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

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

• A. Macle
• B. Octahedron
• C. Point Defect
• D. Singly Refractive (Isotropic)

Answer: (A)

A macle is the term for a flat, triangular twinned diamond crystal. It forms when two crystal halves grow together along a shared twinning plane, producing a flat, triangular shape with a visible seam. This is different from the common crystal form of diamond (the octahedron), which is a regular, single-crystal shape with eight faces. A point defect refers to a missing or impurity atom in the lattice, not a macle’s flat twin geometry, and singly refractive (isotropic) describes how light would propagate in a material entirely uniform in all directions, which diamonds are not.

A macle is the term for a flat, triangular twinned diamond crystal. It forms when two crystal halves grow together along a shared twinning plane, producing a flat, triangular shape with a visible seam. This is different from the common crystal form of diamond (the octahedron), which is a regular, single-crystal shape with eight faces. A point defect refers to a missing or impurity atom in the lattice, not a macle’s flat twin geometry, and singly refractive (isotropic) describes how light would propagate in a material entirely uniform in all directions, which diamonds are not.