igneous
Vesicular Basalt with Secondary Mineral Infill
Mafic Volcanic Rock (Basalt)
Hardness: 5-6 (Mohs); Color: Dark brown to reddish-purple matrix with white/grey mineral patches; Luster: Dull or earthy; Structure: Aphanitic with vesicles; Specific Gravity: 2.8-3.0.
- Hardness
- 5-6 (Mohs)
- Luster
- Dull or earthy
Identified More igneous →
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Physical properties
Hardness: 5-6 (Mohs); Color: Dark brown to reddish-purple matrix with white/grey mineral patches; Luster: Dull or earthy; Structure: Aphanitic with vesicles; Specific Gravity: 2.8-3.0.
Formation & geological history
Formed through the rapid cooling of magnesium-rich and iron-rich lava at the Earth's surface. The holes (vesicles) are created by trapped gas bubbles. The white patches are secondary minerals like calcite or zeolites that deposited in these voids later via groundwater.
Uses & applications
Commonly used as aggregate in construction, road base, and concrete. In landscaping, it is used for decorative ground cover or garden features.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. The reddish color in this specimen indicates the oxidation of iron-rich minerals (weathering).
Field identification & locations
Identify by its heavy weight, dark fine-grained texture, and gas bubble holes. It is found in volcanic regions worldwide, such as the Pacific Northwest, Hawaii, and Iceland.
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