A Jeweller’s Guide to Diamond Grading Reports: Are Lab-Grown Diamonds Graded Differently?
Diamond grading report with jeweller’s loupe examining a lab-grown diamond
As a jeweller in Hatton Garden, one of the most important conversations I have with couples revolves around the diamond itself.
You’ve likely heard of the 4Cs Cut, Colour, Clarity, and Carat but what you might not know is how these factors are officially graded, especially when it comes to lab-grown diamonds.
It’s a topic that’s seeing some big changes, and understanding them is key to making a confident and informed decision.
Over my 10 years in the UK jewellery industry, I’ve seen the rise of lab-grown diamonds transform the market, offering incredible value and quality.
But with this has come a wave of questions: Are they graded the same as natural diamonds? What do the reports from bodies like GIA and IGI actually mean? And what’s this I hear about GIA changing its entire system?
These are all fantastic questions.
A diamond grading report isn’t just a piece of paper; it’s the blueprint of your diamond, a guarantee of its quality, and a vital tool for ensuring you’re getting exactly what you paid for. Let’s demystify the world of diamond certification together, so you can feel empowered and excited about the beautiful stone you choose.
What Is Diamond Grading?
At its core, diamond grading is a standardised system used by gemological laboratories to assess a diamond’s quality.
This framework was developed to create a universal language that both jewellers and customers could use to understand and compare diamonds.
The most famous and widely accepted system is the 4Cs, established by the Gemological Institute of America (GIA) in the 1940s.
It provides an objective, scientific assessment of a diamond’s characteristics, which ultimately determines its value.
The 4Cs of Diamond Grading (Applies to Both Natural and Lab-Grown)
Whether a diamond is formed deep within the Earth over billions of years or created in a state-of-the-art laboratory, the same fundamental qualities are assessed.
Here’s a look at the 4Cs and how they apply to both types of diamonds.
Cut
Many people mistake ‘cut’ for a diamond’s shape (like round, oval, or pear).
In reality, a diamond’s cut grade refers to how well its facets interact with light.
It’s the only one of the 4Cs directly influenced by human hands.
A well-cut diamond will have exceptional brilliance (the reflection of white light), fire (the dispersion of light into the colours of the rainbow), and scintillation (the sparkle you see as the diamond moves).
This is arguably the most important ‘C’ because a poor cut can make even a high-quality diamond look dull. The grading scale is the same for both natural and lab-grown diamonds, ranging from Excellent to Poor.
Colour
When it comes to white diamonds, the colour grade actually refers to the absence of colour.
The GIA uses a D-to-Z scale, where D is completely colourless (the rarest and most valuable) and Z has a noticeable light yellow or brown tint.
This scale applies equally to both natural and lab-grown diamonds.
One of the advantages of the lab-growing process is that manufacturers have a high degree of control, which means lab-grown diamonds often achieve higher colour grades (like D, E, and F) more consistently and affordably than their natural counterparts.
Clarity
Clarity measures the presence of inclusions (internal characteristics) and blemishes (external characteristics). These are tiny imperfections that are often invisible to the naked eye.
The clarity scale ranges from Flawless (FL), where no inclusions or blemishes are visible under 10x magnification, to Included (I), where inclusions are obvious.
While both natural and lab-grown diamonds are graded on this same scale, the types of inclusions can differ due to their different formation processes.
For example, natural diamonds might have tiny crystals or feathers, while lab-grown diamonds might have small metallic remnants from the growth process.
A good London based jeweller will help you find an “eye-clean” diamond, where no inclusions are visible without magnification.
Carat Weight
This is the most straightforward of the 4Cs. Carat is a unit of weight, with one carat being equal to 0.2 grams.
It’s a consistent measurement, regardless of whether the diamond is natural or lab-grown. A 1.00-carat lab-grown diamond weighs exactly the same as a 1.00-carat natural diamond. Because lab-grown diamonds offer better value, you can often afford a larger carat weight for your budget without compromising on the other Cs.
Table showing the 4Cs explained for both natural and lab-grown diamonds
Where Diamond Grading Differs for Lab-Grown Diamonds
While the 4Cs provide a common framework, the key difference in grading lies in disclosure and origin.
Reputable grading labs will always clearly identify a diamond as being laboratory-grown on its report.
This is crucial for transparency and ensures you know exactly what you are buying. The language used is very specific, leaving no room for ambiguity.
Comparison table of key differences between natural and lab-grown diamond grading
How Diamond Certification Works: GIA vs. IGI
This is where things get really interesting, especially with recent changes in the industry.
The two most respected and widely recognised grading bodies for lab-grown diamonds are the Gemological Institute of America (GIA) and the International Gemological Institute (IGI).
GIA Diamond Grading: A Major Shift
The GIA is often considered the world’s foremost authority on diamond grading.
