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NEW YORK STATE MUSEUM 



and by the presence of an occasional pegmatite or granite dike in 

 the amphiboHte, as west of Pyrites (see figures 12 and 13). 



PEGMATITE DIKES 

 The pegmatite dikes of the Canton quadrangle are interesting 

 because of their extreme mineralogical simplicity. Scattered dikes 

 occur here and there over the entire southern portion of the sheet, 

 but they are developed in abundance only in the Grenville area 

 which lies north and northeast of Eddy. Here the pegmatite 

 intrusions are literally innumerable, and vary from a few inches 

 to a few yards, but average perhaps a foot, in thickness. The 





a 







b 





c 





z 



// 



// 





m% 







Fig. 13 Granite dike in amphibolite. The borders of the dike are not 

 exposed, and the exact relations are therefore obscure; but the nearest out- 

 cropping rock is gabbro-amphibolite, and it is probable that this small mass 

 cuts it. (a) Amphibolite (sheared gabbro-diorite) ; (&) granite dike; (c) 

 surficial covering. 



Two-tenths of a mile west-southwest of lower Pyrites bridge. 



country rock is predominantly micaceous schist but contains 

 abundant interlaminated and occasional interbedded limestone. 

 While seeming to favor this formation, the restriction of pegmatites 

 to the siliceous rocks is only apparent, and is due merely to the 

 areal predominance of such types over those that are more cal- 

 careous. The distribution of the pegmatitic material is fairly uni- 

 form within the boundaries of this small area. The majority of 

 the dikes are parallel to the schistosity and to the general north- 

 east trend of the larger formations. The remainder have a hit or 

 miss attitude, and are intruded at all conceivable angles with the 



