ADIRONDACK SYENITE AREAS 187 



wlien weathered, are absolutely not to be distinguished from other rocks 

 of apparently quite different relationships. 



A variation is also shown in the opposite direction. Belts of veiy 

 acid, red granitic gneisses consisting essentiall}^ of microperthite and 

 quartz, with or without hornblende and augite, occur in the S3^enite- 

 gneisses and seem, to grade into theni. For the most part the}^ differ 

 greatly in appearance from the usual granitic gneisses of the Adiron- 

 dacks, being of coarse grain, M'ith the quartz in the mucli elongated form 

 in which it is found in the S3'enite-gneiss. These rocks are not so well 

 shown in the Loon Lake l)elt as in others to be mentioned. The seem- 

 ing gradation of the one into the other, the identity of the hornblende 

 and augite, when they occur, in the two rocks, and the peculiar type of 

 quartz are the reasons for assuming a near relaticmship to one another. 



SALMON niVER 



A smaller belt of sj^enite-gneiss, some 6 miles long and 2 miles broad, 

 runs from a i)oint about 7 miles south of Malone down into Duane town- 

 ship. It is cut through b}' the Salmon river and the rocks well ex- 

 posed, especially at Chasm falls. The fresh green gneisses are quite like 

 those at Loon lake ; but red gneisses make up a more considerable part 

 of the exposures here, and- in part the color is produced b}'' weathering, 

 instead of indicating a more acid rock. As a whole, hornblende is more 

 prominent and p3a'oxenes less so in this belt, but no other differences 

 appear and the identity of the rocks is beyond question. The onl}^ 

 doubt is in regard to their areal extent, as the}^ fade out into other rocks 

 through puzzling intermediate phases. 



According to Smyth the Diana sj'^enite belt is from 15 to 20 miles long 

 and 2 to 4 broad, with very indefinite limits on all sides but the north.* 

 To the south })atches of it appear frequently in the midst of gneiss, into 

 which it seems to blend, although the relation is obscure. Irruptive 

 contacts with the limestones of the Grenville series are well shown, es- 

 pecially at Bonaparte lake. Professor Smyth writes me that he has 

 found no other large area of this rock in the western and southern 

 Adirondacks, though occasional small patches occur, with a wide range 

 in distribution. t 



MOUNT DEFIANCE 



Professor Kemp has called my attention to the probable identity of 



*C. H. Smyth, Jr. : This Bull., vol. vi, pp. •271-'T4. 



t An extended description of the Diana belt will lie fuinul in Fi'ofe.ssor Smyth's forthcoming 

 report in the 17th Ann. Rep, State Geologist of New York, 



