igneous
Vesicular Basalt
Basalt
Hardness: 5-6 (Mohs scale); Color: Dark grey to black, though often weathered to lighter grey or reddish-brown; Luster: Dull or earthy; Structure: Fine-grained (aphanitic) with small pits (vesicles); Cleavage: None (conchoidal fracture).
- Hardness
- 5-6 (Mohs scale)
- Luster
- Dull or earthy
Identified More igneous →
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Physical properties
Hardness: 5-6 (Mohs scale); Color: Dark grey to black, though often weathered to lighter grey or reddish-brown; Luster: Dull or earthy; Structure: Fine-grained (aphanitic) with small pits (vesicles); Cleavage: None (conchoidal fracture).
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava (basaltic) at the Earth's surface. The vesicles are formed by trapped gas bubbles that escaped as the lava solidified. They are found in volcanic regions spanning from the Cenozoic to the Precambrian eras.
Uses & applications
Commonly used in construction as crushed stone for road base, concrete aggregate, and railroad ballast. In landscaping, it is used as decorative rock or lava rock. It is also used in the manufacturing of stone wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up the majority of the ocean floors. It is also extremely common on other planetary bodies like the Moon, Mars, and Venus.
Field identification & locations
Identify by its dark color, heavy weight (high density), and the presence of small holes or pits on the surface. Commonly found in volcanic fields, riverbeds draining volcanic areas, and coastal regions with ancient lava flows.
