the.com/siltstone
Mud's uptight middle sibling: too fine for sandstone, too gritty for shale.
means A fine-grained sedimentary rock made of compacted silt particles, intermediate in texture between coarse sandstone and smooth, flaky mudstone or shale.
from The word is a straightforward 19th-century geological compound: 'silt' plus 'stone.' 'Silt' itself likely traces back to a Germanic root related to 'salt' or to words for sediment left by water — it originally described the fine sand or mud deposited by rivers and tides. Geologists needed a tidy name for rock made of this grain size, lodged squarely between sand and clay, so they simply bolted 'stone' onto it. No myth, no drama — just classification doing what classification does.
- grain size
- between 0.004 and 0.06 millimeters, officially
- feel test
- gritty on teeth, unlike silky claystone
- formation
- settles in calm water, lakes or floodplains
- fossil habit
- often preserves ripple marks and footprints well