill and in the belt containing 

 Keene gneiss which extends east-west for fully one-fourth of a 

 mile across the southern brow of the hill (see page 46). Sur- 

 rounded by typical granite, there are inclusions of Whiteface anor- 

 thosite, most of them not more than a few feet long, arranged 

 roughly parallel to the foliation of the granite. Some of the inclu- 

 sions are rather sharply separated from the granite, many of them 

 had their borders assimilated, while still other anorthosite caught 

 up in the granite magma was completely assimilated to form Keene 

 gneiss. 



The interesting lot of rocks on the steep hillside one-half of a 

 mile north-northwest of Bailey pond has been described above under 

 the caption " Keene gneiss." 



A big ledge in the brook at the old road crossing i mile west- 

 northwest of the summit of Hayes mountain shows typical White- 

 face anorthosite closely involved with granite with apparently slight 

 development of Keene gneiss. 



The margins of the small body of Whiteface anorthosite sep- 

 arately mapped on top of Hayes mountain appear to have been 

 assimilated and close to its borders the anorthosite carries quartz 

 (no. 18 of table i). 



The small area of anorthosite and granite mixed rocks on top 

 of Wilson mountain shows numerous little inclusions of Marcy anor- 

 thosite in the granite, these having been described in the above dis- 

 cussion of the anorthosite. The relations are shown in figure 1. 



