Diamond type is determined by what?

• A. Diamond type is determined solely by color.
• B. The presence or absence of absorption caused by boron and/or nitrogen within a diamond's infrared spectrum—and whether the nitrogen is isolated or aggregated—determines its diamond type.
• C. Diamond type is determined by cut grade.
• D. Diamond type is determined by fluorescence.

Answer: (B)

The type of a diamond is determined by its impurities and how those impurities are arranged in the crystal, and we detect this by the infrared absorption pattern. Nitrogen can be present as isolated atoms or in aggregates (pairs or clusters), and boron can be present as well. The specific absorption features in the infrared spectrum reveal whether nitrogen is isolated or aggregated and whether boron is present, which together define the diamond’s type. That’s why this concept is about impurity content and aggregation, not just color, cut, or fluorescence. For example, isolated nitrogen gives one set of signatures (Type Ib), aggregated nitrogen gives another (Type Ia), no detectable nitrogen but possible boron gives Type IIb, and no detectable nitrogen or boron gives Type IIa.