three rocks sitting on top of a wooden floor next to each other with holes in them

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Vesicular Basalt

What causes the vesicles or pits in the rock? Here's what happens: The basalt-making molten rock cools down quickly before gas bubbles from deep inside Earth's surface have the chance to make their way out. When the lava reaches the atmosphere, the bubbles inside can blow out, leaving spherical-pitted impressions.

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Minerals And Gemstones