igneous
Basalt Pebble
Basalt
Hardness: 6-6.5 on Mohs scale. Color: Dark gray to black, weathered surface. Luster: Dull, earthy. Structure: Fine-grained, phaneritic/aphanitic mix (mafic composition). Cleavage: None visible.
- Hardness
- 6-6
- Color
- Dark gray to black, weathered surface
- Luster
- Dull, earthy
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Physical properties
Hardness: 6-6.5 on Mohs scale. Color: Dark gray to black, weathered surface. Luster: Dull, earthy. Structure: Fine-grained, phaneritic/aphanitic mix (mafic composition). Cleavage: None visible.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the Earth's surface. This smooth, rounded pebble shape was created through natural water erosion in a stream, river, or ocean shoreline.
Uses & applications
Commonly used in construction, crushed stone aggregate, road base, and decorative landscaping rock.
Geological facts
Basalt is the most common rock type in the Earth's crust, forming almost all oceanic crust and significant volcanic plateaus worldwide.
Field identification & locations
Identified by its dark, heavy mafic appearance, fine texture, and smooth river-worn rounded shape. Extremely common in volcanic areas, riverbeds, and ocean beaches.
