sedimentary
Banded Mudstone (Siltstone Pebble)
Siltstone / Argillite (Fossiliferous Mudstone)
Hardness: 3-4 (Mohs); Color: Grey, olive green, cream; Luster: Dull/Earthy; Crystal structure: Microcrystalline; Cleavage: None/Conchoidal.
- Hardness
- 3-4 (Mohs)
- Color
- Grey, olive green, cream
- Luster
- Dull/Earthy
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Physical properties
Hardness: 3-4 (Mohs); Color: Grey, olive green, cream; Luster: Dull/Earthy; Crystal structure: Microcrystalline; Cleavage: None/Conchoidal.
Formation & geological history
Formed from the lithification of fine-grained clay and silt particles in low-energy aquatic environments; may belong to the Cretaceous or Paleogene periods depending on local coastal geology.
Uses & applications
Primarily used as a decorative garden stone or naturally polished beach pebble; larger deposits used in cement production or as fill material.
Geological facts
The distinct banding and smooth, rounded shape are the result of thousands of years of abrasion by waves and tides in a high-energy coastal environment.
Field identification & locations
Look for rounded, smooth stones with distinct horizontal layers or color zones. Common on flysch-coastlines and riverbanks. Easily identified by its fine-grained texture compared to sandstone.
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Sandstone or Siltstone
Arenite (if sandstone)
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Fossiliferous Concretion
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Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
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Shale
Argillaceous sedimentary rock
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