igneous
Vesicular Basalt
Vesicular Basalt (rich in silicate minerals mostly Plagioclase and Pyroxene)
Hardness: 5-6 (Mohs scale), Color: Dark gray to reddish-brown, Luster: Dull or earthy, Crystal structure: Aphanitic (fine-grained), features voids (vesicles), Specific Gravity: 2.8–3.0
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Physical properties
Hardness: 5-6 (Mohs scale), Color: Dark gray to reddish-brown, Luster: Dull or earthy, Crystal structure: Aphanitic (fine-grained), features voids (vesicles), Specific Gravity: 2.8–3.0
Formation & geological history
Formed through the rapid cooling of magnesium-rich and iron-rich lava. The holes, or vesicles, are caused by gas bubbles being trapped in the lava as it solidifies at the surface.
Uses & applications
Used in landscaping, construction (as aggregate), and sometimes in spa treatments (hot stones). In larger quantities, it's used for road base.
Geological facts
Many planetary surfaces, including the Moon and Mars, are primarily composed of basalt. The vesicles in this rock can sometimes be filled with secondary minerals like quartz or calcite, creating 'amygdaloids'.
Field identification & locations
Identify it by its heavy weight (dense for its size) despite the holes, and its characteristic Swiss-cheese-like appearance. Common in volcanic regions like Hawaii, Iceland, or the Pacific Northwest.
