THE MINING AND QUARRY INDUSTRY I37 



Niagaran group. The next group of limestones in ascending 

 order is the Niagaran, which comprises the Lockport and Guelph 

 formations. The latter is a typical dolomite, fine grained and of 

 grayish color. It occupies a limited area in Monroe and Orleans 

 counties, and is quarried near Rochester. It has been used for 

 lime. The lower member of the group, the Lockport dolomite, out- 

 crops in a continuous belt several miles wide from Niagara Falls 

 east to Onondaga county, and then with diminishing width across 

 Madison county. Like the Guelph it contains magnesia, and this 

 component may be present in sufficient quantity to make it a dolo- 

 mite. The lower part is usually silicious, grading into shale. The 

 upper portion which is heavy bedded is adapted for building mate- 

 rial, road metal, lime, etc. There are quarries around Niagara 

 Falls and Lockport. It is also worked at Rochester and to some 

 extent in Wayne, Onondaga and Madison counties. 



Cayugan group. The Cayugan group with its members is note- 

 worthy economically, as it contains the valuable gypsum and salt 

 deposits besides the hydraulic limestones that are utilized for cement. 

 The basal strata, comprising the Salina stage, are mostly shales, 

 though thev interbedded with thin layers of dolomitic limestones. 

 In the Cobleskill, Rondout and Manlius stages, limestones prevail. 

 In the Rosendale district of Ulster county they have furnished large 

 quantities of material for the manufacture of natural rock cement, 

 and they are the source of the cement rock in Onondaga and Scho- 

 harie counties. The purer limestones of the group are employed 

 in Onondaga county for lime making. 



Helderbergian group. At the base of the Devonic system, the 

 Helderbergian group is prominent for its limestones. The latter 

 are strongly developed along the Hudson- river in Albany, Columbia, 

 Greene and Ulster counties. The Coeymans or Lower Pentamerus 

 formation affords rock suitable for lime, building stone and road 

 material, while the Becraft or Upper Pentamerus is employed as 

 an ingredient of Portland cement and for furnace flux. There are 

 quarries at Hudson, Rondout, South Bethlehem and Catskill. 



Onondaga limestone. Of the remaining formations represented 

 in New York, the Onondaga is the only one that is of much import- 

 ance for limestone quarries. It outcrops in Orange, Ulster, Greene 

 and Albany counties, and is exposed quite continuously through the 

 middle and western part of the State. Building stone and lime 

 are the principal products. Quarries have been opened at Kingston, 

 Split Rock (near Syracuse), Auburn, Waterloo, Seneca Falls, 

 Leroy, Buflfalo, and many other places. 



