Think of a grading report as your diamond's independent identity document. It is a record of exactly what your stone is, produced by a laboratory that has no stake in selling it to you. When a purchase carries this much weight, that independence is the whole point.
Here is what a report actually covers, which laboratory names to trust, how to check the document is genuine, and the one thing it cannot tell you, along with a change that is about to shift that last part.
What a grading report actually tells you
A report describes your diamond against the 4Cs, which are cut, colour, clarity and carat weight. It records the exact measurements and proportions, and it maps the stone's individual characteristics, the tiny internal features that make your diamond identifiably itself rather than any other.
That last detail matters more than it sounds. Those characteristics act like a fingerprint, and most reports are paired with a laser inscription on the diamond's girdle, a microscopic report number invisible to the eye but readable under magnification. Together they link your stone and its document permanently. Years from now, any jeweller can read the inscription and match it to the report, which means no substitution and no doubt about which diamond you own.
Which laboratory graded it matters
Not all reports carry the same authority, and the name on the document tells you a great deal.
GIA, the Gemological Institute of America, created the 4Cs and remains the benchmark for natural diamonds, valued for consistency and independence. IGI, the International Gemological Institute, has become the standard for lab-grown diamonds and is trusted by most major retailers for them.
There is a recent change worth understanding, because it affects what you will see. As of 1 October 2025, GIA stopped applying the 4Cs to lab-grown diamonds. Rather than a detailed colour and clarity grade, a lab-grown stone assessed by GIA is now described simply as Premium or Standard, or given no assessment if it falls below the threshold. IGI, by contrast, still issues a full detailed 4Cs report for lab-grown stones, including the growth method. The practical result is straightforward. If you are looking at a lab-grown diamond, an IGI report is entirely normal and reputable, and often more informative than the simplified GIA assessment. For a natural diamond, GIA remains the name to look for.
Reading across labs, and a fair word on grading
One honest point that saves confusion. When the same stone is graded by different labs, the results can differ slightly. In practice IGI tends to grade a little more leniently than GIA, often by around a single grade in colour or clarity. This is not a reason to distrust either. It simply means you should compare a stone to others graded by the same lab, rather than assuming an IGI colour grade and a GIA colour grade mean precisely the same thing.
The sensible approach with a lab-grown IGI report is to set yourself a quality floor rather than chase the top of the scale, since most lab-grown stones sit in a narrow, high range anyway. We are happy to talk you through where that floor should sit for the stone you are considering.
How to check a report is genuine
A report is only worth what you can verify, and this takes a moment. Every GIA and IGI report carries a unique number, and both laboratories have a free report-check tool on their own website. Enter the number and the details should match the document in front of you exactly.
A few things should make you pause. An in-house certificate written by the retailer rather than an independent lab. A photocopy rather than a report you can verify online. A missing report number, or one that returns no match. None of these means a stone is bad, but each is a reason to ask more questions before you commit.
Why a report protects you
Beyond confirming quality, a report does real practical work.
Insurance is the clearest example. Insurers want an independent description of the stone to value and cover it correctly, and a report gives them exactly that, along with the fingerprint needed to identify your diamond if it is ever lost or stolen and later recovered. It matters for future valuation and resale too, since a valuer can see what they are dealing with rather than taking anyone's word for it. And on a quieter level, it is simply peace of mind. You know what you have, in writing, from a source with nothing to gain.
What a report will not tell you, and what is about to change
Here is the part most guides skip. A grading report tells you what a diamond is. It does not tell you how beautiful it looks. Two stones with near-identical reports can perform very differently in the light, one bright and full of life, the other flat.
This is sharpest on fancy shapes. At present, only round brilliant diamonds receive a full cut grade. Oval, pear, marquise and the rest are assessed for polish and symmetry but not given an overall cut grade, so the paperwork cannot currently tell you whether a fancy-shape stone was cut well, which is exactly where cut varies most and where the bowtie shadow lives.
That is starting to change. GIA has announced it will begin giving cut grades to selected fancy shapes from 2027, starting with oval, pear and marquise. It is a welcome move, and a clear sign of how much cut on these shapes has always mattered. Until it arrives, and for every other shape, your own eyes remain the test. Look at the stone in daylight, move your hand, and watch whether it stays alive. The report confirms the facts. Your eyes tell you how the diamond will actually look on the hand.
Every diamond we set comes with its grading report, and we will talk you through exactly what yours means rather than handing you a document and leaving you to decode it. If you would like to see a graded stone in person, you are welcome at 35 Frederick Street in Birmingham's Jewellery Quarter. You can book a consultation here.