Which term denotes the geometric shape of a well-formed crystal?

Which term denotes the geometric shape of a well-formed crystal?

• A. Crystal Axes
• B. Doubly Refractive (anisotropic)
• C. Glide Plane
• D. Crystal Shape (form)

Answer: (D)

Crystal form describes the external geometric shape of a well-formed crystal. It captures the overall silhouette defined by the crystal faces and their arrangement, which is exactly what we mean by the crystal’s shape. The other terms point to different ideas: crystal axes are the three directional lines in the lattice; anisotropic (doubly refractive) describes direction-dependent optical behavior, not shape; and a glide plane is a symmetry element combining reflection and translation, unrelated to the crystal’s external form. So the term that denotes the geometric shape is crystal form.

Crystal form describes the external geometric shape of a well-formed crystal. It captures the overall silhouette defined by the crystal faces and their arrangement, which is exactly what we mean by the crystal’s shape. The other terms point to different ideas: crystal axes are the three directional lines in the lattice; anisotropic (doubly refractive) describes direction-dependent optical behavior, not shape; and a glide plane is a symmetry element combining reflection and translation, unrelated to the crystal’s external form. So the term that denotes the geometric shape is crystal form.