ROGERS, GEOLOGY OF THE CORTLANDT SERIES 49 



Verplanck Point was any contact metamorphism observed : here the dikes 

 are gabbroic (camptonite), and cause the formation of diopside, actino- 

 lite or hornblende and pleonaste in the limestone. Only occasionally is a 

 typical minette, vogesite or kersantite found; usually the orthoclase and 

 plagioclase, and the biotite and hornblende, are subequal in amount.. 

 Green augite has been found only in the dikes on Verplanck Point, where 

 they radiate into the limestone; these, however, are typical camptonites. 

 Furthermore, there is seldom any serious alteration, such as is described 

 by Eosenbusch in the type lamprophyres, although this is a less essential 

 feature. Minette has not been found typically developed: the usual 

 variety is a basic one and might almost as well be called either of the 

 following. Vogesite is quite typically developed in a number of places; 

 the orthoclase constitutes two thirds or more of the feldspar, and horn- 

 blende, which is usually greenish brown, though sometimes green, is dis- 

 tinctly predominant over the biotite. Augite, however, has been seldom 

 found in them. Kersantites, though not typical, are found abundantly 

 on Verplanck Point, and also on Montrose and Stony Points. They are 

 merely fine grained mica diorites with considerable hornblende. Camp- 

 tonite occurs on Verplanck Point, as stated above. The classification of 

 these rocks according to Eosenbusch is thus a difficult matter, and they 

 had best, perhaps, be regarded as dioritic and gabbroic dikes. 



Hornblendite 



Only two dikes of hornblendite were found, one on Verplanck Point, 

 in limestone, and the other in one of the emery pits on the hill east of 

 Pleasantside, in diorite. In both cases, the rock was composed almost 

 entirely of bright green hornblende, with a very subordinate amount of 

 biotite. Apatite, which is ever-present in the diorite dikes, is practically 

 lacking. 



Serpentine {Peridotite) 



Three outcrops of serpentine (peridotite) were found, one two miles 

 east of Montrose, another four, and the third about half a mile farther. 

 The first is in hornblende norite; the others in olivine pyroxenite. The 

 first and last are undoubtedly dikes, the former three feet wide and the 

 latter about ten feet. The second outcrops on an old log road southeast of 

 Dickerson Hill, and its relations cannot be definitely determined. If a 

 dike, it must be at least twenty feet wide. In all three cases, the rock is 

 greenish black, fairly soft and strongly jointed. Tn the first case, the 

 structure of the serpentine is hard to work out. There are traces of 



