
Specimen of the weekMetamorphic rock
Gneiss
Gneiss (pronounced "nice") is a coarse-grained, high-grade metamorphic rock defined by a distinctive compositional layering called gneissic banding, alternating light layers rich in quartz and feldspar and darker layers dominated by biotite, hornblende, or…
- Main minerals
- Quartz, plagioclase, K-feldspar, biotite, hornblende, garnet
- Grain size
- Coarse (typically >1 mm)
- Bulk density
- ~2.65–2.87 g/cm³

















