igneous
Vesicular Basalt (Scoria)
Basalt (Vesicular texture)
Hardness: 5-6 (Mohs); Color: dark gray, black, or reddish-brown; Luster: dull to earthy; Texture: vesicular (honeycombed with gas pores); Specific gravity: 2.5-3.0.
- Hardness
- 5-6 (Mohs)
- Color
- dark gray, black, or reddish-brown
- Luster
- dull to earthy
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Physical properties
Hardness: 5-6 (Mohs); Color: dark gray, black, or reddish-brown; Luster: dull to earthy; Texture: vesicular (honeycombed with gas pores); Specific gravity: 2.5-3.0.
Formation & geological history
Formed from extrusive volcanic activity. As magma reaches the surface as lava, dissolved gases expand into bubbles (vesicles) and remain trapped as the rock cools rapidly. These rocks are found in volcanic fields worldwide, ranging from prehistoric ages to recent eruptions.
Uses & applications
Used in landscaping, gas grill lava rocks, lightweight concrete aggregate, heat-insulating road sub-base, and sometimes as a decorative element in aquariums.
Geological facts
The holes in the rock are called vesicles. Because of these air pockets, some highly vesicular volcanic rocks like pumice can float (though basalt is usually too dense to do so). Basalt is the most common rock type in the Earth's crust.
Field identification & locations
Identify by its dark color, heavy weight compared to pumice, and significant surface pitting/holes. Commonly found in regions with historical volcanic activity like Hawaii, Iceland, or the Pacific Northwest.
