The internal directions parallel to the surfaces of a mineral's unit cell are referred to as what?

The internal directions parallel to the surfaces of a mineral's unit cell are referred to as what?

• A. Crystal Shape
• B. Glassie
• C. Glide Plane
• D. Crystal Planes

Answer: (D)

The main idea here is how crystals organize inside the lattice: flat, repeating layers that run through the structure are called crystal planes. These planes are parallel to the faces (surfaces) of the unit cell, so the directions that lie parallel to those surfaces are described by crystal planes. They define the orientation of the internal layers within the crystal and are identified by Miller indices, giving a precise way to reference each set of parallel planes. The other terms don’t fit because crystal shape refers to external form, glide plane is a symmetry element involving reflection and translation, and the misspelled term isn’t a standard crystallography concept.

The main idea here is how crystals organize inside the lattice: flat, repeating layers that run through the structure are called crystal planes. These planes are parallel to the faces (surfaces) of the unit cell, so the directions that lie parallel to those surfaces are described by crystal planes. They define the orientation of the internal layers within the crystal and are identified by Miller indices, giving a precise way to reference each set of parallel planes. The other terms don’t fit because crystal shape refers to external form, glide plane is a symmetry element involving reflection and translation, and the misspelled term isn’t a standard crystallography concept.