Most diamond screening devices are based on the fact that the majority of natural diamonds are which type?

• A. Type Ib
• B. Type IIa
• C. Type IIb
• D. Type Ia

Answer: (D)

Diamond screening devices rely on a feature that’s common in natural stones: the presence and form of nitrogen impurities. Diamonds are classified as Type I or Type II based on nitrogen content, with Type I containing nitrogen and Type II having little to none. Within Type I, nitrogen is typically present in aggregated forms (A centers and B centers), which is the form known as Type Ia. This Type Ia pattern is by far the most prevalent in natural diamonds, so screening tools are designed to detect nitrogen-related signals—such as particular absorption and fluorescence characteristics—that most natural diamonds exhibit. While other types (like those with isolated single nitrogen atoms or boron-related impurities) exist, they are far less common, so the reliance on nitrogen features reflects the typical natural-diamond profile.