What is this picture?

Question

What is shown in this image?

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