Porphyroblastic Biotite Gneiss

Light-gray, medium grained, segregation-layered gneiss, contains prominent potassium feldspar porphyroblasts. Mineralogy: quartz + biotite + plagioclase + potassium feldspar + muscovite ± hornblende; accessory minerals include epidote, apatite, and opaque minerals.
State Virginia
Name Porphyroblastic Biotite Gneiss
Geologic age Proterozoic
Lithologic constituents
Major
Metamorphic > Gneiss > Biotite-gneissporphyroblastic biotite gneiss
Comments Central Piedmont
References

Virginia Division of Mineral Resources, 1993, Geologic Map of Virginia: Virginia Division of Mineral Resources, scale 1:500,000.

Virginia Division of Mineral Resources, 2003, Digital Representation of the 1993 Geologic Map of Virginia, Publication 174, CD ROM (ISO-9660) contains image file, expanded explanation in pdf, and ESRI shapefiles, scale 1:500,000.

NGMDB product
Counties Amelia - Cumberland - Goochland - Powhatan - Prince Edward