sedimentary
Siltstone Pebble
Siltstone (composed of siliciclastic grains)
Hardness: 3-5 (Mohs scale), Color: Dull gray to brownish-gray, Luster: Earthy/dull, Texture: Gritty/fine-grained, Structure: Clastic, Cleavage: None
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Physical properties
Hardness: 3-5 (Mohs scale), Color: Dull gray to brownish-gray, Luster: Earthy/dull, Texture: Gritty/fine-grained, Structure: Clastic, Cleavage: None
Formation & geological history
Formed from the lithification of silt-sized particles (larger than clay but smaller than sand) deposited in low-energy environments like lake beds or floodplains. Typically millions of years old.
Uses & applications
Commonly used as fill material in construction, as decorative river rock in landscaping, and occasionally as a substrate in aquariums.
Geological facts
Siltstones are distinct from shales because they lack the fissility (layering) to split into thin sheets. They often contain micro-fossils or ripple marks from ancient currents.
Field identification & locations
Identified by its fine-grained texture that feels slightly gritty on the teeth or when rubbed against a fingernail. Commonly found on beaches, riverbeds, and in sedimentary basins worldwide.
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