Hornblende gneiss and amphibolite

Dark-gray to mottled, fine- to medium-grained, massive to foliated amphibolite and gneiss, composed of hornblende and plagioclase, also commonly biotite and minor quartz; commonly interlayered with banded felsic gneiss. Locally contains calc-silicate rock or diopsidic calcite marble.
State Connecticut
Name Hornblende gneiss and amphibolite
Geologic age Proterozoic Y
Lithologic constituents
Major
Metamorphic > GneissDark-gray to mottled, fine- to medium-grained, massive to foliated amphibolite and gneiss, composed of hornblende and plagioclase, also commonly biotite and minor quartz; commonly interlayered with banded felsic gneiss.
Metamorphic > AmphiboliteDark-gray to mottled, fine- to medium-grained, massive to foliated amphibolite and gneiss, composed of hornblende and plagioclase, also commonly biotite and minor quartz; commonly interlayered with banded felsic gneiss.
Incidental
Metamorphic > Metasedimentary > Metacarbonate > MarbleLocally contains diopsidic calcite marble.
Metamorphic > Metasedimentary > Calc-silicate-rockLocally contains calc-silicate rock.
Comments Part of Western Uplands; Proto-North American (Continental) Terrane - Proterozoic Massifs - ""Grenville""
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 - Hartford - Litchfield