Metavolcanic member [of Collins Hill Formation]

Ranges from mafic to felsic, from dark layered amphibolite and hornblende schist, locally with garnet or epidote, to light-gray (in places purplish), laminated gneiss, composed of quartz, oligoclase, and biotite, in which some layers contain garnet (generally manganiferous) and hornblende or cummingtonite.
State Connecticut
Name Metavolcanic member [of Collins Hill Formation]
Geologic age Upper? and Middle Ordovician
Lithologic constituents
Major
Metamorphic > SchistRanges from mafic to felsic, from dark layered amphibolite and hornblende schist, locally with garnet or epidote.
Metamorphic > AmphiboliteRanges from mafic to felsic, from dark layered amphibolite and hornblende schist, locally with garnet or epidote.
Metamorphic > Gneisslight-gray (in places purplish), laminated gneiss, composed of quartz, oligoclase, and biotite, in which some layers contain garnet (generally manganiferous) and hornblende or cummingtonite
Comments Part of Eastern Uplands; Iapetus (Oceanic) Terrane - Bronson Hill Anticlinorium; Brimfield Schist and equivalent formations (includes Collins Hill Formation) (Upper? and Middle Ordovician).
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 Hartford - Middlesex - New Haven