Diamond certificates can be confusing. There are multiple laboratories, each with their own grading methodology, and the internet is full of conflicting advice about which certificate to trust. Here is what we know from years of working at the Israel Diamond Exchange, where certified diamonds change hands every day.
What a Diamond Certificate Actually Is
A diamond grading report (commonly called a “certificate”) is an independent assessment of a diamond’s characteristics. It documents:
- Carat weight — measured to the hundredth of a carat
- Cut grade — from Excellent to Poor (GIA) or Ideal to Poor (IGI)
- Color grade — from D (colorless) to Z (light yellow)
- Clarity grade — from FL (Flawless) to I3 (Included)
- Measurements — exact dimensions in millimeters
- Proportions — table %, depth %, crown angle, pavilion angle
- Fluorescence — None, Faint, Medium, Strong, Very Strong
- Inclusions map — a diagram showing the location of internal features
The certificate is not a valuation or appraisal. It is a factual assessment of the stone’s physical characteristics.
GIA: The Global Standard
The Gemological Institute of America is the most recognized and conservative grading laboratory in the world. GIA established the 4Cs grading system that the entire industry now uses.
GIA Strengths
- Most conservative grading — a GIA “G color” is truly a G color. There is no grade inflation.
- Universal recognition — every diamond dealer, insurer, and auction house in the world accepts GIA reports without question.
- Resale value — GIA-certified diamonds command the highest prices on the secondary market because buyers trust the grade.
- Consistency — GIA’s grading is highly consistent across its laboratories worldwide.
GIA Considerations
- GIA reports cost more to obtain, which can add to the diamond’s price
- GIA has historically focused on natural diamonds (though they now grade lab-grown as well)
IGI: The Lab-Grown Leader
The International Gemological Institute has become the dominant certifier for lab-grown diamonds and has a strong presence in the natural diamond market as well.
IGI Strengths
- Lab-grown expertise — IGI has certified more lab-grown diamonds than any other laboratory. Their grading methodology for lab-grown stones is well-established.
- Widely recognized — IGI is fully accepted by the trade and by major retailers worldwide.
- Competitive cost — IGI certification typically costs less than GIA, which can translate to lower prices for the consumer.
- Fast turnaround — IGI generally processes stones faster than GIA.
IGI Considerations
- Some industry professionals consider IGI grading to be slightly more generous than GIA (e.g., an IGI “G color” might be graded “H” by GIA). The difference, when it exists, is typically one grade.
- For natural diamonds intended as investment-grade purchases, GIA is generally preferred.
Which Should You Choose?
For Natural Diamonds
GIA is the safer choice. If you are spending significant money on a natural diamond and want the most universally trusted grade, go with GIA. The grade will hold up under scrutiny from any jeweler, appraiser, or insurer in the world.
For Lab-Grown Diamonds
IGI is the standard choice. IGI has the deepest expertise in lab-grown grading and the vast majority of lab-grown diamonds on the market carry IGI reports. There is nothing wrong with choosing a GIA-certified lab-grown diamond, but you will find a wider selection with IGI.
For Everyday Jewelry
For earrings, pendants, and pieces where the individual stone grade matters less than overall appearance, either laboratory is perfectly fine. You are buying for beauty, not for investment documentation.
What About Other Laboratories?
You may encounter certificates from other labs:
- IGL (International Gemological Laboratory) — reputable, used particularly in certain markets
- CGL — recognized in specific regions
- EGL — generally considered less consistent than GIA or IGI; exercise caution with EGL-certified stones
At Artisier, we use GIA and IGI exclusively for our primary certifications. These are the two laboratories we trust for consistent, accurate grading.
How to Read a Certificate
When reviewing a diamond certificate, focus on these elements in order of importance:
1. Cut grade — this has the greatest impact on how the diamond looks
2. Carat weight — confirms the actual size
3. Color and clarity — verify these match what you were told
4. Fluorescence — Strong or Very Strong fluorescence can sometimes affect appearance
5. Measurements — confirm these are consistent with the stated carat weight
The certificate number can be verified on the laboratory’s website (GIA: gia.edu, IGI: igi.org) to confirm it is genuine.
The Bottom Line
Both GIA and IGI are legitimate, respected laboratories. The difference between them is small and matters mainly to professionals and investors. For the vast majority of diamond buyers, either certificate provides the assurance you need: an independent, expert confirmation of what you are purchasing.
Every diamond at Artisier carries a GIA or IGI certificate. We work directly at the Israel Diamond Exchange, selecting and verifying each stone in person. View our certified collection →