igneous
Basalt River Stone
Basalt (Aphanitic Mafic Volcanic Rock)
Hardness: 5-6 (Mohs scale), Color: Dark grey to black, Luster: Dull to waxy when polished, Crystal structure: Microcrystalline (aphanitic), Specific gravity: 2.8-3.0
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Physical properties
Hardness: 5-6 (Mohs scale), Color: Dark grey to black, Luster: Dull to waxy when polished, Crystal structure: Microcrystalline (aphanitic), Specific gravity: 2.8-3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the surface of a terrestrial planet or a moon. Often smoothed into an oval shape by fluvial (river) or coastal erosion.
Uses & applications
Commonly used in landscaping, as massage stones in spas, in construction as aggregate, and in aquarium decor.
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
Identified by its dark color, heavy weight for its size, and absence of visible crystals. Commonly found in riverbeds, glacial tills, and volcanic regions.
