igneous
Basalt River Stone with Quartz Vein
Basalt (Mafic volcanic rock)
Hardness: 6-7 on Mohs scale; Color: Dark grey to black with a tan/white quartz vein; Luster: Dull to sub-vitreous; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8-3.0
- Hardness
- 6-7 on Mohs scale
- Color
- Dark grey to black with a tan/white quartz vein
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Dark grey to black with a tan/white quartz vein; Luster: Dull to sub-vitreous; Crystal structure: Aphanitic (fine-grained); 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. The visible vein formed later when mineral-rich hydrothermal fluids filled a crack in the rock and crystallized.
Uses & applications
Used primarily in construction (crushed stone), decorative landscaping, and as river rocks for aesthetic garden paths or 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 is similar in composition to rocks found on the Moon and Mars.
Field identification & locations
Identify by its heavy weight (density), dark color, and fine-grained texture. To find in the field, look in volcanic regions or riverbeds where water has rounded the stones over time.
