igneous
Basalt Pebble / River Stone
Basalt (Mafic Extrusive Igneous Rock)
Hardness: 6 on Mohs scale; Color: Dark grey to charcoal black; Luster: Matte, dull to earthy; Structure: Fine-grained (aphanitic), massive; Cleavage: None (conchoidal to uneven fracture); Specific Gravity: 2.8 - 3.0
- Hardness
- 6 on Mohs scale
- Color
- Dark grey to charcoal black
- Luster
- Matte, dull to earthy
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Physical properties
Hardness: 6 on Mohs scale; Color: Dark grey to charcoal black; Luster: Matte, dull to earthy; Structure: Fine-grained (aphanitic), massive; Cleavage: None (conchoidal to uneven fracture); Specific Gravity: 2.8 - 3.0
Formation & geological history
Formed from the rapid cooling of low-viscosity basaltic lava at or very near Earth's surface. This particular specimen has undergone extensive fluvial or coastal erosion, smoothing it into a rounded pebble shape over time.
Uses & applications
Commonly used in landscaping, river rock decor, construction aggregate, hot stone massage therapy, and general rock collecting.
Geological facts
Basalt is the most common rock type in the Earth's crust, forming the vast majority of oceanic crust. It is also found abundantly on the Moon (lunar maria) and Mars.
Field identification & locations
Identified by its dark charcoal color, uniform fine-grained texture, heaviness, and smooth, water-worn spherical or oval pebble shape. Commonly found on beaches, riverbeds, and in gravel pits worldwide.
