noun
shale
SHAYL/ʃeɪl/
A fine-grained sedimentary rock that splits easily into thin layers.
The dark shale along the trail splits into thin layers.
Etymology
Shale may come from schale, meaning a shell, husk, or scale. The possible connection is the rock’s tendency to split into thin layers, like coverings that separate or peel away.
In context
Material like clay or fine grained sedimentary rocks like shale, or unfractured metamorphic or igneous rocks such as granite have such low permeability values that they often act as barriers to groundwater flow.
More examples
- A small fossil is visible in this piece of shale.
- Water seeps through cracks in the shale beneath the field.
- These shales formed from mud deposited in an ancient lake.
Forms
shale · shales
shaly adjective — Containing shale or resembling its layered structure.
Similar words
- mudstone
- Similar fine-grained sedimentary rock, but lacking shale's easily split layers.
- slate
- Also splits into thin sheets, but is metamorphic rather than sedimentary.