igneous
Basalt Pebble
Aphanitic Igneous Rock / Basalt
Hardness: 6 on Mohs scale, Color: Dark grey to black, Luster: Dull to sub-vitreous, Crystal structure: Microcrystalline or cryptocrystalline (aphanitic texture), Specific gravity: 2.8 - 3.0
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Physical properties
Hardness: 6 on Mohs scale, Color: Dark grey to black, Luster: Dull to sub-vitreous, Crystal structure: Microcrystalline or cryptocrystalline (aphanitic texture), Specific gravity: 2.8 - 3.0
Formation & geological history
Formed from the rapid cooling of low-viscosity, iron- and magnesium-rich lava exposed at or very near the Earth's surface, often rounded into a pebble through water action in rivers or shorelines.
Uses & applications
Used in construction, aggregate, road building, railroad ballast, and occasionally for decorative landscaping or hot stone massage.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the ocean basins and is also found abundantly on the Moon and Mars.
Field identification & locations
Identify by its dark, fine-grained appearance, high density, and lack of visible mineral crystals without a microscope. Commonly found worldwide along volcanic regions, riverbeds, and beaches.
