THE MINING AND QUARRY INDUSTRY KJI4 77 



but the main ingredients are plagioclase, feldspar and pyroxene, 

 with more or less of amphibole, olivine, magnetite and sometimes 

 biotite. The texture is characteristic, for the feldspar forms lath- 

 shaped crystals which interlace and inclose the pyroxene and other 

 ingredients in the meshes, and it is this firmly knit fabrie which 

 gives the stone the qualities of strength and toughness. 



The largest occurrence of trap in New York is represented by 

 the Palisades of the Hudson and the continuation of the same in- 

 trusion which extends southward through New Jersey onto Staten 

 Island and is also encountered in the interior of Rockland county. 

 The Palisades are the exposed edge of a sill or sheet of diabase 

 that is intruded between shales and sandstones of Triassic age. 

 The sheet is several hundred feet thick, in places nearly iooo feet, 

 and in general seems to follow the bedding planes of the sedi- 

 mentary strata which dip to the west and northwest at an angle of 

 from 5 to 1 5 . The outcrop is narrow, seldom over a mile, and 

 in places is limited to a single steep escarpment. The principal 

 quarries are near Nyack and Haverstraw at the base of the cliffs. 

 Other quarries have been opened near Suffern, Rockland county, 

 on an isolated intrusion, and also near Port Richmond, Staten 

 Island, at the southern end of the Palisades sill. 



Trap occurs in numerous places in the Adirondack's, but mostly 

 as narrow dikes. It is especially common in Essex and Clinton 

 counties where there are many thousands of dikes that range from 

 a few inches to 20 or 30 feet thick. On the southern border of the 

 region are a few dikes of notable size, such as that in the town of 

 Greenfield, Saratoga county, and at Little Falls in the Mohawk 

 valley. A quarry has been opened in the Greenfield occurrence for 

 the supply of crushed stone. 



The quarrying of trap along the face of the Palisades in Rockland 

 county probably will soon be discontinued, as it is designed to pur- 

 chase the quarry properties for the Palisades Interstate Park. The 

 lands to be included within the park extend from the river line to 

 the top of the Palisades. So far only the quarry of the Manhattan 

 Trap Rock Co. has been taken over and closed, but negotiations 

 are proceeding for the acquirement of the other quarries along the 

 river front. 



The future of the industry in this section is somewhat unsettled. 

 It is not unlikely that new quarries may be opened on top of the 

 ridge and in the interior of Rockland county, though the facilities 

 for production and shipment in that section can scarcely be equal to 

 those of the present localities. 



