Everything you need to know before buying a certified lab diamond in Canada.
Lab-grown diamonds have become one of the most popular choices for engagement rings and for good reason. They share the same physical, chemical, and optical properties as mined diamonds, often at a significantly lower price point. But a question we hear constantly at Jacob Mercari is: "How do I know I'm getting a quality stone?"
The answer comes down to grading and certification. A certified diamond lab-grown or natural has been independently evaluated by a gemological laboratory and issued a report detailing its characteristics. Understanding what that report means is the difference between buying with confidence and buying blind.
Here's exactly how lab-grown diamonds are graded, which certifications matter, and what to look for when reviewing a diamond report.
Are Lab-Grown Diamonds Graded the Same Way as Natural Diamonds?
Yes, with one important clarification. Lab-grown diamonds are graded using the exact same criteria as mined diamonds: the internationally recognized 4Cs developed by the Gemological Institute of America (GIA). The grading process, the standards, and the certificate format are essentially identical.
The only difference is disclosure. Reputable grading labs will clearly note on the certificate that the diamond was laboratory-grown, and they may also indicate the growth method used either Chemical Vapour Deposition (CVD) or High Pressure High Temperature (HPHT).
This transparency is important. It protects the buyer and ensures you know exactly what you're purchasing.
The 4Cs: How Lab Diamonds Are Evaluated
Whether you're looking at a natural mined diamond or a lab-grown stone, graders assess quality across four dimensions:
1. Cut
Cut is the most critical factor affecting a diamond's beauty. It refers to how well the stone has been shaped and faceted not the shape itself (round, oval, princess, etc.), but the precision of the angles, proportions, and symmetry.
A well-cut lab diamond will maximize light return, producing the brilliance and fire that make diamonds so visually striking. Grading labs assign cut grades ranging from Excellent/Ideal to Poor.
2. Colour
Diamond colour is graded on a scale from D (completely colourless) to Z (noticeable yellow or brown tint). The closer to D, the rarer and more valuable the stone.
Lab-grown diamonds span the full colour range, though colourless and near-colourless stones (D–J) are the most commonly selected for engagement rings. One advantage of lab diamonds: producing colourless stones is more predictable in a controlled environment, meaning high-colour grades are more accessible at lower price points than their mined counterparts.
3. Clarity
Clarity describes the presence of internal characteristics (inclusions) and surface blemishes. The GIA clarity scale runs from Flawless (FL) no inclusions visible under 10x magnification down to Included (I1, I2, I3), where flaws may be visible to the naked eye.
Lab-grown diamonds can have inclusions just like natural diamonds, though the nature of those inclusions may differ based on growth method. CVD diamonds may show graining or cloud-like formations; HPHT diamonds may contain metallic flux inclusions. A reputable grading report will identify any significant characteristics.
4. Carat Weight
Carat is a unit of weight one carat equals 0.2 grams. Larger diamonds are rarer (in nature) and therefore more expensive, but carat weight alone doesn't determine value. A poorly cut 2-carat diamond will often look less impressive than a beautifully cut 1.5-carat stone.
For lab diamonds, carat weight is measured and recorded with the same precision as natural diamonds.
Which Grading Labs Certify Lab-Grown Diamonds?
Not all diamond certificates carry the same weight. Here are the labs you'll commonly encounter when shopping for certified lab-grown diamonds:
IGI — International Gemological Institute
IGI is the most widely used grading lab for lab-grown diamonds worldwide. They were early adopters of lab diamond grading, have dedicated lab-grown grading facilities, and issue detailed reports that are broadly accepted by jewellers and retailers. At Jacob Mercari, many of the lab-grown diamonds in our inventory carry IGI certification.
GIA — Gemological Institute of America
GIA is considered the gold standard in diamond grading globally. They began issuing lab-grown diamond reports in 2007 and updated their grading language in 2019 to use the full descriptive scale (rather than a simplified range). A GIA lab-grown diamond report carries significant credibility.
