Certification Explained: GIA, GRS, SSEF, Gübelin and the Rest

What a certificate actually buys

A gemological report is an independent confirmation of four things: species (is this actually a sapphire?), origin (where it was mined), treatment (has it been heated, oiled, diffused, or irradiated?), and quality factors (weight, measurements, color grade where applicable). For stones above roughly 1 carat, the cost of a report — $50 to $500 depending on lab and stone — is a tiny fraction of price and a very large fraction of resale confidence.

Below 1 carat, certification often costs as much as the stone itself and is usually skipped.

GIA — the universal standard

Gemological Institute of America. Founded 1931, U.S.-based with branches worldwide. The reference lab for diamonds. For colored stones GIA is competent but conservative — its origin calls are more cautious than the Swiss labs below, so collectors looking for a "Kashmir" or "Mogok" determination often go elsewhere.