igneous
Basalt (Vesicular)
Basalt
Hardness: 6 (Mohs), Color: dark grey to black or reddish-brown (when oxidized), Lustre: dull or earthy, Crystal structure: Aphanitic (fine-grained), includes vesicles (gas bubbles).
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Physical properties
Hardness: 6 (Mohs), Color: dark grey to black or reddish-brown (when oxidized), Lustre: dull or earthy, Crystal structure: Aphanitic (fine-grained), includes vesicles (gas bubbles).
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. Small pits are gas bubbles trapped during solidification.
Uses & applications
Commonly used as crushed stone for road construction, concrete aggregate, and railroad ballast. Porous varieties are sometimes used in landscaping.
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 (dense), and fine-grained texture. Found near volcanic regions, oceanic ridges, and riverbeds where volcanic rocks have washed down.
