sedimentary
Siltstone Pebble
Siltstone (primarily SiO2 with Al2O3)
Hardness: 3-5 (Mohs scale), Color: Dull gray/brown, Luster: Earthy/Dull, Structure: Clastic, fine-grained, Cleavage: None (conchoidal to irregular fracture)
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Physical properties
Hardness: 3-5 (Mohs scale), Color: Dull gray/brown, Luster: Earthy/Dull, Structure: Clastic, fine-grained, Cleavage: None (conchoidal to irregular fracture)
Formation & geological history
Formed from the lithification of silt-sized particles deposited in low-energy environments like river floodplains, lagoons, or deep-sea floors over millions of years.
Uses & applications
Commonly used as fill material, in the manufacture of cement, or as decorative pebbles in landscaping and aquariums.
Geological facts
Siltstone is intermediate between sandstone and shale; it feels gritty against the teeth but smooth to the touch compared to sandstone.
Field identification & locations
Identify in the field by its fine-grained texture and lack of fissility (splitting into layers) compared to shale. Common in sedimentary basins worldwide.
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Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
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Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
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Chert Breccia
Brecciated Chert (Microcrystalline Silica)
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Shale or Slaty Mudstone
Argillaceous sedimentary rock
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Sandstone
Arenite (primarily SiO2)
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