igneous
Basalt River Stone
Basalt (extrusive mafic rock)
Mohs hardness: 6-7; Color: dark grey to black (wet); Luster: dull to vitreous when wet; Structure: fine-grained (aphanitic), sometimes vesicular; Cleavage: none; Specific gravity: 2.8-3.0
- Hardness
- 6-7
- Color
- dark grey to black (wet)
- Luster
- dull to vitreous when wet
Identified More igneous →
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Physical properties
Mohs hardness: 6-7; Color: dark grey to black (wet); Luster: dull to vitreous when wet; Structure: fine-grained (aphanitic), sometimes vesicular; Cleavage: none; Specific gravity: 2.8-3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at the earth's surface. This specific specimen has been Rounded and smoothed by fluvial (river) or coastal erosion processes.
Uses & applications
Commonly used in construction (crushed stone), landscaping, aquarium decor, and hot stone massage therapy.
Geological facts
Basalt is the most common rock in Earth's crust and makes up most of the ocean floor. It is also found extensively on the Moon and Mars.
Field identification & locations
Identify in the field by its dark color, heavy weight for its size, and the absence of visible crystals. Commonly found in volcanic regions, riverbeds, and beaches.
