How GIA Grades Diamonds

Anonymity – to ensure objective and independent grading.

  • Every diamond is placed in a transparent storage case, and all owner references are concealed
  • Each stone is assigned a bar-coded label used to track it throughout the grading process
  • Client information is masked within the software used by GIA graders

Equality - to ensure all stones benefit from the same careful service each stone undergoes the same rigorous testing and grading procedures, regardless of size, origin or ownership.


Accuracy & Consistency – to ensure a rigorous and reliable scientific analysis

  • GIA is the leader in gemmological research and detecting the latest diamond and gemstone treatments and synthetics.
  • GIA laboratories maintain rigorous calibration standards for all lab instruments.
  • Every gemstone submitted is tested and screened at multiple steps during the grading process. If a determination is inconclusive at one lab location, the gemstone will be routed to another for further testing.
  • A global database captures hundreds of data points for every diamond during the grading process and is used by GIA researchers to detect emerging trends in treatments.
  • Control stones for diamond grading standards also move anonymously through GIA’s worldwide system to ensure uniformity of grading practices.
  • Teams of highly experienced quality controllers rotate through GIA laboratories worldwide training staff and ensuring adherence to consistent practices.

Integrity & Security – to safeguard the trust people everywhere have for GIA reports

  • An independent, third-party firm issues Global Compliance Reports to cover grader-to-client frequency and client servicing time, allowing GIA laboratories to spot potential breaches in conduct or security.
  • GIA’s database is a permanent repository of information on every diamond graded by GIA and a resource to track a lost or stolen diamonds.
  • All GIA employees are required to abide by a Code of Conduct to protect against conflicts of interest
  • GIA’s Ethics Policy and Code of Conduct are published on the Institute’s website. Any actual or suspected instance of potential misconduct can be reported anonymously from this link. All complaints are rigorously investigated.