136 . NEW YORK STATE MUSEUM 



and in southeastern New York it has been metamorphosed and has 

 the crystalHne character of marble. The noncrystaUine Hmestones, 

 to which the present discussion is Hmited, are associated with the 

 Lower Siluric, Upper Siluric, and Devonic systems. Those chiefly 

 exploited will be briefly described. 



Beekmantown limestone. The Beekmantown limestone or cal- 

 ciferous sandrock, as it has been commonly called, occurs in isolated 

 areas along the Mohawk and Champlain valleys. There are quarries 

 in Warren, Montgomery, Fulton and Herkimer counties. It is a 

 fine grained, massive stone of grayish color and normally contains 

 more or less magnesia. This constituent sometimes occurs in suffi- 

 cient amount to characterize the rock as dolomite. Owing to its 

 prevailing silicious nature, the limestone can seldom be used for 

 other than building purposes. 



Chazy limestone. The Chazy limestone is of local importance. 

 It is found along a narrow belt bordering the Adirondacks from 

 Saratoga county north to Clinton county. It attains its greatest 

 development in the eastern and northern parts of Clinton county. 

 In composition it is a typical limestone, containing little magnesia 

 or impurities. For this reason it is adapted to the manufacture of 

 lime. The stone has a finely crystalline texture, and at Chazy and 

 Plattsburg has been quarried for marble. It supplies also some 

 building stone and furnace flux. 



Trenton group. In the Mohawkian or Trenton group are in- 

 cluded the Lowville (Birdseye), Black River and Trenton lime- 

 stones, which occupy a large area and possess considerable economic 

 value. They occur in the Champlain valley, but mostly on the 

 Vermont side, and on the southern and western borders of the Adir- 

 ondacks. From the Mohawk valley at Little Falls they form a belt 

 that extends northwesterly with gradually increasing width to the 

 St Lawrence river. The area on the eastern side of Lake Champlain 

 is continued southward into Washington county. The limestone 

 varies somewhat in character according to locality and geologic 

 position. It is often highly fossiliferous. The lower part of the 

 group or Lowville formation is a heavy bedded limestone, but the 

 upper beds commonly contain more or less shale. The color ranges 

 from light gray to almost black. It sometimes shows incipient meta- 

 morphism and has a crystalline texture. The Trenton limestones 

 are quarried in Clinton, Washington, Montgomery, Fulton, Herki- 

 mer, Oneida, Lewis and Jefferson counties. The product is used 

 for building and road material and common masonry. A part is 

 also burned into lime. At Glens Falls, Trenton limestone is em- 

 ployed for the manufacture of Portland cement. 



