GNEISSES IN THE HIGHLANDS OF NEW JERSEY 597 



The first is a very coarse-grained granite, almost a pegmatite in 

 texture, in which crystals of microcline, or crystalline aggregates 

 of the same mineral, occasionally attain a diameter of four or five 

 inches. Where found in the largest masses it is almost free from 

 dark minerals and consists essentially of quartz and two kinds of 

 feldspar. In such places it is very massive and shows little or no 

 indication of parallehsm in the disposition of its constituent 

 minerals. At the other extreme from this type is a finely banded 



Fig. 2 



gneiss, such as is shown in Fig. i. This photograph was taken at 

 an exposure of a large surface of glaciated rock about one-fourth 

 mile (0.4 kilometer) north of the quarry, and the relations shown 

 are typical of much of the rock in the vicinity. The light bands 

 consist principally of quartz and feldspar, while the dark bands 

 and streaks are characterized especially by large amounts of bio- 

 tite, hornblende, or chlorite mixed with the quartz and feldspar. 

 When developed in the manner shown in this photograph, either 

 the dark or the light bands may individually have any thickness up 



