GGTL Laboratories
The trade uses GGTL for diamond grading and testing and for gemstone identification including treatment and geographic origin assessment.
The record
What it covers
Reports it publishes
Named as the laboratory names them on its own site. Report contents and wording are set by the laboratory, not by us.
- Cullinan Diamond Report
- Cullinan Colourless Diamond Report
- Cullinan Coloured Diamond Report
Worth knowing
GGTL was formed in 2011 by the merger of GemTechLab in Geneva and Gemlab in Liechtenstein, both founded in 1996. It presents its Swiss and Liechtenstein laboratories as co-equal and designates no single headquarters, so no head office country or city is recorded here; addresses are given in Geneva, Eschen and Antwerp. No online report verification tool is offered.
Compiled from ggtl-lab.org, read on August 16, 2026.
We verify dealers, not stones. A laboratory report describes one stone on one date; it is not a guarantee of value, and it is not ours to stand behind.