igneous
Scoria (Lava Rock)
Scoria (extrusive volcanic rock)
Hardness: 5-6 Mohs scale; Color: Dark red, brown, black, or grey; Luster: Dull/earthy; Crystal Structure: Aphanitic/Vesicular (porous gas bubbles); Specific Gravity: High for a rock but feels light due to porosity.
- Hardness
- 5-6 Mohs scale
- Color
- Dark red, brown, black, or grey
- Luster
- Dull/earthy
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Physical properties
Hardness: 5-6 Mohs scale; Color: Dark red, brown, black, or grey; Luster: Dull/earthy; Crystal Structure: Aphanitic/Vesicular (porous gas bubbles); Specific Gravity: High for a rock but feels light due to porosity.
Formation & geological history
Formed from the rapid cooling of basaltic or andesitic lava containing dissolved gases. As gas bubbles escape during eruption, they leave behind spherical or elongated cavities called vesicles. Often found in cinder cones.
Uses & applications
Used in landscaping (lava rock), high-temperature insulation, drainage systems, lightweight concrete aggregates, and gas grill stones.
Geological facts
Unlike pumice, scoria has a density greater than water and will typically sink. It makes up the majority of volcanic cinder cones, which are the simplest type of volcano.
Field identification & locations
Identify by its dark color, rough/scoriaceous texture, and numerous small holes (vesicles). Found predominantly in volcanic regions like Iceland, Hawaii, and the Ring of Fire.
