igneous
Basalt pebble
Basalt
Hardness: 6-7 on Mohs scale. Color: Dark gray to black. Luster: Dull to sub-metallic. Crystal structure: Aphanitic (fine-grained), often containing tiny crystals of plagioclase feldspar and pyroxene.
- Hardness
- 6-7 on Mohs scale
- Color
- Dark gray to black
- Luster
- Dull to sub-metallic
Identified More igneous →
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Physical properties
Hardness: 6-7 on Mohs scale. Color: Dark gray to black. Luster: Dull to sub-metallic. Crystal structure: Aphanitic (fine-grained), often containing tiny crystals of plagioclase feldspar and pyroxene.
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 to be a small water-worn pebble.
Uses & applications
Large scale basalt is used in construction (aggregate, asphalt, railroad ballast), but small pebbles are often used in decorative landscaping or aquarium gravel.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. It is also found on the Moon and Mars.
Field identification & locations
Identify in the field by its heavy weight (high density), dark color, and lack of visible large crystals. Common in volcanic regions or as river-carried pebbles.
