igneous
Vesicular Basalt (Lava Rock)
Vesicular Basalt
Hardness: 5-6 (Mohs); Color: Dark grey, brown, or black with weathered tan surfaces; Luster: Dull/Earthy; Crystal structure: Aphanitic (fine-grained) with visible vesicles (pits); Specific gravity: 2.8 - 3.0.
- Hardness
- 5-6 (Mohs)
- Color
- Dark grey, brown, or black with weathered tan surfaces
- Luster
- Dull/Earthy
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Physical properties
Hardness: 5-6 (Mohs); Color: Dark grey, brown, or black with weathered tan surfaces; Luster: Dull/Earthy; Crystal structure: Aphanitic (fine-grained) with visible vesicles (pits); Specific gravity: 2.8 - 3.0.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at the Earth's surface. The pits (vesicles) are created by gas bubbles escaping from the cooling magma. Typically Cenozoic era or younger in active volcanic regions.
Uses & applications
Used in landscaping, as a filter medium in water treatment, in road construction, and occasionally in jewelry as aromatherapy beads due to their porous nature.
Geological facts
Basalt is the most common rock in the Earth's crust and makes up most of the ocean floor. When the gas bubbles are extremely numerous, the rock becomes Scoria.
Field identification & locations
Identify by its lightweight feel relative to size (due to air pockets), dark color, and characteristic 'pitting' or holes on the surface. Commonly found near ancient or active volcanic sites.
