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Accredited Gem Laboratory

Professional Gemological Identification Services

The Accredited Gem Lab® (AGL) designation means the firm you are shopping with has the minimum equipment required to perform gemological testing and appraisals. The equipment includes a gemological darkfield binocular microscope (essential for gemological observations), a master color grading set per American Gem Society (AGS) Standards (for reliable color comparisons of diamonds), a gemological library of reference materials, and more.

Firms with the Accredited Gem Lab® designation prove to their customers and clients they are vested in the thorough inspection of gemstones and jewelry. More importantly, each Accredited Gem Lab® is required to have an AGS titleholder on staff, with a minimum of a Certified Gemologist® (CG) or Certified Gemologist® Appraiser (CGA) title to oversee its use. This ensures that a fully-credentialed gemologist with the proper knowledge is responsible for gemological testing and appraising.

If you are in the jewelry industry and would like to learn more about how to qualify for an AGL designation, please click on the sections below or contact

The American Gem Society (AGS) Gemological Sciences Committee is dedicated to keeping the Accredited Gem Lab® (AGL) designation relevant, which helps support the AGS mission of consumer protection, ongoing education, and a high standard of business ethics. As a result, the requirements to qualify as an AGS Accredited Gem Lab® are currently being reviewed and updated. Please note that these requirements must be met by a Retail or ICGA firm member holding, or applying for the AGL designation:

  1. The firm must have a Certified Gemologist (CG)® or Certified Gemologist® Appraiser (CGA or ICGA) in its employ to directly supervise the gem laboratory;
  2. The firm must have the laboratory located within the premises of the firm member and have physical facilities permitting the proper use and display of the gem testing equipment;
  3. The firm must have and maintain an adequate and current gemological library which may be virtual or online and must include an edition of The Practical Guide to Jewelry Appraising by Cos Altobelli, ECGA; and
  4. The firm must have the laboratory equipped with the following testing instruments, tools and reference material, as a minimum:
    1. AGS Color Master Diamond Comparator Set, consisting of at least five AGS Master Diamonds which have been graded by the AGS Laboratories for color according to the AGS color scale. The girdles must be polished or faceted and laser inscribed to identify them as Master Diamonds. (See Color Master Requirements below)
    2. Color comparison set for colored gemstones and fancy colored diamonds such as Gem Dialogue, Munsell, GIA, GemeWizard, AGL ColorCodex or similar
    3. Darkfield binocular microscope (minimum 10x with overhead fluorescent light attachment)
    4. Diamond scales to 1/100 carat, scale attachments/hydrostat for determining specific gravity recommended
    5. Dichroscope
    6. Internet connection
    7. Lighting source: Daylight equivalent (approximately 6500 degrees Kelvin)
    8. Measuring device (Leveridge gauge or millimeter gauge)
    9. Metals tester
    10. Photography equipment (cell phone or digital camera acceptable)
    11. Polariscope
    12. Refractometer with polarizing plate and RI fluid
    13. Laboratory-grown diamond screening and detection equipment with minimum standards (See Approved Diamond Screening Equipment below)
    14. Ultra-violet light, both longwave and shortwave

It is also recommended, but not required that the firm have:

    1. Diamond probe (thermal and electrical conductivity meters to screen for diamond simulants)
    2. Fiber Optic Light Source
    3. Non-Contact Optical Scanner
    4. Spectroscope

An Accredited Gem Lab® is subject to audit without notice for compliance for the above elements. If the audit identifies noncompliant elements, the titleholder that oversees the AGL (AGL Contact) will have two years from the date of notice of noncompliance to bring the AGL back to good standing.

The following outlines the requirements for the AGS Color Master Diamond Comparator Set for the Accredited Gem Lab® (AGL) designation. 


Color: The first diamond must be 0.0 (D), 0.5 (E) or 1.0 (F). Each additional diamond can be no greater than one (1) numerical AGS color grade variation from the previous diamond. For example, if the first color master diamond is an AGS 0.5 (E), the next diamond must be an AGS 1.0 (F) or AGS 1.5 (G). Single or split grades may be assigned according to the Colorimeter Conversion Table under “Grading Results”.

AGS Color Scale

Fluorescence: Master diamonds must not have visible fluorescence. Since fluorescent diamonds can vary in color grades between daylight and artificial light, they are not appropriate color masters. In colors lower than AGS 3.5 (K), faint fluorescence may be accepted. 

Cut: Diamonds should conform to the same general proportions. The difference in the appearance of the color of a shallow diamond and a deep diamond, due to the additional depth of the latter, make accurate comparisons more difficult. All diamonds in the set should be of approximately the same size and proportions. 

Clarity: Slightly included diamonds are acceptable, providing that the characteristics do not affect the color or transparency of the diamond. 

Weight: Diamonds must weigh 0.30 carats or more and must be unmounted. This size is adequate for comparison of diamonds up to 1.00 carat. 

Girdle: Diamonds must have polished or faceted girdles and there should not be large girdle thickness variations from one stone to another. 

Laser Inscription: Each Color Master Diamond will be laser inscribed with the AGS number, estimated Colorimeter value, and the equivalent master color grade.

The following equipment from the ASSURE Directory of Diamond Verification Instruments will qualify for the Accredited Gem Lab® designation: 

Instruments under $10,000

Instruments over $10,000

GIA iD100 

DiamondDect 3 

Sherlock Holmes Device

AMS2 (melee only)



GIA DiamondCheck

M-Screen+ (melee only)


Do you meet the requirements to become an Accredited Gem Lab® (AGL)? If so, apply today by completing this application and submitting to

Questions? Contact membership at or 866.805.6500, option 3.