For years, they graded lab-grown diamonds using the same D-to-Z colour and internally Flawless-to-Included clarity scales as natural diamonds.
However, in a significant move, GIA announced a new system for lab-grown diamonds starting in late 2025. [1]
Instead of specific grades, GIA will now use broad descriptive terms:
• Premium: This category is reserved for the highest-quality lab-grown diamonds. To qualify, a stone must be D colour, VVS clarity or higher, with excellent polish and symmetry. [2]
• Standard: This category covers lab-grown diamonds that meet a combination of the “premium” criteria and a minimum threshold of J colour and VS clarity. [2]
Any lab-grown diamond that doesn’t meet the “Standard” criteria will not receive a quality assessment from GIA.
According to GIA, this change was made because over 95% of lab-grown diamonds fall into a very narrow, high-quality range, making the granular D-to-Z scale less relevant. [1] This new approach aims to simplify the assessment and further distinguish lab-grown diamonds from natural ones.
IGI Diamond Grading: The Trusted Standard
The IGI has been a pioneer in grading lab-grown diamonds since 2005 and is currently the most popular and trusted certification body for them. [3] Unlike GIA’s new approach, IGI continues to use the detailed 4Cs grading system for lab-grown diamonds. This means you will receive a specific colour grade (e.g., E) and clarity grade (e.g., VS1) on an IGI report.
Furthermore, an IGI report often includes more specific details, such as the growth method used (HPHT or CVD), which many find helpful.
This commitment to detailed, specific grading has made IGI the go-to standard for the lab-grown diamond industry, providing the transparency and assurance that consumers value.
Comparison table of GIA vs IGI diamond reports
Summary: Diamond Grading Criteria at a Glance
Navigating diamond reports can feel technical, but it boils down to this: you want a certificate from a reputable, independent lab that confirms the quality of your diamond. For lab-grown diamonds, IGI reports currently provide the most detailed and widely trusted assessments using the familiar 4Cs framework. While GIA’s new system is a significant development, the broader categories of “Premium” and “Standard” offer less specific information.
My advice is always to work with a jeweller who can walk you through the report, explain what it means, and, most importantly, show you the diamond itself.
A certificate is a guide, but your eyes, and the guidance of an expert, are your best tools.
Frequently Asked Questions (FAQ)
Are lab-grown diamonds graded using the same criteria as natural diamonds?
Yes, the fundamental quality criteria the 4Cs (Cut, Colour, Clarity, and Carat) are the same. However, major labs like GIA and IGI issue separate reports that clearly state the diamond is laboratory-grown, and GIA has recently moved to a different, broader grading terminology.
Why do lab-grown diamonds often have higher colour and clarity grades?
This is due to the controlled environment in which they are grown. Scientists can manage the process to minimise impurities and structural defects, making it easier and more common to produce diamonds in the colourless (D-F) and very slightly included (VS) ranges.
Is the cut grade different for lab-grown diamonds?
No, the cut grading scale and methodology are exactly the same.
A diamond’s cut is about its proportions and how it reflects light, and this is assessed identically for both lab-grown and natural diamonds.
Do lab-grown diamonds receive separate certification reports?
Yes, absolutely. Reputable gemological labs always issue distinct reports for lab-grown diamonds that explicitly state their origin to ensure full transparency.
Which certification bodies grade both natural and lab-grown diamonds?
Both GIA and IGI are leading authorities that grade both natural and lab-grown diamonds, though they now use different systems for their lab-grown assessments.
Can you visually tell the difference between a natural and a lab-grown diamond?
No. To the naked eye, a lab-grown diamond and a natural diamond of the same quality are visually identical. They have the same physical, chemical, and optical properties. Only specialised equipment in a gemological lab can definitively identify their origin.
About the Author:
Amr Ramadan is a certified gemologist (DGA) and the founder of Mouza Fine Jewellery, a Hatton Garden jeweller specialising in bespoke lab-grown diamond engagement rings. With over 10 years of experience in the UK jewellery industry, Amr is passionate about educating clients and helping them create their perfect, ethically sourced ring.
References:
[1] GIA. (2025, June 2). GIA to Use New Descriptive Terminology for Laboratory-Grown Diamonds. GIA News & Press. Retrieved from https://www.gia.edu/gia-news-press/new-descriptive-terminology-for-laboratory-grown-diamonds
[2] Graff, M. (2025, August 28). GIA’s New ‘Quality Assessment’ for Lab-Grown Diamonds Is Coming. National Jeweler. Retrieved from https://nationaljeweler.com/articles/14226-gia-s-new-quality-assessment-for-lab-grown-diamonds-is-coming
[3] IGI. (n.d.). Lab Grown Diamond Report & Certification For Authenticity. IGI. Retrieved from https://www.igi.org/reports/lab-grown-diamond-report/
