132 NEW YORK ■ STATE MUSEUM 



situated along the highway, just north of Larchmont station. As 

 the vicinity is now a residential section, it is doubtful if work will 

 again be started. 



The diorite is here massive or slightly foliated, and of lighter color 

 than the average. It shows efifects of weathering in iron discolora- 

 tion and clouding of feldspars. Pegmatitic segregations of the 

 constituents are noticeable in places. The foliation strikes northeast 

 and dips about 55° northwest, conforming to which is the principal 

 joint system. 



The product of the quarry is stated to have been about 1000 cubic 

 yards a year, mostly dressed stone. 



A quarry, owner unknown, is situated in the interval between the 

 Campbell and Faillace quarries, southwest of Mamaroneck. It 

 was not in operation in the spring of 1913, and apparently had been 

 abandoned for several years. It shows a face 100 feet long on the 

 strike of the diorite and from 20 to 35 feet high, with a width of 

 50 feet. The structural features resemble those at the Faillace 

 quarry. The rock is a dark gneissoid type, quite uniform as to 

 composition and appearance. Pegmatite in small segregations and 

 stringers is the only variation at all noticeable. There is no equip- 

 ment on the property. The product seems to have been mainly 

 dimension stone. 



THE FORDHAM BANDED GNEISS 



The Fordham gneiss is a variable rock, or rather an assemblage 

 of more or less contrasting types, which spread over an extensive 

 area on the east side of the Hudson. It occurs in several belts that 

 follow the general northeasterly structural trend and that have the 

 Harlem river as their approximate southern boundary. In southern 

 Westchester county, it borders the Yonkers on both sides, and a 

 small strip continues along the eastern edge of the main Yonkers 

 area to its northern end. Another belt is exposed along the Hudson 

 from the Harlem river northward, occupying most of the first line 

 of ridges that parallel the river. 



The Fordham is a banded gneiss, in which respect it differs from 

 the Yonkers. This banding is caused by variation in mineral com- 

 position, the lighter bands having less biotite than the darker ones. 

 Some light bands are made up of nearly pure quartz, but usually 

 there is a large proportion of feldspar. In the main, the rock may 

 be classified as a biotite gneiss, composed of quartz, feldspar and 

 biotite in fluctuating amounts. The feldspars are orthoclase, micro- 

 cline and an acid plagioclase, the latter having the characteristics 

 usually of oligoclase. The color is grayish and averages darker 



