Locally, the felsic gneisses contain segregations of quartz and plagioclase with a single magnetite grain in the core. The magnetite grains range in size from 2 to 4 mm, and the plagioclase-quartz mantles range from 5 to 8 mm. All of the amphibolites consist of sub-equal amounts of plagioclase and hornblende with or without minor quartz. These coarser amphibolites may be metamorphosed gabbros, whereas the finer-grained amphibolites are of unknown origin. Pegmatite Throughout the Delaware Piedmont there are numerous local bodies of medium to coarse-grained granitic pegmatite.
Some pegmatites contain tourmaline, garnet, or beryl as accessory minerals.
The pegmatites in the Red Mill Road and Harmony Road cores are intrusive, coarse-grained, and undeformed.