Diamond Certificates Explained: IGI, GIA and GCAL, and Whether You Need One
A diamond certificate is the only way to know exactly what you are paying for. What IGI, GIA and GCAL reports contain, how to check one, and when you can do without.
A diamond certificate, more accurately called a grading report, is an independent laboratory's description of one specific stone. It is the only reliable way to know what you are paying for, because two diamonds that look identical in a shop can differ a great deal in cut, colour, clarity and origin. Here is what Canadian buyers should know.
Quick answers
- Do you need one? For any centre stone of about 0.30 carat or more, yes.
- IGI or GIA? Both are respected independent labs. IGI grades most lab-grown diamonds sold worldwide; GIA is best known for natural stones.
- Always verify the report number on the lab's website before you pay.
What a diamond certificate is (and is not)
A grading report records the measurable facts about a diamond: its carat weight, dimensions, colour and clarity grades, cut quality, polish, symmetry, fluorescence and, crucially, whether it is natural or laboratory-grown. It is not a valuation or an appraisal: it does not tell you what the diamond is worth or what to insure it for. For that, you need a separate valuation.
The main laboratories
| Lab | Known for | Lab-grown reports |
|---|---|---|
| IGI (International Gemological Institute) | The largest grader of lab-grown diamonds; labs in Antwerp, New York, Mumbai, Surat and elsewhere | Full 4Cs grading with origin clearly stated |
| GIA (Gemological Institute of America) | Created the 4Cs and the modern colour and clarity scales; the reference lab for natural diamonds | Grades lab-grown diamonds and states the origin |
| GCAL (Gem Certification & Assurance Lab) | New York lab known for detailed cut analysis and optical performance images | Grades natural and lab-grown diamonds |
Grading standards are similar but not identical between labs, so compare like with like: two "G VS1" diamonds graded by different labs may not look exactly the same.
How to verify a certificate in two minutes
- Find the report number on the certificate or the seller's listing.
- Look it up on the lab's official website (IGI and GIA both offer free online report checks).
- Compare every detail: weight, measurements and grades must match the diamond you are buying.
- Check the inscription. Most graded diamonds carry the report number laser-inscribed on the girdle; any jeweller can show it to you under magnification.
When is a certificate essential?
Insist on a report for
- Engagement ring centre stones
- Solitaire studs and pendants over about 0.30 ct
- Any loose diamond
- Anything sold as natural
Usually fine without
- Small accent stones in a halo or pavé band
- Melee diamonds in tennis bracelets (ask for the total carat weight and quality range instead)
Buying in Canada from overseas
When you buy online from another country, the report becomes even more important, because you cannot see the stone before it ships. Ask for the report number before you order, and make sure the original report comes with the jewellery. At Zarna Jewels our diamonds are graded by independent labs, mainly IGI, with GIA and GCAL reports available, and every order is fully insured and tracked until it is signed for, with the delivery charge shown at checkout. Our prices do not include Canadian import charges; any duties or taxes due on arrival are collected by the courier.
Certified centre stones
Is IGI as good as GIA?
Both are respected independent labs. GIA is the long-standing reference for natural diamonds; IGI grades the majority of lab-grown diamonds sold worldwide. What matters most is that the report is from an independent lab and can be verified.
Does a certificate prove a diamond is natural?
A report from a major lab states the origin. A natural diamond's report says natural; a lab-grown diamond's report says laboratory-grown.
Is a certificate the same as an appraisal?
No. A certificate describes quality; an appraisal or valuation estimates a value, usually for insurance.
