68 NEW YORK STATE MUSEUM 



fresh material at the surface. There are scattered inclusions of 

 dark hornblende and biotite gneiss, probably the Fordham, but with 

 this exception it is quite free of admixture and well adapted for 

 building and general construction purposes. Its composition is 

 that of a normal biotite granite. The gneissoid character is partly 

 at least original, rather than assumed after the crystallization, and 

 the texture is firmly knit like that of a massive rock. The effects 

 of shearing and compression are observable, however, in restricted 

 areas. The granite is quarried by drilling and blasting. The heavier 

 blocks are used for cyclopean masonry, and the smaller material 

 goes to the crushing plant, which is a large concrete and steel 

 structure. 



Mamaroneck. Quarry operations are conducted by Faillace 

 Brothers in an exposure of grano-diorite in the town of Mamar- 

 oneck, a little west of the village of that name. The rock belongs 

 to the large intrusion which extends northeasterly across Rye and 

 Harrison townships into Connecticut where it is known as the Dan- 

 bury grano-diorite. It is medium to dark in color, with abundant 

 biotite which by its linear arrangement lends a gneissoid appear- 

 ance to the mass. It has a fine grain, varied at times by porphyritic 

 feldspars which measure up to an inch in length. The porphyritic 

 phase resembles very much the augen-gneiss at Bedford in northern 

 Westchester county. 



The Faillace quarry consists of an opening along a northeast- 

 southwest ridge, 200 feet in length and 30 to 50 feet in height. 

 The grano-diorite is here rather dark, rich in biotite, and carries 

 considerable garnet. It shows traces of sheet structure as exposed 

 in the quarry, the sheets being from 6 to 8 feet thick and dipping 

 slightly southward. The principal set of joints strikes northeasterly 

 parallel to the foliation and dips 75 ° or so northwest. Another 

 system crosses this at a high angle but is irregular and at times 

 obscure. The rock is quite uniform in appearance, being fairly 

 free of knots and streaks and pegmatitic injections. The color 

 effect of the cut stone varies somewhat on the different sides. 

 Parallel to the foliation the biotite is more in evidence than the 

 feldspar and lends a very dark, almost black, color to that side. 

 Across the foliation, the color is grayish, mottled by the white feld- 

 spar augen, which are more prominent in the horizontal plane. 

 For building purposes, it is cut so as to present the lighter color, 

 across the foliation. 



