What is the habit of gem quality diamond?

The habit of gem quality diamond is primarily octahedral. This means that individual diamond crystals typically form in a distinct octahedron shape, characterized by its eight triangular faces. The octahedral shape is a result of the arrangement of carbon atoms in diamonds, which is structured in a face-centered cubic lattice. This unique crystallographic structure not only contributes to the diamond's hardness but also influences its spectacular brilliance and fire when cut properly.

While diamonds can also form in other habits, such as cubes or aggregates, these forms are less common for gem-quality diamonds. The cube shape can occur, but it is less visually appealing as a gem. Aggregates represent clusters of smaller diamond crystals fused together, which is not ideal for the individual, singular beauty associated with gem-quality stones. Therefore, the octahedral habit is integral to the gemological characteristics that define diamond quality.