College Hill Granite Gneiss

Light-gray to medium-dark-gray, porphyritic biotite-microcline-perthite granodioritic gneiss and pegmatite. Strongly deformed, lineated, and saturated with less deformed later pegmatite; grades outward into a migmatitic border exhibiting decreasing concentration of microcline megacrysts. Forms a single large intrusive mass on College Hill in Jamaica and west of Stratton Mountain; truncates structure in older gneisses. U-Pb zircon TIMS age of 1,244±8 Ma, no. 11 (Ratcliffe and others, 1991; Aleinikoff and others, 2011). Stratton Mountain Intrusive Suite (Middle Mesoproterozoic) (1,244±8 Ma to 1,221±4 Ma). Mount Holly Complex intrusive rocks. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes.
State Vermont
Name College Hill Granite Gneiss
Geologic age Middle Mesoproterozoic
Lithologic constituents
Metamorphic > Metasedimentary > ParagneissLight-gray to medium-dark-gray, porphyritic biotite-microcline-perthite granodioritic gneiss.
Igneous > Plutonic > Granitic > Leucocratic-granitic > Pegmatite
NGMDB product
Counties Bennington - Windham