"As Grown" vs "Post-Growth Treatment" on a Lab-Grown Diamond Report: What the Comment Means

The short answer: On an IGI laboratory-grown diamond report, "As Grown - No indication of post-growth treatment" means IGI found no sign that the diamond was treated after it came out of the growth chamber. "May include post-growth treatment" means it may have been, most often with a high-temperature anneal to improve its color. For fancy colors, "Indications of post-growth treatment" means IGI found evidence of treatment. The color and clarity grades describe the diamond as it is now either way. Whether "as grown" matters to you is a preference, not a quality grade.

You'll find this comment in the Comments section of the report, usually next to the growth method (CVD or HPHT) and sometimes a diamond type such as "Type IIa." Every stone we list links to its report, and this is one of the most useful lines on it.

What IGI changed in 2021

Before 2021, IGI's laboratory-grown reports carried a blanket statement that lab-grown diamonds "may include post-growth treatments to alter color." In January 2021, IGI announced that it had done the research and data collection to say more specifically whether a given diamond was "as grown" or may have been treated.

According to IGI's announcement:

  • For untreated CVD and HPHT diamonds, reports would name the growth process and state that the stone is "as grown with no indication of post-growth treatment."
  • For other CVD-created diamonds, reports would note that they "may include post-growth treatment."
  • Customers could also request that the diamond type be shown, such as type IIa for CVD and type II for HPHT diamonds.
  • IGI was working toward additional commentary on post-growth treatment for fancy-color diamonds.

Here's how the comment reads on a real IGI report for a 0.98 carat HPHT-grown emerald cut (report LG622495677):

As Grown - No indication of post-growth treatment. This Laboratory Grown Diamond was created by High Pressure High Temperature (HPHT) growth process. Type II

And on an IGI report for a Fancy Intense Pink CVD diamond:

This Laboratory Grown Diamond was created by Chemical Vapor Deposition (CVD) growth process. Indications of post-growth treatment.

The three wordings side by side

Comment on the report What it tells you Where you'll usually see it
As Grown - No indication of post-growth treatment IGI found no evidence of treatment after growth Some HPHT and some CVD white diamonds
May include post-growth treatment The diamond may have been treated after growth, usually to improve color Many CVD white diamonds
Indications of post-growth treatment IGI found evidence of treatment Fancy-color diamonds whose color was produced or changed after growth, such as many pinks

Reports issued before the 2021 change may carry the older blanket wording. If a report's comments don't match any of these, contact IGI or ask us before you buy, and we'll tell you what we know about that stone.

Why so many CVD diamonds are treated after growth

GIA's 2024 review of laboratory-grown diamonds submitted for grading explains the reason. Some CVD-grown diamonds come out of the reactor with a brown tint, caused by defects formed during growth. As with natural brown diamonds, a high-pressure, high-temperature (HPHT) treatment can reduce or remove that brown color. GIA notes that manufacturers can use fast-growth recipes even if they produce brown color, then improve the color grade with post-growth annealing, which may be faster, easier or cheaper than growing a colorless crystal directly.

How common is it? GIA reports that since 2020, approximately 80% of the CVD diamonds submitted to GIA have undergone post-growth processing. GIA notes that this reflects its own submissions, and global figures may differ.

Two clarifications from GIA help avoid confusion:

  • HPHT treatment isn't HPHT growth. The equipment can be similar, but HPHT treatment is a separate step done to an existing diamond. GIA notes it runs at higher temperatures than HPHT growth (above 1600°C) and doesn't add any diamond material.
  • Other annealing methods exist. GIA also describes low-pressure, high-temperature (LPHT) annealing under vacuum or inert gas as a way to change the color of CVD-grown diamonds.

HPHT-grown diamonds are a different story. GIA's 2017 review of HPHT-grown diamonds notes that colorless HPHT-grown diamonds are reportedly sold as grown, without post-growth color modification. That's why you'll often see "As Grown" on HPHT reports. Our guide to CVD vs HPHT lab-grown diamonds covers both processes.

