ECONOMIC GEOLOGY 



183 



posable varieties of pyrite is mot only prejudicial to strength 

 and durability but also to the beauty of the stone as soon as it 

 begins to decay. 



The term ' granite ' as used among builders and architects is 

 not restricted to rock species of this name in geologic nomencla- 

 ture, but includes what are known as gneisses (foliated and 

 bedded granites), diorites, gabbro and other crystalline rocks 

 whose uses are the same. In fact, the similar adaptability and 

 use have brought the latter species into the class of granites. 

 For example, the Au Sable granite of Essex county is a norite. 

 The term is applied in some cases to the diabases or trap-rocks, 

 as the ' granite quarries ' of Staten Island. 



Another massive crystalline rock which is used in building is 

 norite, consisting of labradorite and hypersthene, with some 

 brown mica. It is a common rock in the Adirondack region, and 

 is known commercially as a granite. 



The massive crystalline rocks are of common occurrence in 

 New York, but not in ■outcrops over extensive areas, excepting 

 in the Adirondack region and in the Highlands of the Hudson. 

 The schistose crystalline rocks are developed extensively in the 

 Highlands of the Hudson and on the borders of the Adirondack 

 region. On New York island and within the city limits the 

 gneiss rocks have been quarried at many points. In Westchester 

 county there are belts of gneiss and mica schist, in which quarries 

 have been opened near Hastings; near Hartsdale, east of Yonk- 

 ers; at Kensico; at Tarrytown and at Ganung's, west of Croton 

 Falls. In Putnam county there are quarries of granite near 

 Peekskill, Garrison's and Cold Spring. West of the Hudson 

 river there are quarries on Iona island; at West Point; on Storm 

 King mountain, near Cornwall; near Suffern; at Ramapo; and 

 on Mount Eve, near Florida. The outcrops of the gneissoid and 

 granitoid rocks are so numerous in the belt of the Hudson High- 

 lands that quarries can be opened at many points. The supply 

 of stone is inexhaustible. On the Hudson river, between Peeks- 

 kill and Fishkill, there is a fine section of these rocks exposed. 



