Geographical Distribution. 13 



2. TRAP-ROCK. 



Trap-rock is the common name given to a certain class of eruptive 

 or igneous rocks, which are unstratified. They are made up of a 

 feldspar (usually labradorite) and augite, with some magnetite and 

 titanic iron. The mass is generally of a dark color and finer-grained 

 than the granites. The rock of the Palisades opposite New York city 

 is an example. In New York these trap-rocks make up the Pali- 

 sade mountain range and the Tome mountain, on the west side of 

 the Hudson river from the New Jersey line to Haverstraw. There is 

 an outcrop on Staten Island also, where the rock was quarried under 

 the name of granite. The only place where the stone is steadily 

 worked is on the river bluff at Rockland Lake. 



The existence of unstratified rocks of this group in the Adirondack 

 region is known, but of their extent and localities there is much un- 

 certainty. Their importance as a source of material for constructive 

 uses is inconsiderable where there is so much granite, gneiss and other 

 stone which are worked more economically and dressed more readily. 



3. MARBLES. 



Marble has been defined to be " limestone which has a granular 

 texture." But as already noted, the term is used in New York State 

 to apply to any calcareous rock which takes a fine polish and may be 

 used as an ornamental or decorative material. In this report the 

 term is restricted to the crystalline limestones, whether massive or 

 unstratified, or metamorphosed or altered sediments. The texture 

 and not the use is the basis of the distinction between ordinary lime- 

 stones, which are not crystalline, and the marbles. Crystalline 

 limestone is a common rock in Westchester, Putnam and in the 

 eastern part of Dutchess counties. There are small outcrops in 

 Orange county also. The Adirondack region has its belts of the 

 same rock. And, in general the territory of the granites, gneisses 

 and syenites contains here and there patches of crystalline limestone, 

 and also possible sources of marble. Marble has been quarried at 

 King's Bridge and Tremont in New York city : at Tuckahoe, Scars- 

 dale and Pleasantville near the Harlem railroad line ; at Hastings, 

 Sparta and Sing Sing on the Hudson river ; and at South Dover and 

 Dover Plains in the eastern part of Dutchess county. In the Cham- 

 plain valley there is a quarry at Port Henry. On the north-west 

 side of the Adirondacks there are large quarries at Gouverneur. 



