| Port Deposit Gneiss | |
| Type: | metamorphic |
| Age: | Paleozoic |
| Period: | Paleozoic |
| Prilithology: | gneiss |
| Namedfor: | Port Deposit, Maryland |
| Region: | Piedmont of Maryland |
| Extent: | eastern Maryland |
The Port Deposit Gneiss is a Paleozoic gneiss formation in Cecil County, Maryland. It is described as a "Moderately to strongly deformed intrusive complex, chiefly composed of quartz diorite gneiss. Rock types include gneissic biotite-quartz diorite, hornblende-biotite-quartz diorite, and biotite granodiorite, with minor amounts of quartz monzonite and hornblende-quartz diorite. Moderate protoclastic foliation grades into strong cataclastic shearing."[1] It intrudes into the Volcanic Complex of Cecil County.
The Port Deposit Gneiss has been quarried along the east as well as the west bank of the Susquehanna River for over 100 years.
Port Deposit Gneiss was used in:[2]