36 NEW YORK STATE MUSEUM 



sharp contacts. Another exceptional place is the small body of 

 syenite just west of Mount Anthony where some pegmatites with- 

 out sharp borders cut across the foliation of the syenite. 



The various combinations of mixed rocks as mapped also not 

 rarely contain some pegmatite and silexite mostly arranged parallel 

 to the foliation, but in some cases they cut across it at various 

 angles. Among other places, such pegmatite and silexite are well 

 displayed in the mixed rock areas at and near Mount Anthony; 1^2 

 miles northwest of Corinth ; on the hill just north of Lake Luzerne ; 

 one-half of a mile southeast of Gailey hill ; and 23^ miles north of 

 Stony Creek village. The largest pegmatite dike observed cuts the 

 Grenville-granite mixed rocks between i and 15^ miles southwest 

 of Linwood school. It is described in the chapter on Mines and 

 Quarries. 



Aplite in the form of distinct dikes seldom occurs, two cases of 

 special interest being an aplite dike 2 inches wide which sharply 

 cuts the gabbro i mile southwest of Gailey hill, and another very 

 small one which very sharply cuts the little body of gabbro V/z 

 miles north of Potash mountain. 



Considerable aplitic granite does, however, occur locally as a 

 facies of the granite in the form of bands of varying width not 

 sharply separated from the granite and parallel to its foliation. 

 Such aplite appears to be a differentiation phase of the granite 

 magma. It is well exhibited on West (Hadley), Baldhead and 

 Moose mountains, and between i and 15^ miles east of Stony Creek 

 station. 



Much of the granite which has so intimately cut, injected and 

 even more or less absorbed Grenville material of the garneti- 

 ferous Grenville-granite mixed rocks in the southern third of the 

 quadrangle is distinctly light gray to nearly white, relatively fine- 

 grained, and aplitic in character. 



Diabase Dikes 



Diabase dikes are represented at twenty localities on the accom- 

 panying geologic map. Others no doubt occur, some of which are 

 concealed from view and some of which escaped detection by the 

 writer. In any case it is very certain that diabase dikes are far 

 less abundant in this district than they are in the northeastern Adi- 

 rondacks where, for example, on the writer's Lyon Mountain geo- 

 logic map more than 120 dike localities are indicated. They cut 

 all kinds of Precambrian rocks and, judging by their mode of 

 occurrence as narrow sharply defined dikes, their fineness of grain, 



