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

Next, the gneiss, fault A, and batholith B were eroded forming a nonconformity as shown with the wavy line.

From Textbooks • Jan. 1, 2017

Cette roche forme un banc ou plutôt une lentille de plus de 500 mètres de puissance intercalée au gneiss talqueux.270 XV.  Gneiss talqueux alternant avec des schistes talqueux et micacés.

From The Ascent of the Matterhorn by Whymper, Edward