Here's why:

* Sedimentary rocks are formed from the accumulation and cementation of sediments, which are fragments of other rocks, mineral grains, or organic matter.

* Shale is formed from the compaction of fine-grained clay and silt sediments.

* Sandstone is formed from the cementation of sand grains.

* Limestone is formed from the accumulation and cementation of calcium carbonate shells and other marine organisms.