igneous
Basalt River Stones
Aphantic Mafic Igneous Rock (Basalt)
Hardness: 6-7 Mohs; Color: Dark grey to black; Luster: Dull/Matte (weathered); Crystal structure: Fine-grained/Aphanitic; Specific gravity: 2.8-3.0
- Hardness
- 6-7 Mohs
- Color
- Dark grey to black
- Luster
- Dull/Matte (weathered)
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Physical properties
Hardness: 6-7 Mohs; Color: Dark grey to black; Luster: Dull/Matte (weathered); Crystal 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 the earth's surface. These specific specimens have been rounded and smoothed by fluvial (river) or coastal erosion processes.
Uses & applications
Commonly used in landscaping (decorative rock), construction (as aggregate), sauna stones (due to heat retention), and massage therapy.
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 common on the Moon and Mars.
Field identification & locations
Identify in the field by its dark color, heavy weight (relative to size), and lack of visible crystals. It is commonly found in volcanic regions or as rounded cobbles in riverbeds.
