Field report · 897
Reading a stone's certificate: GIA, GIT, GRS
The three lab certificates you'll see in commerce, what they actually tell you, and which ones to trust.
For stones above $500, you'll often see a lab certificate. The certificate isn't a guarantee of value — it's a statement of fact about the stone's identity, origin, and treatments. Here's how to read them.
The three labs you'll see most
GIA (Gemological Institute of America)
Headquartered in Carlsbad, California. The most-respected lab in the diamond trade and very strong on colored stones. GIA certificates are conservative — they identify the stone, treatments, origin (sometimes), and key parameters (weight, dimensions, color grade for diamonds, etc.).
For colored stones, GIA's reports include:
- Identity (e.g., "natural ruby")
- Origin (when determinable)
- Treatment indication (heat, oil, none, etc.)
- Dimensions and weight
- Color description (no formal grading scale for color in colored stones)
GRS (GemResearch Swisslab)
Headquartered in Lucerne, Switzerland. Specialty: high-end colored stones, especially ruby, sapphire, emerald. Known for detailed origin determination and color grading. GRS uses descriptive color codes like "vivid red" or "royal blue" — these are GRS-specific marketing terms with real meaning at high end, but be aware they're trade language.
GIT (Gem and Jewelry Institute of Thailand)
Bangkok-based. Standard for Burmese and Sri Lankan stones often runs through GIT. Quality is generally good but reports are sometimes considered less rigorous than GIA or GRS for serious investment purchases.
What's NOT on a certificate
Important: a lab certificate does NOT tell you:
- The price — labs don't appraise market value
- Whether you're getting a fair deal
- The stone's history (provenance from mine to seller)
- Future treatment risks (oiled stones can deteriorate)
Other labs you might encounter
- AGL (American Gemological Laboratories) — US-based, well-regarded for colored stones
- SSEF (Swiss Gemmological Institute) — premium European lab
- Gübelin — Swiss, considered the gold standard for top-tier colored stones
- EGL (European Gemological Laboratory) — historically inconsistent quality; treat reports with skepticism unless from a specific EGL location with a strong reputation
When you should get a certificate
- Any colored stone above $1,000 — verify identity and treatment
- Any stone described with origin claims (e.g., "Kashmir sapphire")
- Any natural-claim that might be synthetic or treated
For everyday cabochons, faceted stones in the $50-300 range, and specimens for display, certificates are usually overkill. The cost ($50-500 per stone) doesn't pay back unless you're insuring or reselling.