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

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

• A. Glassie
• B. Glide plane
• C. Graining (grain lines)
• D. Gravity sorting

Answer: (C)

Graining, or grain lines, refers to the visible shadow-like lines you can sometimes see inside a diamond. These lines come from irregularities in the crystal structure—basically how the crystal grew and where growth directions changed or interruptions occurred. Light traveling through the stone interacts with these internal grain boundaries, causing subtle shadowy lines that become visible at certain angles or under particular lighting. They aren’t cracks or flaws in the sense of damage; they’re natural features of the diamond’s crystal lattice and reflect its geological history. Other terms point to different ideas—glide plane is a crystallography term about symmetry, gravity sorting is a processing method, and a nonstandard term like glassie doesn’t describe this phenomenon—so the familiar name for this optical feature is graining.

Graining, or grain lines, refers to the visible shadow-like lines you can sometimes see inside a diamond. These lines come from irregularities in the crystal structure—basically how the crystal grew and where growth directions changed or interruptions occurred. Light traveling through the stone interacts with these internal grain boundaries, causing subtle shadowy lines that become visible at certain angles or under particular lighting. They aren’t cracks or flaws in the sense of damage; they’re natural features of the diamond’s crystal lattice and reflect its geological history. Other terms point to different ideas—glide plane is a crystallography term about symmetry, gravity sorting is a processing method, and a nonstandard term like glassie doesn’t describe this phenomenon—so the familiar name for this optical feature is graining.