Glastonbury Gneiss

Gray, medium- to coarse-grained, massive to well-foliated granitoid gneiss composed of oligoclase, quartz, microcline, and biotite (as patches), also epidote and hornblende in many areas, commonly associated with layers of amphibolite; elsewhere minor muscovite and garnet.
State Connecticut
Name Glastonbury Gneiss
Geologic age Middle? Ordovician
Lithologic constituents
Major
Metamorphic > GneissGray, medium- to coarse-grained, massive to well-foliated granitoid gneiss composed of oligoclase, quartz, microcline, and biotite (as patches), also epidote and hornblende in many areas, commonly associated with layers of amphibolite; elsewhere minor muscovite and garnet.
Minor
Metamorphic > Amphibolitecommonly associated with layers of amphibolite
Comments Part of Eastern Uplands; Iapetus (Oceanic) Terrane - Bronson Hill Anticlinorium
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 - Tolland