GeoMiner Free earth-science tools

Built by a geologist

Gneiss identification and geology

A high-grade metamorphic rock characterized by gneissic banding—alternating light and dark compositional layers—formed under high temperature and pressure during regional metamorphism. Light bands are rich in felsic minerals quartz, feldspar , while dark bands contain mafic minerals biotite, hornblende . Gneiss has a coarser grain size than schist and represents higher metamorphic conditions. Field: petrology. Example: The Acasta Gneiss in the Northwest Territories of Canada, dated at approximately 4.03 billion years, is one of the oldest known rocks on Earth and preserves evidence of very early continental crust formation.. Related terms: Schist, Foliation, Regional metamorphism, Migmatite.

Sources, scope & corrections

These authoritative resources support category-level nomenclature, terminology, identification methods, and safety. When a specimen-specific safety warning appears, the public-health source listed here directly supports that precaution. They are not line-by-line citations for every other property on this entry, and natural specimens vary.

Editorial owner
GeoMiner
Last updated
2026-03-30T15:19:41.999576+00:00
Review status
Published; not independently peer-reviewed
  • USGS Thesaurus — U.S. Geological Survey. Controlled earth-science terminology used to describe USGS information resources.
  • Glossary of Geologic Terms — U.S. National Park Service. Geologic definitions prepared by the NPS Geologic Resources Inventory.

Read GeoMiner's editorial methodology or report a content issue.

Common questions

What does Gneiss mean in geology?
A high-grade metamorphic rock characterized by gneissic banding—alternating light and dark compositional layers—formed under high temperature and pressure during regional metamorphism. Light bands are rich in felsic minerals quartz, feldspar , while dark bands contain mafic minerals biotite, hornblende . Gneiss has a coarser grain size than schist and represents higher metamorphic conditions.
What is an example of Gneiss?
The Acasta Gneiss in the Northwest Territories of Canada, dated at approximately 4.03 billion years, is one of the oldest known rocks on Earth and preserves evidence of very early continental crust formation.
Which earth-science field uses the term Gneiss?
Gneiss is used in petrology.
Which terms are related to Gneiss?
Related terms in this reference are Schist, Foliation, Regional metamorphism, Migmatite.

JavaScript is loading the interactive GeoMiner experience. The identification tools provide educational candidates, not laboratory confirmation.