

GEOLOGY OF THE WEST POINT QUADRANGLE, NEW YORK 83 



regular structural stock, yet it is perfectly clear that the jointing 

 which has caused the real trouble is natural. 



A mile further east across a stretch of low-covered ground, the 

 Mohegan quarries lie in the same formation. Several openings have 

 been worked at this point, most of them comparatively small, A 

 peculiar color quality is produced here which makes the stone unusu- 

 ally attractive to architects. The Mohegan granite has been used 

 in the Cathedral of St John the Divine of New York City. The 

 principal color is a sort of buff, which is very unusual for a granite, 

 but it seems to be strictly a primary color. 



Both of these quarries are marginal in the granite mass which is 

 genetically related to the Cortlandt series. No other places have 

 been worked in this rock. 



A granite quarry was opened some years ago on the south side 

 of Breakneck mountain and a considerable volume of stone was 

 removed. It was abandoned, however, apparently because of the 

 close jointing and the structural irregularity of the stone. This 

 rock is the Storm King granite type which has a rough gneissoid 

 habit and strong pegmatitic tendency. Both of these tend to make 

 the quarrying of massive blocks difficult. These characteristics do 

 not necessarily interfere with use for rougher purposes than build- 

 ing stone, such as crushed stone or cyclopean masonry or for foun- 

 dations ; but it is doubtless the difficulty of working, especially the 

 tendency to produce irregtilar and curved surfaces in quarrying, 

 rather than its petrographic quality that has discouraged working. 



At many oth.er places small workings may be seen, but most of 

 them have figured only in local use and are so placed that the trans- 

 portation handicap could not be overcome for a wider market. 

 High-grade granites from other sources meet the requirements of 

 the market so fully that it would require extraordinary conditions 

 or particular quality to gain a position of economic importance. 



It is true, however, that granitic rocks both of massive and especi- 

 ally of gneissoid varieties occur in very great abundance in this 

 quadrangle and could be produced in large quantity. Their quality 

 is good enough to meet all normal requirements, but considering all 

 controlling factors it is not likely that large supplies will be drawn 

 from any of this ground for building stone purposes. 



An occasional gneissoid type of rock is found to give rather 

 good architectural effect and it may possibly be that such quality of 

 rock viall be in higher favor in the future. If such a thing should 

 6 



