ROGERS, GEOLOGY OF THE CORTLANDT SERIES 73 



Emery Schist Type 



Emery schist is a very common type in the southeastern part of the 



Cortlandt area, in the Dickerson and Salt Hill region. The country had 



here been widely prospected for iron at the time when it was thought 



that the ore was magnetite. The emery has been mined on the roadside, 



at the southeast corner of Salt Hill; and it is said to run more or less 



continuously over the mountain to the north. Here it appears to trend 



more to the east, being mined in several places on the eastern slope of 



Dickerson Hill. This seems to be the chief vein, but there are several 



other outcrops, some of which are. along the border of the district to the 



west and east. 



In all of the outcrops visited by the writer, the ore is of the same type ; 

 a vein of black emery (which in thin section is seen to be the feldspathic 

 variety) is bordered on either side by the quartz emery schist. More 

 often, perhaps, no distinction can be made between the two; the emery 

 merely becomes quartzose in streaks. Bands of pure quartz a foot or 

 more across are not uncommon. The quartz streaks are not always 

 straight; they are often strongly contorted and crumpled. The opening 

 on the road above referred to is within a hundred feet of the border of 

 the series, and possibly less; and so closely does the emery in all but 

 color resemble a coarse schist, that it was difficult to decide on its iden- 

 tity offhand. To the north of this, about a quarter of a mile, is a small 

 inclusion of mica schist, strike 1ST. 20° E. 80° E. ; and 75 yards south of 

 this outcrop, emery is again taken out. The strike of this inclusion is 

 very close to the general strike of the schist in this district and also of 

 the emery schist. The latter varies from N. 35° E. to N. 60° E., but it 

 generally approximates the former. On the west side of Salt Hill, ore 

 was found in a tongue of pyroxenite which seemed to be projecting 

 directly into another inclusion of schist. 



The ore of this type, therefore, is sometimes on the border of the 

 series, near the contact with the mica schist, sometimes near an inclusion 

 of the same in the igneous rocks, while again, although it shows exactly 

 the same structure, no association with schist was observed. 



Norite Type 



ISTorite and the following type are found chiefly in the northeastern 

 area, where all of the larger workings are located; but in this area, the 

 emery is always associated with this peculiar variety of norite, or else as 

 is indicated below under the following type. The succession and rela- 



