Which term refers to a well-shaped, transparent octahedral diamond crystal with sharp, square edges?

• A. Crystal Shape (form)
• B. Crystalline
• C. Glassie
• D. Glide Plane

Answer: (C)

In gemology, the external geometry of a diamond crystal is described by its crystal form (also called crystal shape or habit). An octahedral diamond that is well formed with sharp, square edges is a clear example of its crystal form. The term that fits this description is Crystal Shape (form) because it names the visible shape of the crystal itself. The word crystalline refers to the material’s internal atomic arrangement, not the specific external shape. Glide plane is a symmetry element in crystal structures, not a descriptor of the diamond’s appearance, and terms like glassy describe surface texture rather than crystal habit. So the best term is Crystal Shape (form).