A certificate is only as useful as the laboratory that issued it. For jade, this matters more than for most gemstones, because treatment terminology differs between the Chinese market and international laboratories. This guide explains what to ask for and how to read the answer.
Which laboratories and standards matter
In China, the most recognised testing body for jade is NGTC (National Gemstone Testing Center), which issues reports widely used by buyers and sellers. Internationally, laboratories such as GIA provide education and grading services for jadeite and nephrite, and other major gemological laboratories also test jade. For naming and classification of jade in China, the relevant national standards are GB/T 16552 (classification and nomenclature of gems) and GB/T 16553 (testing and identification). A report should identify the material and state the testing method in a way you can check.
No laboratory certifies beauty or market value. What a good report can state is that the material is jadeite or nephrite, whether it is natural in colour, and whether treatment such as bleaching, polymer impregnation or dyeing is present.
What to check on the report
- The name and full contact details of the laboratory.
- The exact report number and the photograph of the stone.
- The material identification and any statement about colour or treatment.
- The date and the method used (for example infrared or magnified inspection).
- Whether the weight and measurements match the piece you are buying.
Should the certificate repeat the word A-grade?
Some Chinese reports do, but the phrase that matters is the finding about colour and treatment. A report that records natural colour and no detected polymer or dye answers the real question behind the A-grade label.
How do I verify that a certificate is genuine?
Contact the laboratory directly with the report number, or use its online verification service if one exists. Do not judge a report by its cover design - check it with the issuer before payment, especially for high-value pieces.
What to ask the seller alongside the certificate
- Daylight and backlight photographs of the exact stone.
- What the seller will do if the report does not match the piece.
- Whether the report covers this stone or a similar one.
You can request photographs and discuss documentation on any piece in our jadeite or Hetian collections before you order.
Sources: GIA education pages on jadeite and nephrite; NGTC at ngtc.org.cn; China national standards GB/T 16552 and GB/T 16553. Always verify a report with the issuing laboratory.