What are the only internal inclusions an HPHT lab-grown diamond may contain?

• A. Gas bubbles.
• B. Remnants of the metal catalyst it grew in.
• C. Natural mineral inclusions.
• D. Crystallographic defects.

Answer: (B)

In HPHT growth, a metal catalyst solvent is essential to dissolve carbon and drive diamond formation. Because the growth occurs in a metal-rich environment, tiny amounts of that metal can become trapped inside the crystal as inclusions. Those metallic remnants are characteristic of HPHT diamonds. Gas bubbles are not typical internal inclusions for HPHT stones, natural mineral inclusions come from diamonds formed in the Earth, and crystallographic defects are lattice irregularities rather than inclusions. So the expected internal inclusions you’d find in an HPHT lab-grown diamond are remnants of the metal catalyst it grew in.