The hard shells of living things produce some kinds of limestone. How dopes limestone form? Limestone forms in the ocean, many living things, including coral, clams, oysters,
… and snails, have shells or skeletons made of calcite. There shells pile up as sediments on the ocean floor. It turns into calcite cement after millions of years which pieces together forming limestone. Limestone is also known as chalk. .
Over time coral buried by sediments will form into limestone (like the animal shells). .
And then get processed in a quarry and used by us (MORE)