What type is the majority of CVD lab-grown diamonds?

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

Answer: (A)

Diamonds are categorized by impurities, especially nitrogen and boron. Type IIa means essentially no detectable nitrogen or boron, while Type Ia and Ib contain nitrogen, and Type IIb contains boron that gives blue color. In typical CVD growth, the environment is optimized to minimize nitrogen incorporation, so most crystals form with very little nitrogen, landing in the Type IIa category. That’s why the majority of CVD lab-grown diamonds are Type IIa—not because they’re forced to be a certain color, but because the growth conditions naturally produce nitrogen-free crystals. Boron-doped Type IIb diamonds are possible but much less common in standard CVD processes, and the nitrogen-rich types Ia and Ib are more associated with natural diamond formation.