igneous
Basalt River Stone
Basalt (Ma-fi-ic Extrusive Igneous Rock)
Hardness: 5-6 Mohs; Color: Dark grey to charcoal black when wet; Luster: Dull to sub-metallic; Crystal Structure: Aphanitic (fine-grained); Specific Gravity: 2.8-3.0
- Hardness
- 5-6 Mohs
- Color
- Dark grey to charcoal black when wet
- Luster
- Dull to sub-metallic
Identified More igneous →
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Physical properties
Hardness: 5-6 Mohs; Color: Dark grey to charcoal black when wet; Luster: Dull to sub-metallic; Crystal Structure: Aphanitic (fine-grained); 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 secondary-weathered and smoothed by fluvial (river) action over thousands of years.
Uses & applications
Commonly used in landscaping, as hot stones for massage therapy due to high heat retention, and in construction as crushed aggregate.
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 extensively on the Moon and Mars.
Field identification & locations
Identify by its heavy weight (density), dark color, and lack of visible large crystals. Commonly found in riverbeds, glacial tills, and coastal areas.
