Ardentown Granitic Suite Baltimore Gneiss Barley Mill Gneiss Biotite Tonalite Brandywine Blue Gneiss Bringhurst Gabbro Christianstead Gneiss Cockeysville Marble Faulkland Gneiss Iron Hill Gabbro Metapyroxenite and metagabbro (undifferentiated) Mill Creek Metagabbro Montchanin Metagabbro Pegmatite Perkins Run Gabbronorite Suite Rockford Park Gneiss Serpentinite Setters Formation Windy Hills Gneiss Wissahickon Formation Book traversal links for Piedmont Rock Unit Descriptions ‹ Piedmont Rock Units Up Ardentown Granitic Suite › Printer-friendly version