Shale is a fine-grained sedimentary rock formed from the compaction of silt and clay-sized mineral particles. It is defined by its characteristic fissility, allowing it to split into thin, parallel layers along bedding planes. It is the most abundant sedimentary rock on Earth and frequently contains fossils or organic material.
Is this shale?
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 shale with a known reference. Shale sits at Mohs 2-3, softer than the next harder reference, harder than the previous one.
- 2Read the textureLook at a fresh break with a hand lens. Texture: Fissile; splits into thin layers under 1 cm thick. Grain size: Fine-grained (particles under 0.0625 mm).
- 3Pick out the mineralsComposition: Clay mineral flakes with silt-sized fragments of other minerals, especially quartz and calcite. Identify the two or three most abundant grains.
- 4Read the lusterHold the specimen under a strong light. Luster: dull.
- 5Match the color rangeCompare against the expected color range: gray, black, red, brown, green.
Often confused with
Shale vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside shale
Minerals reported to co-occur with shale. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Mohs hardness
- 2-3
- Density
- 2.0-2.6 g/cm³
- Luster
- Dull
- Transparency
- Opaque
- Rarity
- Common
- Uses
- Industrial, Construction, Collector
- Host rock
- sedimentary basins
- Texture
- Fissile; splits into thin layers under 1 cm thick
- Grain size
- Fine-grained (particles under 0.0625 mm)
- Composition
- Clay mineral flakes with silt-sized fragments of other minerals, especially quartz and calcite
Where rockhounds find shale
2 mapped spotsClassic worldwide localities
- USA
- China
- Canada
- Germany
- United Kingdom
Field-hunting tip
Where it forms: sedimentary basins. If you start seeing quartz, clay minerals, calcite in float, you are in the right ground. In the U.S., the densest reported localities are in Montana, New Jersey. Start trip planning there.
Common questions
How do you identify shale?+
Where is shale found?+
Can I find shale in the United States?+
What rocks look like shale?+
What minerals are found with shale?+
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Find shale on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
