igneous
Vesicular Basalt / Scoria pebble
Extrusive igneous rock with amygdaloidal infilling
Hardness: 6 on the Mohs scale, Color: Brownish-gray with white mineral infills, Luster: Dull to sub-vitreous, Texture: Porphyritic and vesicular with secondary mineral fillings (likely quartz or calcite)
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Physical properties
Hardness: 6 on the Mohs scale, Color: Brownish-gray with white mineral infills, Luster: Dull to sub-vitreous, Texture: Porphyritic and vesicular with secondary mineral fillings (likely quartz or calcite)
Formation & geological history
Formed from gas-rich mafic lava that cooled rapidly on the Earth's surface, trapping gas bubbles (vesicles) which were later partially filled by secondary hydrothermal mineral deposits.
Uses & applications
Used locally in landscaping, construction aggregate, and as a natural tumbled specimen for rock collectors.
Geological facts
The holes in the rock are called vesicles, created by expanding volcanic gases as the lava solidified. When these cavities are later filled with minerals like quartz or calcite, they are termed amygdules.
Field identification & locations
Found commonly in volcanic regions and riverbeds where volcanic rocks have been transported and rounded by water. Identified by its pitted, vesicular surface and relatively heavy weight for its size due to mafic mineral content.
