gneiss

American  

[nahys] / naɪs /

noun

1. a metamorphic rock, generally made up of bands that differ in color and composition, some bands being rich in feldspar and quartz, others rich in hornblende or mica.

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gneiss British  

/ naɪs /

noun

1. any coarse-grained metamorphic rock that is banded and foliated: represents the last stage in the metamorphism of rocks before melting

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gneiss Scientific  

/ nīs /

1. A highly foliated, coarse-grained metamorphic rock consisting of light-colored layers, usually of quartz and feldspar, alternating with dark-colored layers of other minerals, usually hornblende and biotite. Individual grains are often visible between layers. Gneiss forms as the result of the regional metamorphism of igneous, sedimentary, or other metamorphic rocks.

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Other Word Forms

• gneissic adjective

Etymology

Origin of gneiss

Borrowed into English from German around 1750–60

Compare meaning

How does gneiss compare to similar and commonly confused words? Explore the most common comparisons:

• gneiss vs. granite
• schist vs. gneiss

Example Sentences

The company is now training modern exploration techniques on outcroppings of a 1.8-billion-year-old type of metamorphic rock called Pinto gneiss.

From Los Angeles Times • Mar. 30, 2026

The oldest rock with a reliable age—a gneiss from Canada—is 4.03 billion years old.

From Science Magazine • Apr. 30, 2024

In front of me, a sheer wall of stippled gneiss.

From New York Times • Aug. 22, 2022

These crystalline changes create identifying textures, which is shown in the figure below comparing the phaneritic texture of igneous granite with the foliated texture of metamorphic gneiss.

From Textbooks • Jan. 1, 2017

Everywhere,417 even up to the highest summit, the gneiss is decomposed on the surface into laterit-like products.

From Narrative of the Circumnavigation of the Globe by the Austrian Frigate Novara, Volume I (Commodore B. Von Wullerstorf-Urbair,) Undertaken by Order of the Imperial Government in the Years 1857, 1858, & 1859, Under the Immediate Auspices of His I. and R. Highness the Archduke Ferdinand Maximilian, Commander-In-Chief of the Austrian Navy. by Scherzer, Karl Ritter von