igneous
Vesicular Basalt (Aqueous Tumbled)
Scoriaceous Basalt
Hardness: 6 (Mohs); Color: Dark brown, black, with iron oxidation (orange highlights); Luster: Dull to slightly vitreous when wet; Structure: Vesicular (pitted with gas bubbles); Cleavage: None/Conchoidal.
- Hardness
- 6 (Mohs)
- Color
- Dark brown, black, with iron oxidation (orange highlights)
- Luster
- Dull to slightly vitreous when wet
Identified More igneous →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6 (Mohs); Color: Dark brown, black, with iron oxidation (orange highlights); Luster: Dull to slightly vitreous when wet; Structure: Vesicular (pitted with gas bubbles); Cleavage: None/Conchoidal.
Formation & geological history
Formed from the rapid cooling of low-viscosity, gas-rich basaltic lava at or near the Earth's surface. Extrusive igneous origin, typical of volcanic regions like Hawaii or Iceland.
Uses & applications
Used as aggregate in construction, landscaping stones, barbecue rocks, and sometimes as an abrasive (lava rock pumice). Low-grade collectors value it for teaching petrology.
Geological facts
The holes (vesicles) are created by gas bubbles that were trapped as the lava solidified. This specific specimen appears water-worn, suggesting it was recovered from a river or beach.
Field identification & locations
Identify in the field by its dark color, high density (relative to pumice), and distinctive 'Swiss cheese' porous surface. Commonly found in volcanic rift zones and coastal areas.
