﻿I96 NEW YORK STATE MUSEUM 



times the blending with the original metamorphosed Fordham gneiss 

 is so intimate that absolutely sharp limits can not be drawn. And 

 this last condition may well be designated as a third case (c). 



The quarries visited represent all three of these cases. Dinnan, 

 Ferris and Outlet quarries represent essentially the " Yonkers 

 gneiss " type (a) of granite gneiss. Garden quarry represents 

 chiefly (b) the dioritic type of gneiss. City and Smith quarries 

 represent the last case (c), or the mixed and variable type. 



Field character 



City quarry. In accord with the above differences in type it 

 is found that large quantities of uniform material for such purpose 

 as is proposed can not be obtained from City quarry. The rock 

 there is badly jointed and is variable to a marked degree. It was 

 not thought promising enough to test in detail. 



Smith quarry. The conditions of Smith quarry are better but 

 there are similar objections. The amount of uniform material is 

 greater. It would no doubt furnish an abundance of material suit- 

 able for use in the construction of the dam interior, but is not at 

 this point as good a source of facing stone as some of the others 

 to be considered. 



Outlet quarry. Although this rock is characteristic Yonkers 

 gneiss, it has at this place suffered by weathering a peculiar dis- 

 coloration to such extent as to make it objectionable, both from the 

 standpoint of appearance and perhaps of durability. 



Garden quarry. There is an abundance of stone at the Garden 

 quarry. It is fairly uniform. It is no doubt good enough from 

 every standpoint of durability. It is well located. It can be quar- 

 ried readily. But it has a very dark color and is undoubtedly less 

 attractive than a light stone for this .purpose. There are no objec- 

 tionable structures, except where the strong schistose character is 

 developed, and these could be avoided so that with a little selection 

 a fairly uniform stone could be secured. 



Dinnan quarry. This rock is typical ' Yonkers gneiss." 

 There is sufficiently large quantity. It is of good quality. It is 

 situated a little over 2 miles from the proposed dam, but is of easy 

 access. The jointing and other structures do not seem to be objec- 

 tionable. It will work somewhat more easily than a true granite 

 because of the gneissic structure and it has a good medium light 

 color. The discolorations do not seem to penetrate deep and the 

 rock shows only slight decay. 



