Foliated rock
The type of metamorphic rock that has flat layers is called "foliated metamorphic rock." Foliation occurs when pressure causes the minerals in the rock to align in parallel layers or bands. Examples of foliated metamorphic rocks include schist, slate, and gneiss. These layered structures result from the rearrangement of minerals under heat and pressure.
It is likely a type of metamorphic rock, such as schist or gneiss, which form under high temperature and pressure conditions leading to the alignment of mineral grains into flat layers.
Foliated rock has parallel layers.
slateschist
Sedimentary rocks have flat layers.
That would be sedimentary rock, and (honorable mention) occasionally metamorphic rock.
Rase
Foliated.
schist
Those would be non-foliated metamorphic rocks, like quartzite and marble.
Non-foliated metamorphic rock, such as marble or quartzite, is characterized by the absence of visible layering or banding. The mineral grains in these rocks recrystallize and grow in a uniform manner, without forming distinct layers like in foliated rocks. This type of metamorphism typically occurs under conditions of high pressure and temperature without the presence of directed stress.
A metamorphic rock.