What is the foundation of the diamond type classification system?

• A. The presence or absence of nitrogen and boron atoms and how they are arranged in the crystal lattice.
• B. Color and fluorescence characteristics.
• C. Crystal symmetry and lattice type.
• D. Carat weight and cut quality.

Answer: (A)

The foundation of diamond type classification is the chemical impurities and how they occupy the crystal lattice, specifically nitrogen and boron and the way nitrogen is arranged. Diamonds are grouped by whether nitrogen is present or absent, and if present, whether it appears as isolated atoms or as aggregates, which leads to Type Ib, Type Ia, and Type II variants. Type Ia and Ib describe nitrogen-containing diamonds with different lattice arrangements, Type IIa diamonds have little to no detectable nitrogen, and Type IIb diamonds contain boron, which changes color and conductivity. This impurity-based framework explains why colors (like yellow from nitrogen or blue from boron) and lattice behavior determine the type, while other characteristics such as color or fluorescence, crystal symmetry, carat weight, or cut quality describe additional properties but do not define the classification basis.