90 NEW YORK STATE MUSEUM 



for exploratory purposes in connection with the Catskill aqueduct 

 investigations, encountered a water-bearing zone in the crushed 

 gneisses or granites along a fauh, and a flowing well was thus 

 developed. This furnished the basis for an extra damage claim in 

 connection with the condemnation proceedings and the nature of 

 that claim is described in connection with engineering problems on 

 a later page. The quality of the waier is good but nothing extraor- 

 dinary for such a region. Doubtless similar quality can be obtained 

 elsewhere at numerous places, but it would not be easy to discover 

 another combination of circumstances which would be certain to 

 produce a flowing well. 



Emery. The Cortlandt area near Peekskill is one of the very few 

 places in America from which emery is produced. These deposits 

 occur in the norites of the Cortlandt series as rather limited local 

 developments. They exhibit very unusual mineral association, 

 among which are magnetite, corundum, spinel and epidote in addi- 

 tion to or instead of the usual minerals of the norite series. These 

 patches usually have a distinctly banded structure which is normally 

 lacking in the norites themselves and which suggests the existence of 

 some older rock which has been in large part destroyed, but whose 

 structure is in part preserved. They probably represent xenolithic 

 masses which have been able to attract from the magmas in which 

 they were immersed or have at least helped to fix certain constituents 

 which together with those already in the rock have given the abnormal 

 minerals of the emery deposits. 



This origin was suggested by the senior author some years ago 

 during his study of the Tarrytown quadrangle and the detail has been 

 worked out in a petrographic study by G. S. Rogers,^® whose dis- 

 sertation on the Cortlandt series furnishes the best description of 

 this area. The following items bearing on the emery deposits them- 

 selves have been extracted from his paper. Description of the form- 

 ation is given in a different section. 



" The abrasive, emery, is an intergrowth of magnetite and corun- 

 dum. It occurs in veins and pockets with occasional well-developed 

 lenses. The types are spinel emery, pure emery, feldspathic and 

 quartz emery schist, associated with norite and sillimanite schist." 



Rogers summarizes his description as follows : 



" I The ore usually occurs in a region in which mica schist inclu- 

 sions are abundant and often within a hundred feet or so of such an 

 inclusion, and the largest (McCoy. Dalton etc.) are within looo feet 

 of the border of the Cortlandt series. 



''Rogers, G. S., N. Y. Acad. Sci., Annals, 21:11-86 (1911). 



