CVD vs HPHT: The Two Ways to Grow a Diamond

If you look closely at a lab grown diamond certificate or product specifications, you might notice two abbreviations: CVD and HPHT. They represent two different growth technologies, and they are key to understanding a diamond's "origin."

HPHT (High Pressure High Temperature) is the earliest method used to produce gem-quality lab grown diamonds. It simulates the underground conditions where natural diamonds form: a carbon source (usually graphite) and a metal catalyst are placed in a reactor, subjected to 5–6 GPa of pressure and temperatures of 1300–1600°C, allowing carbon atoms to crystallize on a diamond seed. HPHT grows relatively fast, producing a crystal in a few days to a few weeks.

CVD (Chemical Vapor Deposition) takes a different path. It doesn't require such high pressure. Instead, carbon-containing gases (like methane) are introduced into a vacuum chamber, activated by microwaves to create plasma, and carbon atoms are deposited layer by layer onto a diamond seed, "printing" a diamond layer by layer. The CVD growth cycle usually takes longer, sometimes several weeks.

Neither method is inherently "better" than the other. The key lies in post-growth treatment. Many CVD diamonds have a brownish tint after growth and require subsequent HPHT treatment to improve their color to a colorless grade. According to GIA data, about 80% of CVD diamonds submitted after 2020 have undergone annealing treatment.

What does this mean for you as a buyer? The technology itself doesn't determine quality; the certificate does. Regardless of whether a diamond is CVD or HPHT grown, its final color, clarity, and cut grades are independently evaluated by labs like IGI. You don't need to obsess over "how it was made"—you just need to read the certificate.