Collinsville Formation

Amphibolite and minor plagioclase gneiss. Magnetite-hornblende granofels near top.
State Massachusetts
Name Collinsville Formation
Geologic age Middle Ordovician or older
Lithologic constituents
Major
Metamorphic > Amphibolite
Minor
Metamorphic > Gneissplagioclase gneiss
Incidental
Metamorphic > Granoblastic > Granofelsmagnetite-hornblende granofels
Comments Part of Bronson Hill Zone (Ordovician and Older Rocks)
References
NGMDB product
Counties Hampden