igneous
Basalt Scoria
Vesicular Basalt
Hardness: 5-6 Mohs; Color: black to dark brown; Luster: dull to earthy; Texture: highly vesicular (pitted with gas bubbles); Crystal Structure: fine-grained (aphanitic) or glassy
- Hardness
- 5-6 Mohs
- Color
- black to dark brown
- Luster
- dull to earthy
Identified More igneous →
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Physical properties
Hardness: 5-6 Mohs; Color: black to dark brown; Luster: dull to earthy; Texture: highly vesicular (pitted with gas bubbles); Crystal Structure: fine-grained (aphanitic) or glassy
Formation & geological history
Formed from the rapid cooling of basaltic lava containing dissolved gases. As the lava erupts, the gases expand and form bubbles (vesicles) that are trapped as the rock solidifies. Common in Cenozoic volcanic fields.
Uses & applications
Used in landscaping, high-temperature insulation, drainage rock, and as an abrasive. In construction, it is used for lightweight concrete and road base.
Geological facts
Scoria is often confused with pumice, but it is denser and darker. Because it is basaltic, it contains more iron and magnesium than the lighter-colored pumice.
Field identification & locations
Identified in the field by its dark color, heavy weight relative to its appearance (though light for a rock), and numerous open cavities. Commonly found near cinder cones and volcanic vents.
