They have been slowly recycled over millions of years.This is called the rock cycle.Sedimentary rocks form when tiny particles of rock that have been weathered and eroded settle out of slow moving ...

As the layers of sediment build up on top of one another ... has been continuously formed and recycled into other types of rock in a process called the “rock cycle.” This makes the rock record ...

"Sedimentary rocks are principally composed ... recycled and transformed by geological processes is known as the rock cycle. Some rocks are mono-mineralic, meaning they only contain one mineral.