Cobble Mountain Formation

Light-brown, fine- to medium-grained pelitic schist and granofels locally graded in beds less than 15 cm thick. Local amphibolite. Rare calc-silicate rock, feldspar gneiss, coticule and cummingtonite schist.
State Massachusetts
Name Cobble Mountain Formation
Geologic age Middle Ordovician
Lithologic constituents
Major
Metamorphic > Schist > Pelitic-schistfine- to medium-grained pelitic schist and granofels locally graded in beds less than 15 cm thick; rare cummingtonite schist
Metamorphic > Granoblastic > Granofelsfine- to medium-grained pelitic schist and granofels locally graded in beds less than 15 cm thick; rare cummingtonite schist
Minor
Metamorphic > Amphibolite
Incidental
Metamorphic > Metasedimentary > Calc-silicate-rock
Metamorphic > Gneissfeldspar gneiss
Comments Part of Rowe-Hawley Zone (Ordovician and Older Rocks)
References
NGMDB product
Counties Hampden