ECONOMIC GEOLOGY 189 



Oneida conglomerate 



This formation is developed to its greatest thickness in the 

 Shawangunk mountain in Orange and Ulster counties. 



It is recognized in the Bellevale and Skunnemunk mountains, 

 also, in Orange county. In the central part of the state it is 

 traced westward in a narrow belt from Herkimer county into 

 Oneida county. The prevailing rocks are gray and reddish-gray, 

 silicious conglomerates and sandstones, which are noted for their 

 hardness and durability. The cementing material is silicious. 

 The jagged edges and angular blocks and the polished and 

 grooved surfaces of the glaciated ledges, so common on the 

 Shawangunk range, afford the best proof of the durable nature 

 of these rocks. The bottom beds, near the slate, contain some 

 pyrite. No attempt has been made to open quarries for stone, 

 excepting at a few localities for occasional use in common wall 

 work. The grit rock is quarried near Esopus creek for mill- 

 stones, and at Ellenville is crushed for glass sand. 



The accessibility of the outcrops to the New York, Lake Erie 

 and Western railroad, the New York, Ontario and Western rail- 

 road, the West Shore railroad and the Delaware and Hudson 

 canal lines is an advantage, as well as the comparative nearness 

 to New York. No other formation in the state exhibits in its 

 outcrops better evidence of ability to resist the weather. 



Medina sandstone 



The Medina sandstone is next above the Oneida conglomerate. 

 It is recognized in, the red and gray sandstones and the red and 

 mottled (red and green) shales of the Shawangunk and Skunne- 

 munk mountains in Orange county. A large amount of the red 

 sandstone has been quarried on the north end of the Skunne- 

 munk range, in the town of Cornwall, for bridge work on the 

 railroads which cross the range near the quarry. 



The red sandstone is seen exposed in the cuts of the Erie 

 railway northeast of Port Jervis. This formation reappears in 

 Oswego county, and thence west to the Niagara river in a belt 

 bordering Lake Ontario. 



