What is this close-up picture? (WotsThat: Limestone rock surface (macro))

Question

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

ObsidianPulse · Accepted Answer

Limestone rock surface (macro). Limestone is made mostly from the compressed skeletal remains of ancient marine life like coral and shellfish, so a block of limestone is essentially a graveyard of sea creatures fossilised millions of years ago.

Answer: Limestone rock surface (macro)

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