84 NEW YORK STATE MUSEUM 



happen it would be difficult to find a more promising field of develop- 

 ment than the gneissoid granites of the Highlands of New York. 



Limestone and marble. A very high-grade, finely cr3'stalline 

 limestone occurs at Tompkins cove, follovvang the margin of the 

 down-faulted block at that point, and extends from the river south- 

 westward to the limit of the quadrangle. The beds stand at a high 

 angle and are associated with a phyllite in similar manner to the 

 association of these two rocks along Peekskill creek. They are 

 judged, therefore, to belong to the Hudson River- Wappinger series 

 and the Tompkins Cove limestone is accordingly correlated with 

 the Wappinger. Beds vary greatly in quality, some of them being 

 highly siliceous and certain beds more strongly magnesian than 

 others. 



The density of the stone, however, and its large development, 

 together with its excellent location for cheap transportation as well 

 as other favorable conditions at this locality have made the working 

 of this stone a very large and prosperous undertaking. The stone 

 is as good quality as can be produced from limestone. It is used 

 very extensively for ordinary crushed stone purposes and the market 

 in New York and vicinity, where it supplements the trap rock 

 and other crushed stone demands for various structural purposes, 

 absorbs the total production. 



The rock is rather strongly metamorphosed and has developed 

 silicates to some degree from its original impurities, but this trans- 

 formation has not made it coarse and granular and weak to the 

 degree attained by some of the other limestones, notably the Tnwood. 



The following analyses represent the chemical quality of the 

 stone : 



1 Analysis recorded in New York State Aluseum, 51st Annual Report, 

 2:450 (1897) ; also in Bui. 44, p. 438 (1911) : 



Si02 12 . 00 



AI2O3 413 



FejOs 1 .05 



CaC03 23 .34 



MgCOa 16 . 74 



CO2 39- 1 



2 Analysis made by Richard K. Meade, Baltimore, Md. (1919) ; furnished 

 by Calvin Tompkins of the Tompkins Cove Stone Co. : 



Silica 8. 10 



Iron oxide and Alumina i . 24 



Carb. of Lime 54- So 



Carb. Magnesia 36 . 36 



