24 NEW YORK STATE MUSEUM 



acidic variation of the normal syenite. Examples of such variations 

 are given above in the discussion of the granitic syenite. Also, in 

 another direction, there is a transition to the granite porphyry be- 

 low described. 



Texturally and structurally the granites show practically the same 

 variations as the normal syenite and no restatement of these is here 

 necessary. The pinkish-gray color is usually not a mere surface 

 weathering effect, but pervades the whole rock body and appears to 

 be due to stains and specks of hematite. In the table on page 26 

 the mineralogical compositions of selected examples are given. 

 Compared with the normal syenite there are to be noted especially 

 the frequent occurrence of considerable microcline ; higher quartz 

 content ; the lesser prominence of hornblende ; and the greater 

 prominence of biotite. 



Included streaks or bands of Grenville or amphibolite are more 

 common in this pink granite than in any of the other rocks, though 

 these by no means always occur. Some considerable areas of rather 

 homogeneous granite are practically free from inclusions. For 

 example, almost continuous ledges of very typical reddish, biotite 

 granite gneiss, along the creek from i to 2 miles east of Alvord 

 P. O., are almost wholly devoid of inclusions. 



Along the creek from one-fourth to one-half of a mile below 

 Dunning pond, there are big ledges of variable granitic syenite to 

 red granite so full of gray Grenville gneiss inclusions as to make 

 up a considerable percentage of the rock. Usually these inclusions 

 are drawn out parallel to the foliation, though sometimes they are 

 twisted into various positions and frequently they pinch out sud- 

 denly. There appear to be all stages from thoroughly fused in 

 Grenville to some which has been but little affected. At one place 

 syenitic-looking rock was seen in the same ledge with granite and 

 the syenite seems to have been produced by assimilation of Gren- 

 ville by the syenite magma. 



A very fine display of the red to gray granite with numerous in- 

 clusions may be seen in the big ledges in the bed of Hamilton Lake 

 stream one-half of a mile below the mouth of Gallup creek. Much 

 of this rock is distinctly banded due to alternating layers (up to 

 3 feet wide) of reddish granite and amphibolite, the latter being 

 inclusions drawn out parallel to the very distinct foliation of the 

 granite. At times the whole shows a considerable twisted or con- 

 torted structure. These ledges look more like the so-called 

 " Laurentian " granite of the Thousand Islands region than any 

 others seen within the quadrangle. 



