Which characteristic describes foliated metamorphic rocks?

• A. Minerals are aligned in layers.
• B. They are formed by deposition of sediment.
• C. They have a glassy texture when cooled rapidly.
• D. They occur only near the surface.

Answer: (A)

Foliation in metamorphic rocks arises when rocks are subjected to directed pressure, causing mineral grains—especially flaky or platy minerals like mica—to rotate, flatten, and re-crystallize in a common orientation. This creates a planar, layered or banded texture as minerals align parallel to each other, giving the rock a striped appearance. That alignment and layering is what most clearly distinguishes foliated metamorphic rocks such as slate, phyllite, schist, and gneiss from other rock types.

The other descriptions don’t fit foliated metamorphic rocks: deposition of sediment forms sedimentary rocks, not metamorphic ones; a glassy texture results from rapid cooling of molten rock, typical of some igneous rocks; and metamorphic rocks can form at various depths and aren’t restricted to near the surface.