Cobble Mountain Formation

Thick-bedded (15 to 40 cm), nonrusty-weathering, silvery-gray, medium- to coarse-grained mica gneiss interlayered with nonrusty-weathering mica schist and minor amphibolite.
State Massachusetts
Name Cobble Mountain Formation
Geologic age Middle Ordovician
Lithologic constituents
Major
Metamorphic > Schist > Mica-schistinterlayered with nonrusty-weathering mica schist
Metamorphic > Gneissnonrusty-weathering, silvery-gray, medium- to coarse-grained mica gneiss
Minor
Metamorphic > Amphibolite
Comments Part of Rowe-Hawley Zone (Ordovician and Older Rocks)
References
NGMDB product
Counties Hampden - Hampshire