One of the largest organizations of diamond and colored gemstone grading and identification, with many franchises all over the world. The EGL-USA is a little more conservative and consistent than the rest in my opinion.
Here is a description from the EGL-USA website:
“For over three decades, EGL USA 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, EGL USA delivers exemplary evaluations with clear disclosure of diamond, gemstone, and jewelry features, including known treatments.
But, science is only part of the EGL USA story. EGL USA 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.
EGL USA’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 certify diamonds and gemstones exclusively in North America, and continually set the standard as industry leaders.”