Which term refers to a flat, triangular twinned diamond crystal?

Which term refers to a flat, triangular twinned diamond crystal?

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

Answer: (C)

Twinning in diamonds can produce a distinct flat, triangular form that is recognized as a macle. A macle is specifically a twin of diamond crystal structure where two (or more) segments share a plane, giving a single crystal that looks flat and triangular. This is why macle is the right term: it names this particular twinned form, rather than the general habit (the usual growth shape of a diamond) or a vague “twinned crystal” (which could describe many different twinning combos). Grain lines describe internal seams in polycrystalline material, which isn’t about a single crystal’s shape, so they don’t fit either.

Twinning in diamonds can produce a distinct flat, triangular form that is recognized as a macle. A macle is specifically a twin of diamond crystal structure where two (or more) segments share a plane, giving a single crystal that looks flat and triangular. This is why macle is the right term: it names this particular twinned form, rather than the general habit (the usual growth shape of a diamond) or a vague “twinned crystal” (which could describe many different twinning combos). Grain lines describe internal seams in polycrystalline material, which isn’t about a single crystal’s shape, so they don’t fit either.