Question

A rock that has many layers, is flat, and comes apart easily is most likely which type?

Answer 1

Sedimentary rock most likely, and a shale would be my best guess.

Explanation:

Sedimentary rocks that have a lot of clay minerals in them, like shale or siltstone, tend to split easily along bedding plans because of these same clay minerals (pic 2). These rocks are also good for hunting for fossils as the layers split easily, often revealing a well preserved fossil. See pic 1.

Some metamorphic rocks, like slate, phyllite, or schist, are also easily split as they were once shales themselves.