Gray, well-layered biotite-plagioclase-quartz gneiss

Containing beds of amphibolite, aluminous schist, quartzite, and calc-silicate gneiss.
State Massachusetts
Name Gray, well-layered biotite-plagioclase-quartz gneiss
Geologic age Proterozoic Y
Lithologic constituents
Major
Metamorphic > Gneisswell-layered biotite-plagioclase-quartz gneiss; and calc-silicate gneiss
Minor
Metamorphic > Amphibolite
Metamorphic > Schistaluminous schist
Metamorphic > Metasedimentary > Metaclastic > Quartzite
Comments Part of Taconic-Berkshire Zone (Ordovician and Older Rocks); in Berkshire Highlands and Green Mountain Core. Units Yb and Ybu are described together on printed map; split into two descriptions here.
References
NGMDB product
Counties Berkshire - Franklin - Hampden - Hampshire