GEOLOGY OF THE WEST POINT QUADRANGLE, NEW YORK 85 



3 Analysis made by Edison Company (1908) ; furnished by Calvin Tomp- 

 kins of the Tompkins Cove Stone Co. : 



Carb. of Lime 540o 



Carb. of Magnesia 36.00 



Silica 6 . 00 



Oxide Iron and Alumina 4.00 



4 Analysis made 'by A. A. Brennan, 97 Water St., New York (1919) ; fur- 

 nished by Calvin Tompkins of the Tompkins Cove Stone Co. : 



Two samples of limestone were determined for magnesium cai^bonate content 



No. 6223 (blue) 27 . 67%^ Magnesium carbonate 



No. 6224 (grayish white) 30.71% Magnesium carbonate 



A continuation of this same formation may be traced along Peeks- 

 kill hollow for several miles, but it is everywhere covered rather 

 heavily with drift and does not stand favorably for exploitation. 

 This condition is somewhat better as one traces the beds to the 

 northeast, but transportation becomes more difficult and the prospect 

 of competing successfully with the other limestone quarries situated 

 on the Hudson river is questionable. 



On the opposite side of the river from Tompkins cove, at Ver- 

 planck point, there are other quarries also in limestone, which have 

 been extensively worked. They are quite as favorably located as 

 those at Tompkins cove, but have not been developed so system- 

 atically and the character of the stone is somewhat different, in that 

 metamorphism in the direction of strong, rather coarse recrystalli- 

 zation is much more pronounced. This affects the quality of the 

 stone to some degree, and it is therefore placed at a disadvantage 

 since the fine-grained varieties are preferred. There is a large avail- 

 able supply here, however, and certain beds are undoubtedly service- 

 able. 



Crystalline limestone of Inwood type occurs in the southeast 

 corner of the quadrangle between Yorktown Heights and Amawalk. 

 The rock is a true marble in its crystalline habit and certain beds 

 are quite as good as the Tuckahoe marble. The rock is, however, 

 rather coarse and soon shows the effect of the weather. On this 

 account the Inwood type of stone has little market. Although it 

 would be possible to produce any quantity of this stone from this 

 and adjacent areas farther to the south it is not likely that large 

 development will be undertaken chiefly because of the short life of 

 the stone. 



A quarry was at one time worked in the Sprout Brook limestone, 

 which is an jnterbedded Grenville limestone. It is an exceedingly 

 complexly metamorphosed rock with much deformation and igneous 



