Laboratory
Central Gem Laboratory (CGL)
Tokyo, Japan
Diamonds, coloured stones, pearls
Central Gem Laboratory (CGL), founded in Tokyo in 1970, is one of Japan's largest gem laboratories, serving the Japanese jewellery trade.
What it does
Diamond grading, coloured stone and pearl identification, and research. CGL reports are widely used in Japanese retail.
Using any laboratory
- Ask what the report will state (identity, treatment, origin, grade) and how long it takes; turnaround and fees change.
- Check a report online with the laboratory's own report-check service, and match the stone to the report.
- Reports from different laboratories can differ, especially on colour grades, treatment and origin. A report is an opinion based on the tests made, not a valuation.
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