I think old oysters become rock-like and sediment while new oysters grow on top of them. "3. In the wild, oysters set on (or attach to) old oyster shells. Whe

I think old oysters become rock-like and sediment while new oysters grow on top of them. "3. In the wild, oysters set on (or attach to) old oyster shells. When oysters grow in the wild in oyster reefs, they typically attach to old oyster shells (for the calcium carbonate — see above). Because of this they tend to grow in clusters and one on top of the other. This is also why wild oysters typically have “gnarly shapes,” says Chris, instead of the nice round shape and deep cup you associate with farmed oysters." https://www.thekitchn.com/island-creek-oysters-grower-tour-192689 https://www.thekitchn.com/island-creek-oysters-grower-tour-1...