Brookfield Gneiss

Brookfield (dioritic and granodioritic) Gneiss (including Newtown Gneiss of Crowley, 1968) - Dark and light, commonly speckled or banded, medium- to coarse-grained, massive to poorly foliated gneiss, composed of plagioclase, biotite, and hornblende, generally with quartz and K-feldspar, the latter commonly as megacrysts 1 to 3 cm across (also plagioclase megacrysts in darker rocks), locally associated with amphibolite or hornblende schist.
State Connecticut
Name Brookfield Gneiss
Geologic age Middle? Ordovician
Lithologic constituents
Major
Metamorphic > Metaigneous > OrthogneissGneiss (dioritic and granodioritic) - Dark and light, commonly speckled or banded, medium- to coarse-grained, massive to poorly foliated gneiss, composed of plagioclase, biotite, and hornblende, generally with quartz and K-feldspar, the latter commonly as megacrysts 1 to 3 cm across (also plagioclase megacrysts in darker rocks).
Incidental
Metamorphic > Amphibolite
Metamorphic > Schist > Amphibole-schisthornblende schist
Comments Part of Central Lowlands; Iapetus (Oceanic) Terrane - Connecticut Valley Synclinorium; Newtown Gneiss of Crowley, 1968 (CT008).
References

Rodgers, John, compiler, 1985, Bedrock Geological Map of Connecticut: Connecticut Geological and Natural History Survey, Hartford, Connecticut, 2 sheets, scale 1:125,000.

NGMDB product
Counties Fairfield - Litchfield - New Haven