Hornblende Gneiss

Gray-weathering, medium- to fine grained, massive to strongly-foliated hornblende-quartz-microcline- plagioclase gneiss with rare biotite and orthopyroxene. This lithology is very similar to layered pyroxene granulite (Ypg), and is considered equivalent.
State Virginia
Name Hornblende Gneiss
Geologic age Proterozoic Y
Lithologic constituents
Major
Metamorphic > Gneiss > Hornblende-gneiss
Comments Blue Ridge Basement Complex, Middle Proterozoic (Early or Pre-Grenville-Age) Gneisses
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 Loudoun