igneous
Vesicular Basalt
Extrusive mafic igneous rock (primarily Plagioclase Feldspar and Pyroxene)
Hardness: 6 (Mohs scale); Color: Dark gray to reddish-brown (weathered); Luster: Dull/Earthy; Structure: Vesicular (pitted with gas bubbles); Specific Gravity: 2.8 - 3.0
- Hardness
- 6 (Mohs scale)
- Color
- Dark gray to reddish-brown (weathered)
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6 (Mohs scale); Color: Dark gray to reddish-brown (weathered); Luster: Dull/Earthy; Structure: Vesicular (pitted with gas bubbles); Specific Gravity: 2.8 - 3.0
Formation & geological history
Formed from the rapid cooling of magnesium and iron-rich lava at the Earth's surface. The pits (vesicles) are created by gas bubbles trapped in the cooling magma. Ages range from modern flows to billions of years old.
Uses & applications
Used in construction as road base, railroad ballast, and concrete aggregate. Highly porous specimens are used in landscaping, gas grills, and aquarium filtration.
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 heavy weight (density) for its size, dark interior, and distinctive 'Swiss cheese' texture. Commonly found in volcanic fields like the Pacific Northwest, Hawaii, or Iceland.
