460 



Report of the State Geologist. 



rock. The second also branches, and is about two feet wide. It cuts both 

 the gneiss and a granite vein. The gneiss strikes N. 45° E., and dips 

 60 to 70° E. 



In the bed of the stream along the road, at a point about one-half mile 

 north of the cross-road coining over the mountain from Highland Mills to 

 Forest of -Dean, are two additional camptonite dikes, cutting the gneiss parallel 

 to each other. The one is four inches wide and contains phenocrysts of horn- 

 blende a sixteenth of an inch in diameter; the other is six feet wide and 

 contains none. Sections show plagioclase, hornblende and magnetite of the 



Figure 22. Dike of cami>tonite, C, cutting a granitic gneiss, G., one mile east of Stockbridge's hotel, 

 near Central Valley, and showing inclusion of the wall-rock. 



habit common to this class of rocks. The large hornblendes of the first 

 generation are both zonal and twinned. These dikes are close to the curious 

 pyroxene-scapolite ridge of rock. 



Still other dikes of this kind occur north of the Forest-of-Dean mine, 

 and at a point along the road south of Little Long pond, also about two 

 miles east of the mine. 



The great abundance of these dikes in this region and their constantly 

 close similarity suggest very forcibly a common derivation, but whether the 



