62 NEW YORK STATE MUSEUM 



the latter area a belt extends southwest across northern Washing- 

 ton county to Glens Falls in Warren county and is continued into. 

 Saratoga county. Another belt begins in the Mohawk valley near 

 Little Falls and extends northwesterly with gradually increasing 

 width across Oneida, Lewis and Jefferson counties to the St Law- 

 rence river. There are isolated areas of Trenton limestone in the 

 Hudson valley south of Albany. The limestones vary in composi- 

 tion and physical character according to locality and geologic po- 

 sition. They are often highly fossiliferous. In the northern sec- 

 tion they are mostly gray to nearly black in color, contain little 

 magnesia and run as high as 97 or 98 per cent calcium carbonate. 

 The lower part of the group is heavily bedded and well adapted for 

 building stone ; the upper beds commonly contain more or less shale. 

 They are used for various purposes including building and orna- 

 mental stone, crushed stone, lime, portland cement and flux. In 

 the Champlain valley quarries are found near Plattsburg, Lara- 

 bee's Point and Crown Point ; in Washington county at Smith's 

 Basin; in Warren county at Glens Falls where there are extensive 

 quarries that supply material for building purposes, portland cement 

 and lime. The well-known black marble from Glens Falls is taken 

 from the Trenton. Numerous quarries have been opened in Herk- 

 imer, Oneida, Lewis and Jefferson counties. The output of the 

 last named county is specially important, including limestone for 

 building and road construction and lime for manufacture of cal- 

 cium carbide. The principal quarries in Jefferson county are at 

 Chaumont. 



The next assemblage of limestones in the order of stratigraphic 

 occurrence includes the Clinton, Lockport and Guelph members of 

 the Niagara group. The Clinton limestone has a variable impor- 

 tance in the belt of Clinton strata that extends from Otsego county 

 a little south of the Mohawk river across the central and western 

 parts of the State on the line of Oneida lake and Ro hester to the 

 Niagara river. East of Rochester the limestone is relatively thin, 

 usually shaly and split up into several layers, but on the west end in 

 Niagara county it becomes the predominant member and has a more 

 uniform character. Large quarries have been opened recently at 

 Pekin, Niagara county, for the supply of flux to the blast furnaces 

 of the Lackawanna Steel Co., at Buffalo. The upper beds of bluish 

 gray fossiliferous limestone from 10 to 12 feet thick are the purest 

 and analyze from 90 to 95 per cent, calcium carbonate. The Lock- 

 port is a magnesian limestone, in places a typical dolomite, and is 

 rather siliceous in the lower part. It outcrops in a continuous belt, 



