68 NEW YORK STATE MUSEUM 



recently by G. Sherburne Rogers, the latter of whom also has given 

 much information about the emery itself (see list of references at 

 the end). 



The emery occurs as bands and irregular bodies within the 

 igneous area and seems to be distributed without rule, though it 

 rather favors the border zone than the interior of the mass. Most 

 of the emery has been rnined in the eastern part of the area, from 

 the region northeast of Pleasantside and farther south near Dickerson 

 pond and Salt hill. The farms of I. McCoy, J. H. Buckbee and 

 Oscar Dalton contain some of the larger bodies hitherto uncovered. 

 The ore is usually mined by open cutting and the work is carried 

 on mostly by hand. No deep mining by shafts has been undertaken 

 and there is very little mechanical instalation of any kind in the 

 district. The ore as mined is roughly sorted according to its appear- 

 ance and probable corundum content and hauled by truck to 

 Peekskill for shipment. 



Character. There is a great variation in the character of the 

 emery, as appears from microscopic examination of samples and 

 from results of chemical analysis. Rogers, who has made the most 

 careful study of the ores, found that corundum constituted aroimd 

 SO per cent of the mass as maximum. The best ores contain little 

 else than corundum and magnetite, which Rogers classes as " pure " 

 emery. Spinel emery contains as additional ingredient to corundum 

 and magnetite a green spinel identified as pleonaste. Feldspathic 

 emery resembles the latter but contains plagioclase which may 

 constitute one-third or one-half of the rock. In conjunction with 

 the feldspathic emery occurs a quartz variety which Rogers terms 

 emery schist and which carried 50 per cent or so of silica which 

 in the other grades normally is limited to a few per cent. Sillimanite 

 is a conspicuous ingredient of some of the ores, occurring in long 

 bladed crystals that are really distinguishable in the hand specimens. 

 It is a contact metamorphic mineral, no doubt resulting from 

 inclusions of schist in the igneous rocks. The area is bordered 

 mainly by Manhattan schist, and there are fragments of the latter 

 that have been entangled and completely surrounded by the magma 

 on its way toward the surface. 



It is from the inmelting of the aluminous-ferruginous schist that 

 Rogers explains the origin of the emery ores. Through this action 

 the magma became supersatiirated with respect to these ingredients 

 and consequently they separated out mainly as oxides. Another 

 explanation possibly applicable is that the emery ores are segrega- 

 tions of the igneous magma, without any material contribution 



