igneous
Basalt Pebble
Basalt
Hardness: 6 (Mohs scale); Color: Dark grey to black; Luster: Dull to sub-metallic; Structure: Fine-grained/aphanitic; Specific Gravity: 2.8–3.0
- Hardness
- 6 (Mohs scale)
- Color
- Dark grey to black
- Luster
- Dull to sub-metallic
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Physical properties
Hardness: 6 (Mohs scale); Color: Dark grey to black; Luster: Dull to sub-metallic; Structure: Fine-grained/aphanitic; Specific Gravity: 2.8–3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava exposed at or very near the surface of a terrestrial planet or moon. Most typically associated with oceanic ridges and volcanic hotspots.
Uses & applications
Commonly used as construction aggregate, for railroad ballast, and ground into stone for heat retention in spa treatments (hot stones). Smooth pebbles are popular in landscaping and home decor.
Geological facts
Basalt is the most common rock type in the Earth's crust and covers most of the ocean floor. It is also common on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight (relative to size), and fine-grained texture. These pebbles are often found on beaches near volcanic activity or in riverbeds where volcanic rock has eroded over time.