GCAL — Gem Certification and Assurance Lab
GCAL is known for its rigorous standards and offers a unique "0% Imperfect" guarantee — if a stone is graded Excellent in all cut parameters, GCAL backs it with a certificate guarantee. Their reports are detailed and trusted, particularly for round brilliant cut diamonds.
HRD Antwerp
HRD is a European grading authority with strong recognition in Belgium and the broader international market. They grade both natural and lab-grown diamonds using consistent standards.
Here's a quick comparison:
|
Grading Lab |
Lab-Grown Diamonds |
Natural Diamonds |
|
GIA |
Yes (since 2007) |
Yes |
|
IGI |
Yes — most widely used |
Yes |
|
GCAL |
Yes |
Yes |
|
HRD |
Yes |
Yes |
Our recommendation: Look for IGI or GIA certification when purchasing a lab-grown diamond. These two labs offer the most consistent, internationally recognized grading standards.
What Does a Lab Diamond Certificate Actually Show?
A grading report is a detailed document that typically includes:
• Report number — a unique ID you can verify on the lab's website
• Shape and cutting style — e.g., Round Brilliant, Oval Modified Brilliant
• Measurements — precise dimensions in millimetres
• Carat weight — to the nearest hundredth of a carat
• Colour grade — D through Z
• Clarity grade — FL through I3
• Cut grade — Excellent through Poor (for round brilliants)
• Polish and symmetry grades — indicators of craftsmanship
• Fluorescence — how the diamond reacts under UV light
• Clarity characteristics diagram — a plot of any inclusions or blemishes
• "Laboratory Grown" notation — clearly stated on all reputable reports
• Growth method — CVD or HPHT, as applicable
CVD vs. HPHT: Does the Growth Method Affect Quality?
Lab-grown diamonds are produced using one of two methods:
CVD (Chemical Vapour Deposition)
A carbon-rich gas is introduced into a chamber and broken down by microwave energy, causing carbon atoms to deposit onto a seed crystal layer by layer. CVD diamonds can achieve high colour grades and are increasingly common in the jewellery market.
HPHT (High Pressure High Temperature)
This method replicates the conditions under which natural diamonds form deep within the earth extreme pressure and heat applied to a carbon source alongside a metal catalyst. HPHT diamonds often have strong colour saturation and can exhibit a slightly different inclusion profile than CVD stones.
Neither method produces a universally "better" diamond. Quality depends on the specific stone, not the production method. Both CVD and HPHT diamonds are certified using identical grading criteria. The growth method will be noted on your certificate, which is simply informational disclosure not a quality judgment.
Red Flags to Watch For
Unfortunately, not all sellers are transparent. Here are some warning signs when evaluating a lab-grown diamond purchase:
• No certificate offered a legitimate loose diamond should always come with a grading report
• Unknown or unrecognized grading labs some sellers use in-house or obscure "labs" with no independent credibility
• Vague descriptions phrases like "near colourless" or "eye-clean" without documented grades are not substitutes for a certified report
• No way to verify the report always check the lab's database directly
• Pressure to buy quickly credible jewellers want you to review a certificate thoroughly before committing
Shopping for a Certified Lab Diamond in Canada
At Jacob Mercari, every loose lab-grown diamond we offer comes with a third-party grading certificate most commonly from IGI or GIA. We don't sell uncertified stones, and we encourage every client to review the grading report carefully before making a decision.
Our team walks you through the certificate, explains what each grade means for the stone's visual appearance, and helps you understand the trade-offs between the 4Cs within your budget. Because a 1.5ct VS1 G colour IGI-certified lab diamond means something very specific and you deserve to know exactly what you're getting.
Whether you're sourcing a loose diamond for a custom engagement ring or looking to compare a lab-grown and natural stone side by side, we're here to guide you through it.
Ready to explore certified lab-grown diamonds? Browse our diamond search tool or book a consultation with the Jacob Mercari team.
