From Lab to IGI Certificate: How a Lab Grown Diamond Gets Graded After Growth

A lab grown diamond receives its IGI grading report after a structured sequence of steps: origin screening using advanced spectroscopy, independent 4Cs assessment by trained gemologists under controlled conditions, and a permanent laser inscription that ties the physical stone to its paper record. That process is the same whether the diamond was grown by CVD or HPHT, and it produces the same full D-to-Z color and FL-to-I3 clarity grades used for natural diamonds.

Understanding that sequence matters because the certificate is not a seller’s description. It is an independent document issued before the stone reaches any retailer, and every grade on it was set by people who never knew whose diamond they were evaluating.

What happens the moment a diamond arrives at the IGI lab?

The first thing IGI does is screen the stone to confirm what it actually is. Using spectroscopic analysis and optical testing, gemologists establish whether the diamond is natural, laboratory-grown, or a simulant. For lab grown diamonds, this screening also identifies the growth method: either High Pressure High Temperature (HPHT) or Chemical Vapor Deposition (CVD). That distinction gets recorded in the Comments section of the final report.

This step is not a formality. A polished lab grown diamond and a polished natural diamond are chemically and optically identical, so visual inspection alone cannot separate them. The spectroscopic equipment IGI uses detects growth patterns, trace element signatures, and fluorescence characteristics that are specific to each origin type. Only after that origin is confirmed does the stone move forward in the grading queue.

Each diamond also receives an internal identification number on arrival. Graders never see owner information, and the stone returns to central control between stages, so the gemologists who examine it at each step are effectively randomized. That structure reduces the chance of any single grader’s judgment skewing the final result.

How does IGI evaluate the 4Cs for a lab grown diamond?

Grading begins with carat weight. IGI’s scales are calibrated to four decimal places, so a stone recorded as 1.00 ct is not an approximation.

Color comes next. The diamond is placed upside down in a standardized viewing environment and assessed against master comparison stones on the D-to-Z scale. Viewing the stone from the side rather than face-up removes the visual interference of brilliance, which would otherwise make color harder to read accurately.

Clarity is assessed at 10x magnification. The grader evaluates the visibility, size, number, location, and nature of any internal characteristics or surface blemishes. Lab grown diamonds can carry inclusions just as natural diamonds do, though the type sometimes differs by growth method: CVD stones may show faint graining or cloud-like formations, while HPHT stones occasionally contain traces of the metallic flux used during growth. Whatever is present gets mapped into a clarity diagram on the report.

Cut grading works differently depending on shape. For round brilliants, IGI compares the stone’s proportions against its own brightness, fire, and scintillation research to arrive at an overall cut grade. Fancy shapes, such as radiant, emerald, or pear cuts, go through a four-step system that combines polish and symmetry assessment, proportions qualification, shape-specific requirements, and light-return grading. A fancy shape must pass all four steps to earn an Excellent cut grade.

Beyond the 4Cs, the finished report includes the stone’s shape and measurements, a fluorescence grade, polish and symmetry grades, the growth method notation, and a clarity plot showing the location of any characteristics.

What is the laser inscription, and why does it matter?

After grading is complete, IGI inscribes the report number on the diamond’s girdle using a fine laser beam. The girdle is the thin outer edge of the stone, the band between the crown and the pavilion. The inscription is microscopic: invisible to the naked eye but readable under a 10x jeweler’s loupe. For lab grown diamonds, the inscription also includes the words “LAB GROWN” alongside the report number.

The purpose is straightforward. A paper certificate proves a diamond was graded. The laser inscription proves that your specific diamond is the one that was graded. Without it, a stone could in theory be swapped for a different one while the certificate stayed the same. With it, any buyer or jeweler can check the girdle, read the number, and confirm it matches the report exactly. IGI’s online verification tool at igi.org lets anyone cross-reference that number against the full grading record in under a minute.

How does IGI’s approach differ from GIA’s for lab grown diamonds in 2026?

This is worth knowing before you shop. In October 2025, GIA replaced full 4Cs grading for lab grown diamonds with a simplified two-tier system that classifies stones as either “Premium” or “Standard” rather than assigning specific grades like D color or VVS2 clarity. IGI, by contrast, continues to issue full 4Cs reports for lab grown diamonds on the same D-to-Z color scale and FL-to-I3 clarity scale it applies to natural diamonds. For a buyer comparing two stones or trying to understand exactly what they are paying for, that specificity is practically useful in ways that a two-tier label is not.

The Certificate Is the Last Step of the Diamond’s Journey

Growing a lab diamond takes weeks in a controlled chamber. Cutting and polishing it takes skilled hands and careful planning. But the IGI grading report is what converts all of that into documented, verifiable information a buyer can actually use.

The grading process covers origin confirmation, independent 4Cs assessment, and a laser inscription that permanently links the stone to its record. Every grade was set under standardized conditions by gemologists who had no financial stake in the outcome. That independence is the point.

If you want to see what that looks like in practice, Ouros Jewels includes a full IGI grading report with every lab grown diamond, including the GIA & IGI Certified Lab Grown Diamonds available in the certified collection. The report number, the clarity plot, the growth method notation: all of it is there before the stone reaches you.

Frequently Asked Questions

Does the growth method listed on an IGI report (CVD or HPHT) affect the diamond’s quality?

Neither CVD nor HPHT produces a superior diamond in terms of optical performance or durability. Both methods grow stones that are chemically and physically identical to mined diamonds. The growth method notation on the report is a transparency disclosure, not a quality indicator, and neither designation should raise or lower a stone’s appeal.

Can IGI detect whether a lab grown diamond has been post-growth treated?

Yes. IGI’s spectroscopic screening can identify post-growth HPHT treatment applied to CVD diamonds, a process sometimes used to improve color. When treatment is detected, IGI notes it in the Comments section of the report. Buyers should look for the word “untreated” in that section when it matters to them.

Is an IGI card certificate the same as a full IGI grading report for a lab grown diamond?

No. A card certificate covers only the basic 4Cs and the inscription number, with no proportions data, no clarity plot, and no treatment disclosure. A full IGI grading report includes all of those fields. When comparing diamonds from different retailers, confirm which format you are receiving, since the two documents contain meaningfully different levels of detail.

How long does the IGI grading process typically take for a lab grown diamond?

Turnaround time varies by lab location and submission volume, but IGI is generally recognized in the trade for faster processing of lab grown diamonds compared to some other certification bodies. Most standard submissions are completed within a few business days to a couple of weeks, depending on the service level selected by the submitting jeweler or manufacturer.

What does the clarity diagram on an IGI report actually show?

The clarity diagram is a schematic drawing of the diamond that maps the location, type, and approximate size of any internal characteristics (inclusions) or surface blemishes (blemishes). It uses standardized symbols: a red mark typically indicates an internal feature, a green mark a surface one. The diagram lets you see where inclusions sit relative to the table and whether they fall in positions that affect visible brilliance.