Three common misreadings

  • "HPHT on the report means it was treated." No. "Created by High Pressure High Temperature (HPHT) growth process" describes how the diamond was grown. HPHT treatment is a separate step, most often applied to CVD-grown diamonds.
  • "No treatment wording means untreated." Not necessarily. Before 2021, IGI's reports used a blanket statement that lab-grown diamonds may include post-growth treatment. The wording that affirmatively says a stone is untreated is "As Grown - No indication of post-growth treatment."
  • "Treated means coated." The color treatment GIA describes for CVD diamonds is a high-temperature anneal that acts on defects inside the crystal, such as the vacancy clusters associated with brown color. It isn't a surface coating. Coatings are a different kind of treatment and aren't what this comment refers to.

Fancy colors: where treatment is the norm

For fancy colors, post-growth treatment is often what creates the color. GIA describes pink and red in CVD-grown diamonds being produced by a sequence of annealing, irradiation and a lower-temperature anneal that creates nitrogen-vacancy (NV) centers. By contrast, blue HPHT-grown diamonds usually get their color from boron added during growth. Our guide to pink, blue and other fancy-color lab-grown diamonds goes color by color.

Does "as grown" matter?

It depends on what you care about. Here's how to think about it honestly.

What the treatment comment doesn't change:

  • The grades. Color, clarity and polish and symmetry grades describe the diamond as submitted. A G VS1 is graded G VS1 whether or not it was annealed.
  • What it is. A treated laboratory-grown diamond is still diamond. Under the FTC's definition (16 CFR 23.12), diamond is a mineral of essentially pure carbon crystallized in the isometric system, with a hardness of 10.
  • What you see. Look at the stone's appearance in video and its measurements, as you would for any diamond.

What the comment does tell you:

  • The diamond's history. Some buyers want a stone that's untouched since growth, just as some buyers of mined gems prefer untreated stones. If that matters to you, filter for "As Grown" on the report.
  • Disclosure. The FTC's Jewelry Guides (16 CFR 23.24) treat it as deceptive to fail to disclose a gemstone treatment that isn't permanent, creates special care requirements, or significantly affects value. The report comment is the laboratory's own record of what it found, and it's the place to check.

We don't make claims that one is better than the other, and we don't make resale or investment claims about either.

How to check a stone on Carat Confidential

  1. Note the growth method on the listing. Every listing shows whether the stone is CVD- or HPHT-grown. Most stones in our catalog are CVD, and some are HPHT.
  2. Open the report from the listing. The verify link goes to the grading laboratory, where you can confirm the report number matches the stone. Most of our stones carry IGI reports and some carry GIA reports. Our IGI certification guide walks through an IGI report, and GIA vs IGI explains how GIA's lab-grown documents differ.
  3. Read the Comments section for the treatment wording and diamond type.
  4. Shortlist accordingly. If "As Grown" is a must, it narrows your choice. HPHT-grown stones are a natural place to start in the white diamonds collection, and you can browse by shape from round to emerald.
  5. Then choose on appearance: measurements, proportions and the 360° video. Our size chart and online buying checklist help with that step.

Our listings show the growth method; for the treatment wording, open the report. If you're comparing several stones and want help, contact us.

Frequently asked questions

What does "As Grown - No indication of post-growth treatment" mean? IGI examined the diamond and found no evidence that it was treated after growth. The phrase appears on reports for both CVD and HPHT diamonds.

What does "may include post-growth treatment" mean on an IGI report? The diamond may have been treated after growth, usually with high-temperature annealing to improve its color. IGI uses this wording for CVD diamonds that it doesn't describe as "as grown."

Are most CVD lab-grown diamonds treated? According to GIA, approximately 80% of the CVD diamonds submitted to GIA since 2020 have undergone post-growth processing, most commonly HPHT treatment to improve color.

Is an "as grown" lab diamond better? Not by grade. The color and clarity grades describe the stone as it is. "As grown" tells you about its history, which some buyers prefer. It's a personal choice.

What does "Type IIa" or "Type II" mean on the report? It's a scientific classification. GIA explains that type II diamonds contain no nitrogen detectable by infrared spectroscopy, and colorless laboratory-grown diamonds are type II. IGI lets the submitter request that the type be shown.

Sources

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