Baltimore Gneiss

Biotite-quartz-feldspar gneiss and biotite-hornblende gneiss; amphibolite widespread but subordinate; texturally varied; granitic gneiss, veined gneiss, augen gneiss, banded gneiss, and migmatite, in places complexly intermingled; age 1,1000 m.y. * by radiogenic dating. Layered paragneiss in Baltimore City southeast of Relay Quartz Diorite.
State Maryland
Name Baltimore Gneiss
Geologic age Precambrian
Lithologic constituents
Metamorphic > Gneissincludes granitic gneiss and paragneiss
Metamorphic > Metasedimentary > ParagneissLayered paragneiss in Baltimore City southeast of Relay Quartz Diorite.
Metamorphic > Amphibolite
Comments Radiogenic date from Wetherill et al., 1966 (ref. MD003)

Cleaves, E.T., Edwards, J., Jr., and Glaser, J.D., 1968, Geologic Map of Maryland: Maryland Geological Survey, Baltimore, Maryland, scale 1:250,000.

In 1995 the Water Resources Division of the U.S. Geological Survey digitized the geologic map of Maryland from the 1968 paper map (Reference MD001). Information about products from the Maryland Geological Survey can be found at

Wetherill, G.W., Tilton, G.R., Davis, G.L., Hart, S.R., and Hopson, C.A., 1966, Age measurements in the Maryland Piedmont: Journal of Geophysical Research, v. 71, p. 2139-2155.

NGMDB product
Counties Baltimore - Carroll - Harford - Howard - Baltimore