igneous
Basalt (River Stone)
Mafic Igneous Rock (composed of Plagioclase and Pyroxene)
Hardness: 6-7 (Mohs), Color: Dark grey to charcoal, Luster: Dull/Matte, Texture: Fine-grained (aphanitic), Structure: Dense and heavy.
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Physical properties
Hardness: 6-7 (Mohs), Color: Dark grey to charcoal, Luster: Dull/Matte, Texture: Fine-grained (aphanitic), Structure: Dense and heavy.
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 by fluvial (river) or glacial erosion over thousands of years.
Uses & applications
Commonly used in construction (road base, concrete aggregate), landscaping, and as decorative river rock. Polished versions are often used in hot stone massage therapy.
Geological facts
Basalt is the most common rock on Earth's surface and actually makes up most of the ocean floor. It is also found in abundance on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight relative to size, and fine-grained texture. Commonly found in riverbeds, beaches, and volcanic regions.
