Highly foliated, coarse granite gneiss intrusive into the schist complex and basic rocks. Wissahickon formation Banded or laminated quartz-rich phyllites and schists and magnetite, quartz veins, sandstone and conglomerate beds composed of muscovite, chlorite, albite, quartz. Grading into coarser schist to the east. Includes some Marburg schist. May be the equivalent of Harpers to the west.
Calcareous layers are common.
Interfingers with Ijamsville phyllite. Formerly Sykesville granite. Granitic-looking schistose rock with numerous inclusions, quartz pebbles, garnets, grading into schist east and westward. Probably granitized schist.