igneous
Vesicular Basalt
Basalt (extrusive volcanic rock)
Hardness: 5-6 Mohs. Color: Dark grey to black, often weathering to brownish or greenish. Luster: Dull to earthy. Structure: Vesicular (containing small cavities or pits called vesicles). Specific gravity: 2.8-3.0.
- Hardness
- 5-6 Mohs
- Color
- Dark grey to black, often weathering to brownish or greenish
- Luster
- Dull to earthy
Identified More igneous →
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Physical properties
Hardness: 5-6 Mohs. Color: Dark grey to black, often weathering to brownish or greenish. Luster: Dull to earthy. Structure: Vesicular (containing small cavities or pits called vesicles). Specific gravity: 2.8-3.0.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. The pits (vesicles) are created by gas bubbles that were trapped in the lava as it solidified. Most specimens are from the Cenozoic era, though they can be found from almost any geological age.
Uses & applications
Commonly used as aggregate in construction (roads and concrete), for railroad ballast, and in landscaping or as aquarium stones. Low-density varieties are sometimes used for insulation or as abrasive stones.
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 extensively on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight compared to other light-colored rocks, and the presence of small rounded holes (pits). It is commonly found in volcanic regions such as the Pacific Northwest, Hawaii, and Iceland.
