Can I trust an SGL diamond certificate?

Question

Accepted Answer

Yes, with limits. The Singapore Gemmological Laboratory (SGL), founded in 1999, issues independent grading reports against an internally consistent framework. SGL is recognised in the Asian trade and used by several South African dealers on smaller stones (below 0.50 carats) where the GIA fee is disproportionate. On stones above 0.50 carats, the trade convention is to insist on a GIA report. SGL is a legitimate, independent, third-party laboratory. Its grading framework is internally consistent and has been audited by international trade observers. For stones below 0.50 carats, accent stones in a setting, smaller pendants, ear-stud pairs, an SGL report is acceptable in the South African trade. The fee structure is more proportionate to the stone’s value than the GIA fee on the same small stone. What SGL does not have is GIA’s weight in the international resale, insurance, and high-end retail context. A GIA-graded stone trades and resells at a premium relative to the same stone graded by SGL. For any stone above half a carat that you might one day resell, insure on a fluctuating market, or move internationally, GIA is the document the trade expects. EGL is a different question. EGL grades commonly run one to two steps softer than the GIA equivalent, which materially affects pricing. The full lab landscape is set out in A reader’s guide to South African diamond certificates. Lab-comparison detail is also documented in SA diamond statistics 2026.