igneous
Purple Lava Rock / Vesicular Basalt
Vesicular Basalt (Mafic Extrusive Igneous Rock)
Hardness: 5-6 on the Mohs scale. Color: Purplish-grey to brown (purple tint often due to mineral staining or hematite/manganese oxidation). Luster: Dull or earthy. Crystal Structure: Aphanitic (fine-grained) with prominent vesicular texture (gas cavities/holes). Cleavage: None. Specific Gravity: 2.7-3.0.
- Hardness
- 5-6 on the Mohs scale
- Luster
- Dull or earthy
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Physical properties
Hardness: 5-6 on the Mohs scale. Color: Purplish-grey to brown (purple tint often due to mineral staining or hematite/manganese oxidation). Luster: Dull or earthy. Crystal Structure: Aphanitic (fine-grained) with prominent vesicular texture (gas cavities/holes). Cleavage: None. Specific Gravity: 2.7-3.0.
Formation & geological history
Formed from gas-rich mafic lava (basalt) that erupted at or near the Earth's surface. As the lava cooled rapidly, trapped volcanic gases expanded and escaped, leaving behind numerous cavities (vesicles).
Uses & applications
Used in landscaping, decorative stone, barbecue grills, filtration media, lightweight aggregate, and geological collections.
Geological facts
Vesicular basalt is one of the most common rock types on Earth's crust as well as the surfaces of the Moon and Mars, primarily forming the dark volcanic plains known as maria on the Moon.
Field identification & locations
Easily identified by its lightweight nature, dark color, and sponge-like or pitted vesicular texture. Commonly found in volcanic regions worldwide, including Hawaii, Iceland, the Western United States, and various ancient volcanic provinces.
