Here's why:

* Foliation: This refers to the arrangement of mineral grains in a parallel or planar fashion. It happens when rocks are subjected to intense heat and pressure during metamorphism.

* Uneven Layers: The uneven layers in foliated rocks are formed because different minerals react differently to these extreme conditions. Some minerals may be more easily deformed or reoriented than others. This results in distinct bands or layers of mineral concentration.

Examples of foliated metamorphic rocks:

* Schist: Often has a shiny, flaky appearance due to the presence of mica minerals.

* Gneiss: Displays distinct banding with alternating light and dark layers.

* Slate: Fine-grained and usually breaks along parallel planes.

Important Note: While these rocks have uneven layers, they are not the same as sedimentary rocks, which are formed by the accumulation and cementation of sediments.