What is this close-up picture? (WotsThat: Agate geode banding)

Question

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

ApatiteBlue · Accepted Answer

Agate geode banding. Agate Geode Banding The vibrant stripes in agate geodes form so slowly that each band can take thousands of years to develop—meaning a geode the size of your fist might contain a timeline stretching back millions of years in just a few inches of stone. Even wilder: scientists can sometimes read these bands like tree rings to figure out what the ancient environment was like when each layer formed, including clues about temperature and mineral-rich water conditions from deep in Earth's past.

Answer: Agate geode banding

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