What is this close-up picture? (WotsThat: Lava rock texture (macro))

Question

What object is shown in this zoomed-in close-up photo?

MarbleGhost · Accepted Answer

Lava rock texture (macro). Lava rock is often riddled with tiny holes left by gas bubbles trapped as the molten rock cooled rapidly; some varieties, like pumice, end up light enough to float on water.

Answer: Lava rock texture (macro)

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