Colorless HPHT lab-grown diamonds are typically which type?

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

Answer: (A)

The key idea is how nitrogen content defines diamond types. Colorless HPHT lab-grown diamonds are typically Type IIa because they have little to no measurable nitrogen in the lattice. Nitrogen atoms in diamonds usually cause yellow or brown tints when present in various configurations, which is why Type Ia and Type Ib natural diamonds—those with noticeable nitrogen—often show color. Type IIa diamonds, on the other hand, lack detectable nitrogen, so they can be colorless or nearly colorless. There’s another type, IIb, that contains boron and appears blue and is electrically conductive, not colorless, so it doesn’t describe colorless HPHT stones. The HPHT growth environment commonly yields stones with minimal nitrogen incorporation, making Type IIa the typical classification for colorless lab-grown diamonds.