sedimentary
Gravel or Pebble
Clastic Sedimentary Grain (typically composed of Quartz or Silicate minerals)
Hardness: 6-7 (if quartz-based); Color: Mixed (browns, tans, greys); Luster: Dull to earthy; Crystal Structure: Microcrystalline; Specific Gravity: varies (approx 2.6)
- Hardness
- 6-7 (if quartz-based)
- Color
- Mixed (browns, tans, greys)
- Luster
- Dull to earthy
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Physical properties
Hardness: 6-7 (if quartz-based); Color: Mixed (browns, tans, greys); Luster: Dull to earthy; Crystal Structure: Microcrystalline; Specific Gravity: varies (approx 2.6)
Formation & geological history
Formed by the mechanical weathering and erosion of pre-existing rocks, often transported and rounded by water action in streams, rivers, or coastal environments.
Uses & applications
Used extensively in construction (concrete, asphalt), landscaping, road base, and as biological filtration in aquariums.
Geological facts
Gravel is classified by size; specifically, these appear to be 'pebbles' which are clasts between 4 and 64 millimeters in diameter. They are the primary component of conglomerate rocks.
Field identification & locations
Identify by small, rounded, clastic nature. Found nearly worldwide in riverbeds, glacial deposits, and beaches. For collectors, unique colors or patterns (like agates) are preferred.
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