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. 
