About GUA


For over three decades, GUA has provided cutting-edge gemological research, testing, and laboratory analysis. This ongoing scientific work reflects the lab’s core commitment to protecting both the industry and its consumers. To that end, GUA delivers exemplary evaluations with clear disclosure of diamond, gemstone, and jewelry features, including known treatments.

But, science is only part of the GUA story. GUA also provides exceptional service:
an extensive variety of reports, a wide array of supporting services, and an open dialogue with customers and industry experts, that inspires the creation of exciting, new resources.

GUA ’s main office is located in the heart of New York’s diamond district, where it has provided this unique balance — of science and service — since 1977. The lab became independently owned and operated in 1986, and grew to include a west coast office in Los Angeles. Together, the labs evaluate diamonds and gemstones exclusively in North America, and continually set the standard as industry leaders.


  • Grading diamonds less than one carat in weight.
  • Using a photographic process to place identifying marks on diamonds.
  • Providing 72-hour service on diamond reports.
  • Issuing mini reports, containing complete full-size report data.
  • Introducing the SI3 grade to the diamond standard.
  • Utilizing x-ray digital imaging for pearl identification.
  • Detecting and announcing the presence of high pressure high temperature (HPHT)-treated colored diamonds (Type IIa) in the marketplace.
  • Creating a dedicated consumer hotline.
  • Offering state-of-the-art cold laser inscription.
  • Revealing that Type IaB HPHT-treated diamonds were made colorless and available
    in the marketplace.
  • Noting HPHT treatments on diamond reports.
  • Delivering full disclosure on lab-grown diamonds, via specialized reports and laser inscriptions on the stones.
  • Detecting and announcing the presence of chemical vapor deposition (CVD) lab-grown diamonds in the marketplace.
  • Developing a system to identify mounted lab-grown melee diamonds.
  • Identifying and establishing grading policies for a new generation of surface treated diamonds, with colored coatings.