CVD vs HPHT Lab-Grown Diamonds: How They're Made and Whether It Matters

The short answer: CVD (chemical vapor deposition) and HPHT (high pressure, high temperature) are the two main ways laboratory-grown diamonds are made. Both produce diamond, with the same crystal structure and essentially the same physical and optical properties as a mined diamond. Neither method guarantees a better stone. A well-cut, eye-clean diamond can come from either process, and so can a poor one. Judge the individual diamond by its grading report, its measurements and how it looks.

Each of our listings states the growth method in the specifications table, and you can confirm it in the grading report's comments. Most of our stones are CVD-grown and some are HPHT. Here's what those labels mean.

How HPHT diamonds are grown

HPHT is the older method. GIA describes it as a process that recreates the extreme heat and pressure found deep in the earth, where natural diamonds form:

  • A small diamond seed is placed in a specially designed press.
  • The growth chamber is heated to about 1,300–1,600 °C, at pressures above 870,000 pounds per square inch.
  • A molten metal flux (metals such as iron, nickel or cobalt) dissolves a high-purity carbon source.
  • Carbon atoms crystallize on the seed, and a diamond crystal grows over days to weeks.
  • The crystal is then cut and polished like any other diamond.

GIA notes that HPHT crystals typically grow with both cubic and octahedral faces, a different shape from most natural crystals. Growing colorless HPHT diamonds was once difficult because nitrogen turns diamond yellow, but GIA reports that advances have made large colorless HPHT stones possible. Adding boron during growth produces blue crystals.

How CVD diamonds are grown

CVD is the newer method and runs at lower pressure. According to GIA:

  • Thin diamond seed plates are placed in a vacuum chamber.
  • The chamber is filled with a carbon-containing gas (typically methane with hydrogen) and heated to about 900–1,200 °C.
  • A microwave beam breaks the gas down into a plasma, and carbon deposits onto the seeds, building the crystal layer by layer.
  • The diamonds are taken out every few days so the top surface can be polished before growth continues. A batch can take three or four weeks.

GIA also notes that CVD requires lower upfront equipment costs than HPHT but "may require subsequent treatment to improve the color." That leads to the most practical question for buyers.

Post-growth treatment: the part that actually shows up on the report

Many CVD crystals come out of the chamber with a brownish tint. In its overview of growth processes, GIA wrote that most colorless CVD material on the market had probably been brown crystals that were decolorized by HPHT annealing (a heat treatment). In other words, a stone can be CVD-grown and still have been through HPHT treatment. These are two different uses of the same letters.

Grading labs disclose what they find (see what an IGI report records and how to verify it). IGI has explained that its laboratory-grown reports state the growth process. Untreated CVD and HPHT stones are described as "as grown with no indication of post-growth treatment", and other CVD stones are noted as ones that "may include post-growth treatment." Look for this wording in the comments section of the report.

Treatment is also common in color. GIA notes that colors such as pink and red can be produced by post-growth processes involving radiation and heating. If a fancy-color stone's report mentions treatment, that's the lab telling you how the color came about. It isn't a hidden flaw.

How labs tell CVD, HPHT and mined diamonds apart

You can't tell the growth method (or mined vs laboratory-grown) by eye. GIA uses growth-related clues and advanced instruments. It summarizes typical features like this:

Feature (typical, not universal) HPHT-grown CVD-grown
Color distribution Can be uneven, sometimes geometric zoning Usually even
Inclusions Metallic flux inclusions Occasional dark pinpoint (e.g., graphite) inclusions; no metallic ones
Strain under crossed polarizers None or weak Banded strain patterns
Fluorescence pattern Often cross-shaped Can show striations
Phosphorescence Occasional Occasional

GIA uses a fluorescence imaging instrument called the DiamondView to see these growth patterns. Concentric patterns point to natural origin, cross-shaped patterns to HPHT and striations to CVD. GIA also notes that not every stone shows every feature, which is why identification belongs in a laboratory. That's another reason to buy a stone with an independent report.

One practical point from GIA's table: some HPHT stones contain enough metallic flux that a strong magnet can pick them up. That's a curiosity, not a quality grade, and it doesn't make the stone any less a diamond.

So which is better?

Neither, as a category. What matters is the stone in front of you:

  • Cut (for rounds, the lab's cut grade; for all shapes, polish, symmetry and proportions) drives how the stone handles light.
  • Color and clarity tell you how white and how clean the stone is. The 360° video shows whether any inclusions are visible.
  • Measurements tell you how big it will look face-up.
  • The report comments tell you the growth method and whether post-growth treatment is indicated.

If you have a personal preference, such as wanting an as-grown stone or wanting to avoid treated color, that's a valid choice. Make it by reading the report comments, not from the letters CVD or HPHT alone.

Where the growth method matters most: fancy colors

For colorless stones, CVD and HPHT diamonds can end up looking the same. For fancy colors, the method and any treatment explain where the color comes from. GIA notes that boron produces blue during HPHT growth, while pinks and reds are often the result of post-growth treatment. If you're shopping for blue diamonds, pink diamonds or anything else in our fancy-color collection, read the report comments before you choose.

Shopping by growth method with us

Every product page lists the growth method in the specifications table, next to the grading lab and report number. To compare, start with a shape you like, such as round or oval, or browse all diamonds. Then:

  1. check the growth method in the specifications;
  2. open the report link and read the comments for treatment wording;
  3. compare cut, color, clarity and measurements across stones;
  4. watch the 360° video where one is available.

Our FAQ also covers the 4Cs and how to verify a report.

Related reading: IGI-Certified Lab-Grown Diamonds: What IGI Certification Means and How to Verify a Report · Laboratory-Grown vs. Natural Diamonds: What's the Same and What's Different

FAQ

Are CVD diamonds real diamonds? Yes. CVD and HPHT both produce diamond: carbon crystallized in the cubic (isometric) system, which is how the FTC's Jewelry Guides define a diamond. Under those guides the origin must be disclosed, which is why it's called laboratory-grown.

Is HPHT better than CVD? Not as a rule. Each process can produce excellent or mediocre stones. Compare the individual diamonds' grades, measurements and appearance.

Can a CVD diamond also be HPHT-treated? Yes. HPHT can refer to a growth method or to a post-growth heat treatment. GIA says that many colorless CVD stones were decolorized by HPHT annealing. The report's comments tell you what applies to your stone.

Can a jeweler tell whether my diamond is CVD or HPHT? Not reliably by eye. Separating growth methods usually takes laboratory instruments such as fluorescence imaging. The grading report and the laser inscription on the girdle are your practical records.

Are HPHT diamonds magnetic? Some are, slightly. GIA notes that HPHT-grown diamonds with larger metallic flux inclusions can sometimes be picked up with a magnet. It says nothing about beauty or quality, and CVD diamonds don't contain those metallic inclusions.

Does the report mention treatments? Yes. IGI says its laboratory-grown reports indicate whether a stone is as grown or may include post-growth treatment. For fancy colors, IGI says permanent treatments are noted in the comments and that it doesn't issue full grading reports for diamonds with non-permanent treatments.

Sources

Reviewed September 2026 against the sources above.

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