Gneiss is a high-grade metamorphic rock characterized by distinct light and dark compositional banding known as gneissic banding. It forms under intense heat and pressure from pre-existing igneous or sedimentary rocks, often resulting in a foliated texture visible to the naked eye.
Is this gneiss?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch gneiss with a known reference. Gneiss sits at Mohs 5-7, softer than the next harder reference, harder than the previous one.
- 2Read the textureLook at a fresh break with a hand lens. Texture: Gneissic banding of alternating darker and lighter layers; poorly developed schistosity. Grain size: Medium- to coarse-grained.
- 3Pick out the mineralsComposition: Recrystallized rock with few platy minerals such as mica or chlorite. Identify the two or three most abundant grains.
- 4Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 5Match the color rangeCompare against the expected color range: white, gray, pink, black.
Often confused with
Gneiss vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside gneiss
Minerals reported to co-occur with gneiss. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Mohs hardness
- 5-7
- Density
- 2.6-2.9 g/cm³
- Luster
- Vitreous
- Transparency
- Opaque
- Rarity
- Common
- Uses
- Building stone, Decorative stone, Road aggregate
- Texture
- Gneissic banding of alternating darker and lighter layers; poorly developed schistosity
- Grain size
- Medium- to coarse-grained
- Composition
- Recrystallized rock with few platy minerals such as mica or chlorite
Where rockhounds find gneiss
8 mapped spotsClassic worldwide localities
- Canada
- Scandinavia
- Scotland
- United States
Field-hunting tip
If you start seeing quartz, feldspar, mica in float, you are in the right ground. In the U.S., the densest reported localities are in Michigan. Start trip planning there.
More gneiss photos
Common questions
How do you identify gneiss?+
Where is gneiss found?+
Can I find gneiss in the United States?+
What rocks look like gneiss?+
What minerals are found with gneiss?+
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Find gneiss on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
