Collinsville Formation

Interlayered amphibolite and white felsic gneiss containing biotite, hornblende, and magnetite. Local calc-silicate beds. Coticule-bearing granofels, muscovite quartzite and amphibolite in upper part.
State Massachusetts
Name Collinsville Formation
Geologic age Middle Ordovician or older
Lithologic constituents
Major
Metamorphic > GneissInterlayered amphibolite and white felsic gneiss containing biotite, hornblende, and magnetite.
Metamorphic > AmphiboliteInterlayered amphibolite and white felsic gneiss containing biotite, hornblende, and magnetite.
Incidental
Metamorphic > Granoblastic > Granofelscoticule-bearing granofels
Metamorphic > Metasedimentary > Metaclastic > Quartzitemuscovite quartzite
Metamorphic > Metasedimentary > Calc-silicate-rocklocal calc-silicate beds
Comments Part of Bronson Hill Zone (Ordovician and Older Rocks)
References
NGMDB product
Counties Franklin