igneous
Vesicular Basalt River Rock
Vesicular Basalt
Hardness: 6 (Mohs scale); Color: Brownish-grey to olive-drab; Luster: Dull/Earthy; Structure: Aphanitic with vesicles (pitted); Specific Gravity: 2.8-3.0.
- Hardness
- 6 (Mohs scale)
- Color
- Brownish-grey to olive-drab
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6 (Mohs scale); Color: Brownish-grey to olive-drab; Luster: Dull/Earthy; Structure: Aphanitic with vesicles (pitted); Specific Gravity: 2.8-3.0.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at the surface. The small holes (vesicles) were created by gas bubbles trapped in the lava during solidification. This specimen has been smoothed and rounded by water transport in a river or stream.
Uses & applications
Common varieties are used in construction (road base), landscaping, and as aquarium stones. Pitted specimens are sometimes used as natural pumice-like scrub stones.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. When the gas bubbles in vesicular basalt are later filled by other minerals like calcite or quartz, the rock is called amygdaloidal basalt.
Field identification & locations
Identify in the field by its dense, fine-grained texture and characteristic pitting. It is commonly found in volcanic regions, particularly near riverbeds that drain basaltic plateaus.
