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Brimfield Schist (Includes Hamilton Resevoir Formation) (uncertain)

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Gray, rusty-weathering, medium- to coarse-grained, interlayered schist and gneiss, composed of oligoclase, quartz, K-feldspar, and biotite, and commonly garnet, sillimanite, graphite, and pyrrhotite. K-feldspar partly as augen 1 to 3 cm across. Minor layers and lenses of hornblende- and pyroxene-bearing gneiss, amphibolite, and calc-silicate rock.
State Connecticut
Name Brimfield Schist (Includes Hamilton Resevoir Formation) (uncertain)
Geologic age Upper? and Middle Ordovician
Lithologic constituents
Major
Metamorphic > SchistGray, rusty-weathering, medium- to coarse-grained, interlayered schist and gneiss, composed of oligoclase, quartz, K-feldspar, and biotite, and commonly garnet, sillimanite, graphite, and pyrrhotite. K-feldspar partly as augen 1 to 3 cm across.
Metamorphic > GneissGray, rusty-weathering, medium- to coarse-grained, interlayered schist and gneiss, composed of oligoclase, quartz, K-feldspar, and biotite, and commonly garnet, sillimanite, graphite, and pyrrhotite. K-feldspar partly as augen 1 to 3 cm across; minor layers and lenses of hornblende- and pyroxene-bearing gneiss.
Minor
Metamorphic > Metasedimentary > Calc-silicate-rock
Metamorphic > Amphibolite
Comments Part of Eastern Uplands; Iapetus (Oceanic) Terrane - Merrimack Synclinorium; Brimfield Schist and equivalent formations (includes Tatnic Hill Formation) (Upper? and Middle Ordovician). Same as Obr
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 Middlesex - New London - Tolland - Windham