Which inclusion patterns might indicate a lab-grown diamond with HPHT origin?

• A. Metallic inclusions or flux, and certain color zoning or growth striations.
• B. Gas inclusions or feathering.
• C. Uniform diffusion of color throughout the stone.
• D. Absence of inclusions or color zoning.

Answer: (A)

Recognizing HPHT origin hinges on the type of inclusions left behind by the growth process. In HPHT lab-grown diamonds, metallic inclusions or flux residues are common because the growth uses metal catalysts and, at times, a flux. These metallic flecks or flux traces are distinctive clues inside the crystal. Along with them, color zoning or growth striations often appear, reflecting directional crystal growth under the HPHT conditions. Together, these features form a pattern that searchers use to identify HPHT origin.

Gas inclusions or feathering tend to be less diagnostic for HPHT origin and can appear in natural stones or other growth methods, so they’re not as strong an indicator. Uniform diffusion of color throughout is typically the result of a diffusion treatment rather than growth origin, and the absence of inclusions or color zoning would not point toward HPHT specifically.