sedimentary
Siltstone River Pebble
Siltstone (primarily composed of silt-sized particles)
Hardness: 3-4 (Mohs scale); Color: Olive-drab to brownish-grey; Luster: Dull/Earthy; Crystal structure: Clastic (non-visible crystals); Cleavage: None/Irregular; Specific Gravity: 2.6-2.7
- Hardness
- 3-4 (Mohs scale)
- Color
- Olive-drab to brownish-grey
- Luster
- Dull/Earthy
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Physical properties
Hardness: 3-4 (Mohs scale); Color: Olive-drab to brownish-grey; Luster: Dull/Earthy; Crystal structure: Clastic (non-visible crystals); Cleavage: None/Irregular; Specific Gravity: 2.6-2.7
Formation & geological history
Formed by the deposition and lithification of silt-sized particles in low-energy aquatic environments such as river deltas or lake beds. This specimen has been rounded into a pebble via fluvial erosion (river action).
Uses & applications
Primarily used as decorative landscaping stones, fill material in construction, or for educational purposes in basic geology kits.
Geological facts
Siltstones are intermediate between sandstone and shale; they have smaller grains than sandstone but lack the fissility (layering) typically found in shale.
Field identification & locations
Identify by its smooth, matte texture and fine grain size that feels gritty to the teeth but smooth to the touch. It lacks the visible layers of shale. Common in riverbeds and glacial deposits throughout the world.
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