* Gemological lab
Central Gem Laboratory: reports, scope, and how to verify a certificate
Major Japanese gemological lab. Authoritative on Japanese-market jadeite (Type A grading) and pearls.
Published May 30, 2026
Quick facts
- Full name
- Central Gem Laboratory
- Headquarters
- Tokyo
- Country
- Japan
- Founded
- 1970
- Status
- Active
- Scope
- diamond, colored stone, pearl, jadeite
What they're known for
Major Japanese gemological lab. Authoritative on Japanese-market jadeite (Type A grading) and pearls.
Report types
- CGL Diamond Grading Report
- CGL Jadeite Identification Report
Each of these describes and grades a stone — its measured properties, quality, and any detected treatments. Note that a grading report is not an appraisal: most labs document what the stone is, not what it is worth in dollars.
How to verify a report
To confirm a CGL report is genuine, check the report number against CGL's official online verification and make sure every detail on the printed document matches the database record. If the stone carries a laser inscription on its girdle, confirm it reads the same report number under magnification. Be wary of photocopied, scanned, or altered certificates — always trust the lab's own lookup over a piece of paper.
* Frequently asked
FAQ
- Q. Is a CGL report an appraisal?
- A. No. A CGL report grades and identifies a stone — color, clarity, cut, weight, and any treatments — but it does not state a dollar value. For an insurance or resale figure you still need a separate appraisal that prices the stone against the current market.
- Q. What does CGL grade?
- A. Central Gem Laboratory covers diamond, colored stone, pearl, jadeite. Each report documents the stone's measured properties so two parties can describe the same item in the same language.
- Q. How do I check a CGL report is real?
- A. Enter the report number into CGL's official online verification at https://www.cgl.co.jp/ and confirm every detail matches the printed certificate. Check that any laser inscription on the diamond's girdle matches the report number, and be wary of photocopied or altered documents.
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