Here's why:

* Foliation refers to the parallel alignment of minerals within a rock, giving it a layered or banded appearance. This occurs when the rock is subjected to intense pressure and heat, causing the minerals to re-crystallize and align themselves perpendicular to the stress.

* Non-foliated metamorphic rocks lack this layered structure. They typically form when the pressure is more evenly distributed, or the minerals are more resistant to alignment.

Examples of foliated metamorphic rocks include slate, schist, and gneiss. Examples of non-foliated metamorphic rocks include marble, quartzite, and hornfels.

Therefore, the same type of rock can be both foliated and non-foliated depending on the specific conditions of its formation.