igneous
Basalt River Stone
Basalt (Aphanitic Mafic Igneous Rock)
Hardness: 6.0; Color: Dark grey to charcoal; Luster: Dull/Earthy (weathered); Crystal structure: Microcrystalline; Specific gravity: 2.8-3.0
- Hardness
- 6
- Color
- Dark grey to charcoal
- Luster
- Dull/Earthy (weathered)
Identified More igneous →
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Physical properties
Hardness: 6.0; Color: Dark grey to charcoal; Luster: Dull/Earthy (weathered); Crystal structure: Microcrystalline; Specific gravity: 2.8-3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. This specimen shows significant rounding due to water erosion (fluvial transport).
Uses & applications
Commonly used in construction as aggregate, for stone walls, and sometimes in landscaping or as massage stones.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. It also exists on the Moon and Mars.
Field identification & locations
Identify by its heavy weight (density), fine-grained texture with no visible crystals, and rounded, smooth surface if found in or near water. Very common in volcanic regions and riverbeds.
