igneous
Basalt pebble
Aphanitic Mafic Volcanic Rock (Fe/Mg rich)
Hardness: 5-6 (Mohs); Color: dark grey to black with possible weathering; Luster: dull to earthy; Structure: fine-grained (aphanitic); Cleavage: none; Specific Gravity: 2.8-3.0
- Hardness
- 5-6 (Mohs)
- Color
- dark grey to black with possible weathering
- Luster
- dull to earthy
Identified More igneous →
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Physical properties
Hardness: 5-6 (Mohs); Color: dark grey to black with possible weathering; Luster: dull to earthy; Structure: fine-grained (aphanitic); Cleavage: none; 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 a moon. This specimen appears water-worn.
Uses & applications
Commonly used as crushed stone for road base, concrete aggregate, and railroad ballast, or for stone massage in spas.
Geological facts
Basalt is the most common rock type on Earth's crust and also makes up the majority of the lunar mare on the Moon.
Field identification & locations
Identify by its dark color, heavy weight for its size, and lack of visible crystals to the naked eye. Found worldwide in volcanic regions and riverbeds.
