Specifically, they are often called sandstone if the primary component is sand, or coquina if the primary component is shells.

* Sandstone is formed from the cementation of sand grains, which are often the eroded remains of older rocks.

* Coquina is a type of limestone formed from cemented shell fragments.

However, it's important to note that many sedimentary rocks are mixtures of sand, shells, and other materials. These rocks may be given more descriptive names based on their specific composition, like "fossiliferous sandstone" or "shell-rich limestone."