sedimentary
Siltstone Pebble
Siltstone (composed of hydraulic-sorted silt-sized particles)
Hardness: 3-4 on Mohs scale; Color: Tan to light brown with visible fine laminations; Luster: Dull/Earthy; Texture: Fine-grained, gritty feel but smoother than sandstone.
- Hardness
- 3-4 on Mohs scale
- Color
- Tan to light brown with visible fine laminations
- Luster
- Dull/Earthy
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Physical properties
Hardness: 3-4 on Mohs scale; Color: Tan to light brown with visible fine laminations; Luster: Dull/Earthy; Texture: Fine-grained, gritty feel but smoother than sandstone.
Formation & geological history
Formed by the lithification of silt-sized particles usually in river deltas, lake beds, or marine environments. The rounded shape is the result of mechanical weathering and water erosion in a high-energy environment like a beach or stream.
Uses & applications
Primarily used as fill material in construction or as decorative landscaping stones. In smaller, tumbled forms, they are often collected as river stones.
Geological facts
Siltstone is intermediate between sandstone and shale. While it looks like a simple rock, the fine layers (laminae) visible on this specimen represent different pulses of sediment deposition over time.
Field identification & locations
Identify by its fine-grained texture that is grittier than claystone but lacking the large visible grains of sandstone. Commonly found in riverbeds, glacial tills, and coastal areas.
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