igneous
Vesicular Basalt
Vesicular Basalt
Hardness: 5-6 (Mohs scale), Color: Dark brown to black (often weathered to reddish-brown), Lustre: Dull to sub-metallic, Crystal structure: Aphanitic (fine-grained), Feature: Characterized by many small cavities called vesicles.
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Physical properties
Hardness: 5-6 (Mohs scale), Color: Dark brown to black (often weathered to reddish-brown), Lustre: Dull to sub-metallic, Crystal structure: Aphanitic (fine-grained), Feature: Characterized by many small cavities called vesicles.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava (basaltic lava) containing trapped gas bubbles. As the lava cools and solidifies quickly, the gas escapes or remains trapped, leaving behind circular or elongated pits.
Uses & applications
Used in landscaping, construction (as aggregate), road base, and occasionally in jewelry as lava beads. Smaller specimens are popular in educational geology kits.
Geological facts
The holes in the rock are called vesicles. If these holes later fill with minerals like quartz or calcite, the rock is then called amygdaloidal basalt. Basalt is the most common rock type in the Earth's crust.
Field identification & locations
Identify by its dark color, heavy weight (relative to size), and distinct 'pock-marked' or holey surface. Commonly found in volcanic regions, oceanic crust, and near plate boundaries.
