GEOLOGICAL POSITION AND GEOGRAPHICAL DISTRIBUTION 205 



line rocks whose uses are the same. In fact, the similar adapt- 

 ability and use have brought these latter species into the 

 class of granites. For example, the Au Sable granite of 

 Essex county is a gabbro. The term is applied in some cases 

 to the diabases or trap-rocks, as the ''granite quarries" of 

 Staten Island. Syenite differs from granite in having more 

 hornblende, with some plagioclase feldspar and mica and 

 little or no quartz. It is massive and its occurrence is like 

 that of granite. And the same general statements apply to 

 Its durability as to granite. 



Another massive crystalline rock which is used in building 

 is norite and consisting of labradorite and hypersthene, with 

 some brown mica. It is a common rock In the Adirondack 

 region and Is known 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. Granites, syenites, 

 pegmatites and other massive rocks are found In veins and 

 dikes in the Highlands and in Westchester county; but 

 there are no quarries opened in these out-crops. The so- 

 called granites of the Piudson river quarries are, with the 

 exception of that on Break Neck mountain, granitoid 

 gneisses and syenite gneisses. The schistose class of crys- 

 talline rocks is developed extensively In the Highlands of 

 the Hudson and in the border of the Adirondack res^Ion. 

 On New York island and within the city limits the gneissic 

 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 Yonkers-; at Kensico ; atTarrytown and at Ganung's, 

 west of Croton Falls. In Putnam county there are quarries 

 near Peekskill ; and near Cold Spring. West of the river 

 there are quarries on lona Island ; at West Point ; near 

 Suffern's ; at Ramapo ; on Mt. Eve, near Florida ; and, on 

 Storm King Mt. near Cornwall. The out-crops of these 

 schistose or foliated rocks are so numerous in the belt of 

 the Hudson Highlands that quarries can be opened at many 



