GIA, IGI, Gübelin and SSEF — which cert lab to trust

The big four (and why)

• GIA — the global benchmark for diamonds and increasingly for coloured stones. Conservative origin calls. Slow turnaround in some markets.
• SSEF (Switzerland) — the gold standard for high-value coloured stones, especially rubies, sapphires and Colombian emeralds. Origin determinations are taken as the final word in the trade.
• Gübelin (Switzerland) — peer to SSEF, with the additional Gemstone Rating service which judges overall quality on a single scale.
• AGL (New York) — leading US lab for coloured stones. Useful when SSEF or Gübelin turnaround is unworkable.

Useful regional labs

• GRS (Bangkok / HK) — common in the Thai trade; widely accepted but interpret colour grades carefully.
• Lotus Gemology (Bangkok) — boutique lab respected for fine ruby and sapphire work.
• GIT (Bangkok) — state-run, useful for export documentation.
• IGI — fast and economical for diamonds and commercial coloured stones.

When to insist on a cert

Any single stone above roughly USD 3,000 should travel with a recent independent report. Calibrated commercial goods normally do not — but the dealer should still be able to state treatment in writing on the invoice.