1 88 NEW YORK STATE MUSEUM 



blende or biotite or both. It is gray to pink when fresh and 

 weathers Hght brown. The granite porphyry is biotitic to some- 

 times hornblendic with large feldspar crystals embedded in a fine 

 to medium-grained matrix. It is gray to pinkish gray when fresh 

 and weathers brown. These igneous rocks are important because 

 they almost invariably constitute the mountain masses of the region. 

 All of these rocks show a distinct gneissoid structure, but are 

 usually very homogeneous in large masses. 



Minor intrusions, cutting all of the above masses, occur as dikes 

 of gabbro, pegmatite, and diabase but these have no bearing upon 

 the present discussion. 



An important structural feature is the presence of numerous nor- 

 mal faults which have greatly dissected the region. 



Finally it should be stated that this portion of the Adirondacks 

 has been vigorously glaciated. 



LOCATION AND DESCRIPTION OF TYPICAL DOMES 



Since these domelike, topographic forms are so numerous and 

 characteristic of the region, a few only of the more pronounced 

 and easily accessible ones will be mentioned, as follows : Potash 

 mountain, 4 miles north of Luzerne; the Three Sisters, including 

 Pine and Bald mountains on the Luzerne sheet and 3}^ miles south- 

 west of Warrensburg; Hackensack mountain at Warrensburg; 

 Kelm, Moon, and Potter mountains respectively 3^ miles north, 

 3 miles northwest, and 4 miles west-northwest of Warrensburg; 

 Prospect mountain at Chestertown ; Mill and Stockton mountains 

 (not named on map) respectively lYi and 2 miles east of Johns- 

 burg; and Huckleberry and Crane mountains, respectively 3^ and 

 5 miles south of Johnsburg. 



Potash mountain is a remarkable topographic form which is 

 known for miles around as the " Potash Kettle " and it is doubtful 

 if there is a finer example of an exfoliation dome in New York 

 State. The accompanying photograph gives but a poor idea of this 

 steep, domelike mass because it fails to show it in its landscape 

 setting. From base to summit, on the west side, the mountain rises 

 1 100 feet very abruptly and it attains an elevation of nearly 1800 

 feet above sea level. It presents a striking view toward the east 

 from the train window, between Luzerne and Stony Creek. 



The Three Sisters form an interesting group of sharp pointed 

 domes which reach altitudes of 2000 to 2100 feet above the sea or 



