igneous
Vesicular Basalt or Porphyritic Rhyolite
Extrusive Igneous Rock
Hardness: 6-7 (depending on mineral content), Color: Grayish-pink with dark spots and small pits (vesicles), Luster: Dull to sub-vitreous, Crystal structure: Aphanitic (fine-grained) with visible phenocrysts and small cavities.
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Physical properties
Hardness: 6-7 (depending on mineral content), Color: Grayish-pink with dark spots and small pits (vesicles), Luster: Dull to sub-vitreous, Crystal structure: Aphanitic (fine-grained) with visible phenocrysts and small cavities.
Formation & geological history
Formed from cooling lava flows on or near the Earth's surface. Gas bubbles escaping from the cooling lava created the pitted, vesicular texture.
Uses & applications
Used in landscaping, aggregate, and occasionally as decorative stone.
Geological facts
The presence of small holes (vesicles) indicates that volcanic gases were trapped in the molten rock as it cooled rapidly at the Earth's surface.
Field identification & locations
Look for a fine-grained matrix containing distinct mineral crystals and characteristic small cavities or pores. Commonly found near ancient or active volcanic regions.
