igneous
Basalt Pebble
Mafic Igneous Basalt
Hardness: 6 (Mohs scale), Color: Dark grey to black, Luster: Dull/Matte, Crystal structure: Aphanitic (fine-grained), Specific gravity: 2.8–3.0
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Physical properties
Hardness: 6 (Mohs scale), Color: Dark grey to black, Luster: Dull/Matte, 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 exposed at or very near the surface of a terrestrial planet or a moon.
Uses & applications
Commonly used in construction as aggregate, road base, and railroad ballast. Small weathered pebbles are often used in landscaping or as decorative stones.
Geological facts
Basalt is the most common volcanic rock on Earth and covers about 70 percent of the Earth's surface in the form of oceanic crust. It is also found on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight for its size, and absence of visible larger crystals. Commonly found along shorelines, riverbeds, and volcanic regions.
