igneous
Basalt (Water-worn Pebble)
Basalt
Hardness: 6-7 on Mohs scale; Color: dark grey to black; Luster: dull to sub-metallic; Crystal structure: fine-grained (aphanitic); Specific gravity: 2.8-3.0
- Hardness
- 6-7 on Mohs scale
- Color
- dark grey to black
- Luster
- dull to sub-metallic
Identified More igneous →
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Physical properties
Hardness: 6-7 on Mohs scale; Color: dark grey to black; Luster: dull to sub-metallic; Crystal 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 at or very near the surface of a terrestrial planet or moon. This specific piece shows rounding from fluvial or coastal erosion.
Uses & applications
Commonly used as an aggregate in construction, road base, concrete, and sometimes for ornamental stone 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 also covers vast areas of the Moon, known as the lunar maria.
Field identification & locations
Identify by its dark color, heavy weight (relative to size), and lack of visible crystals. It is frequently found on beaches and in riverbeds near volcanic regions.
