Shale is a sedimentary rock that can be metamorphosed into slate by heat and pressure.

Here's why:

* Heat: As shale is buried deeper in the Earth, it gets exposed to higher temperatures. This heat causes the clay minerals in shale to recrystallize and become more tightly packed.

* Pressure: The weight of overlying rock layers also exerts immense pressure on shale. This pressure helps to align the newly formed minerals in a parallel arrangement.

The combination of heat and pressure leads to the formation of slate, a metamorphic rock that exhibits a distinctive layered or foliated texture.