Understanding Diamond Certificates: GIA, IGI, HRD Explained
A diamond certificate is your assurance of quality and authenticity. Learn what these documents mean, which labs to trust, and what to look for when buying in Thailand.
A diamond certificate (also called a grading report) is an independent assessment of a diamond's characteristics by a gemological laboratory. It's like a passport for your diamond—verifying its identity and quality.
Why Certificates Matter
Without a certificate, you're trusting the seller's word about quality. A certificate provides:
- Objective grading: Independent labs have no financial interest in the sale
- Comparison basis: Compare diamonds accurately using standardized grades
- Insurance documentation: Required for insuring valuable jewelry
- Resale value: Certified diamonds command better prices
- Fraud protection: Confirms the diamond is natural or lab-grown as stated
The Major Grading Labs
GIA (Gemological Institute of America)
GIA is the gold standard in diamond grading. They created the 4Cs system and are known for the most consistent, strict grading standards in the industry.
- Best for: Natural diamonds, highest confidence in grades
- Reputation: Most respected worldwide
- Strictness: Most conservative grading (a GIA G color may be an F elsewhere)
- Cost: Premium pricing for certification
IGI (International Gemological Institute)
IGI has become the leading lab for lab-grown diamond certification and is widely respected for natural diamonds as well.
- Best for: Lab-grown diamonds, good for natural diamonds
- Reputation: Highly respected, especially in Asia
- Strictness: Slightly more lenient than GIA (1-2 grade variance possible)
- Cost: More affordable than GIA
HRD (Hoge Raad voor Diamant)
Based in Antwerp, Belgium—the historic center of diamond trading—HRD is respected in European markets.
- Best for: European market diamonds
- Reputation: Strong in Europe, less common in Thailand
- Strictness: Generally comparable to IGI
- Cost: Mid-range pricing
What's on a Diamond Certificate?
A typical certificate includes:
- Unique report number: Verifiable on the lab's website
- Shape and cut: Round brilliant, princess, oval, etc.
- Measurements: Exact dimensions in millimeters
- Carat weight: Precise weight to the hundredth of a carat
- Color grade: D (colorless) to Z (light color)
- Clarity grade: FL (flawless) to I3 (included)
- Cut grade: Excellent to Poor (for round brilliants)
- Polish and symmetry: Surface quality assessments
- Fluorescence: None to Strong Blue
- Inclusion plot: Diagram showing location of inclusions
How to Verify a Certificate
Always verify certificates online:
- GIA: gia.edu/report-check
- IGI: igi.org/verify
- HRD: my.hrdantwerp.com
Enter the report number and compare the details with the physical certificate. If anything doesn't match, walk away.
Thailand-Specific Advice
- Always insist on certification: Reputable Thai jewelers will have no problem providing certificates
- GIA and IGI are most common: These are widely recognized and easily verified in Thailand
- Be wary of "in-house" certificates: Store-issued certificates aren't independent—insist on third-party lab reports
- Laser inscription: Many certified diamonds have the report number laser-inscribed on the girdle for verification
Our Recommendation
For natural diamonds, prioritize GIA certificates for the highest confidence in grading accuracy. For lab-grown diamonds, IGI is the industry standard and equally trustworthy. Avoid uncertified diamonds or those with certificates from unknown labs.
Shop Certified Diamonds
Every diamond at GlitzJewelry.com comes with GIA or IGI certification. View certificates online before you buy.
Browse Certified Diamonds at GlitzJewelry.com