22 NEW YORK STATE MUSEUM 



21 is a good pink granite. These types grade back and forth into 

 each other several times in this one outcrop. There are many 

 narrow streaks, layers, or inclusions of Grenville dark, biotite- 

 feldspar-quartz gneiss sometimes containing garnets. At times 

 these streaks are rather clearly defined, while again they are not, 

 but always, though often locally twisted, they roughly follow the 

 gneissic bands. The texture and homogeneity, especially of the 

 granite, vary considerably and a few garnets occur sporadically in 

 the syenitic and granitic facies. The ledge is perfectly bare with 

 relationships well shown, and it seems certain that the dark (dioritic) 

 streaks are Grenville which have been more or less fused into the 

 molten granite. Where thoroughly assimilated, the basic rocks have 

 resulted, and where not thoroughly fused in the streaks are still 

 visible. Every stage of the assimilation process is shown. 



Another locality where the relationships between syenite, granitic 

 syenite, and Grenville are very clearly exhibited on a much larger 

 scale is in the vicinity of the top of Mount Francisco. Begin- 

 ning one-quarter of a mile northeast of the mountain top and pass- 

 ing one-half of a mile southwestward across the mountain top, one 

 may observe the gradation from basic syenite, through normal and 

 granitic syenite to pinkish granite. The mountain top has been 

 burned over, thus exposing a great bare rock ledge in which the 

 normal syenite (no. 27 of table on page 16) grades perfectly into 

 granitic syenite (no. 2yh of the table), and this into typical granite 

 (no. 34a of the table on page 26) . . There is no possibility that one of 

 these rocks cuts another. The basic syenite (no. 12 of table on page 

 16) also almost certainly grades into the normal syenite. From the 

 basic syenite to the granite there is a progressive diminution of the 

 dark-colored minerals from 19 to y/2 per cent. From the normal 

 syenite to the granite no streaks or inclusions of Grenville were 

 noted so we here seem to be dealing with a case of simple differ- 

 entiation. 



At many other places, especially wnthin the large granitic syenite 

 area between Whitehouse and Hamilton mountain, there are more 

 or less intimate relations of syenite, granitic syenite, and granite. 

 Thus just east of Buck pond the granitic syenite contains a layer 

 (several feet wide) of pink granite and it is not a dike. From 

 this point southwestward for one-half of a mile, there are shown 

 by rapid gradations all sorts of rocks from hornblende syenite and 

 granite to almost granite porphyry. Such rocks play back and 

 forth upon each other repeatedly. 



