Rock textures — foliation occurrence by rock class Foliated structure (planar alignment of minerals) is most commonly associated with which class of rocks?

Introduction / Context:
Foliation is a planar fabric resulting from differential stress that aligns platy or elongate minerals. Recognizing foliation helps engineers and geologists anticipate anisotropic behavior such as preferred failure planes and directional permeability.

Given Data / Assumptions:

• Foliation develops during solid-state deformation and metamorphism.
• Common foliated rocks: slate, phyllite, schist, gneiss.
• Sedimentary bedding is a different planar feature and should not be confused with foliation.

Concept / Approach:
Under regional metamorphism, pressure solution and recrystallization align mica and other minerals perpendicular to maximum compressive stress, producing foliation. Igneous rocks may show flow banding but that is not foliation; sedimentary rocks show bedding/lamination formed by deposition, not metamorphic alignment.

Step-by-Step Solution:
Define foliation: planar fabric from metamorphic processes.Map to rock class: metamorphic rocks commonly exhibit foliation.Exclude other classes: sedimentary → bedding; igneous → massive or flow structures.

Verification / Alternative check:
Field mapping uses foliation strike and dip to evaluate slope stability and excavation directions.

Why Other Options Are Wrong:
Sedimentary rocks have bedding, not foliation.

Igneous rocks are generally non-foliated; any banding is not metamorphic foliation.

“None of these” contradicts standard metamorphic petrology.

Common Pitfalls:
Confusing bedding cleavage with slaty cleavage; ignoring anisotropy in stability analysis; equating flow banding with foliation.

Final Answer:
Metamorphic rocks