GEOLOGICAL POSITION 



AND- 



Geographical Distribution of Building Stone 



ZUST ZTnTIEW tore. 



The crystalline rocks are limited in the outcrops to the Adirondack 

 region, the Highlands of the Hudson,* Westchester and New York 

 counties, the Rockland county trap range, Staten Island and a very 

 small area on Long Island. The Hudson- Champlain valley, a part 

 of the St. Lawrence valley and the central, southern-central and 

 western parts of the State have sandstones and limestones as native 

 building stone. 



The geological horizon, the occurrence, the localities and general 

 notes on the building stone of the several subdivisions or groups are 

 given here under their respective heads. 



I.-CEYSTALLINE BOOKS. 



1. GRANITES, SYENITES, GNEISSES, MICA SCHIST. 



Granite, in its proper signification, is a crystalline rock, consisting 

 of feldspar, quartz and mica. These constituents are aggregated 

 together in an intimate mixture and in varying proportions. The 

 minerals may be of larger or smaller size, from the scarcely discern- 

 ible grains or crystals to masses an inch or more in length ; and 

 hence the stone is said to be coarse-grained or fine-grained, or coarse 

 crystalline and fine-crystalline. But the typical granite is not the 

 more common form or ^variety. Besides the essential, constituent 

 minerals, there are hornblende, pyroxene, epidote, garnet, tourma- 

 line, magnetite, pyrite, chlorite, graphite, any of which may come in 

 as accessory minerals. Generally some one of these minerals is present 



* The crystalline rocks of eastern Dutchess county and a part of Columbia are in- 

 cluded in the Highlands. 



