Which term describes visible shadow-like lines in a diamond caused by irregularities in the crystal structure?

Which term describes visible shadow-like lines in a diamond caused by irregularities in the crystal structure?

• A. Grain lines
• B. Habit
• C. Macle
• D. Twinned crystal

Answer: (A)

Grain lines describe the visible shadow-like lines you can see in a diamond that come from irregularities in how the crystal grew. As diamonds form, the internal lattice can shift slightly or join growth phases in different directions, creating subtle misalignments along certain planes. When light passes through these areas, it may produce faint lines or shadows that are visible under magnification or specific lighting. These lines are about the internal growth structure, not cracks or surface blemishes. The other terms refer to different crystal phenomena: habit is the diamond’s typical external shape, macle is when two crystals are intergrown to form a single crystal, and a twinned crystal involves a mirrored lattice across a twin plane.

Grain lines describe the visible shadow-like lines you can see in a diamond that come from irregularities in how the crystal grew. As diamonds form, the internal lattice can shift slightly or join growth phases in different directions, creating subtle misalignments along certain planes. When light passes through these areas, it may produce faint lines or shadows that are visible under magnification or specific lighting. These lines are about the internal growth structure, not cracks or surface blemishes. The other terms refer to different crystal phenomena: habit is the diamond’s typical external shape, macle is when two crystals are intergrown to form a single crystal, and a twinned crystal involves a mirrored lattice across a twin plane.