igneous
Basalt Pebble
Basalt
Hardness: 5-6 Mohs. Color: Black to dark gray. Luster: Dull to slightly waxy/satin when polished. Structure: Fine-grained/aphanitic. Specific gravity: 2.8-3.0.
- Hardness
- 5-6 Mohs
- Color
- Black to dark gray
- Luster
- Dull to slightly waxy/satin when polished
Identified More igneous →
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Physical properties
Hardness: 5-6 Mohs. Color: Black to dark gray. Luster: Dull to slightly waxy/satin when polished. 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 Earth's surface. This specific specimen has been smoothed by water erosion (river or beach action) or mechanical tumbling.
Uses & applications
Commonly used in landscaping, as hot stones for massage therapy, in construction as aggregate, and occasionally in jewelry as a base for wire wrapping.
Geological facts
Basalt is the most common volcanic rock on Earth and also makes up most of the ocean floors. It is even found on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight for its size, and absence of visible large crystals. Commonly found on volcanic beaches or in riverbeds downstream from volcanic mountain ranges.
