The habit of a gem-quality diamond is the...

The habit of a gem-quality diamond is the...

• A. Cube
• B. Dodecahedron
• C. Tetrahedron
• D. Octahedron

Answer: (D)

Crystal habit is about the shape a crystal tends to grow into, shaped by its internal lattice. Diamonds have a cubic lattice, and the most well-formed, lowest-energy faces are the triangular faces on the {111} planes. When a diamond crystal grows without external restraints, these faces come together to form an octahedron, which is the classic external form for gem‑quality diamonds. Other shapes like a cube or dodecahedron can occur in some minerals or under special conditions, but they are not the typical diamond habit because their faces aren’t the most prominent in natural growth.

Crystal habit is about the shape a crystal tends to grow into, shaped by its internal lattice. Diamonds have a cubic lattice, and the most well-formed, lowest-energy faces are the triangular faces on the {111} planes. When a diamond crystal grows without external restraints, these faces come together to form an octahedron, which is the classic external form for gem‑quality diamonds. Other shapes like a cube or dodecahedron can occur in some minerals or under special conditions, but they are not the typical diamond habit because their faces aren’t the most prominent in natural growth.