Knowledge
17.04.2020 Gemstone Certificates & Grading Reports
How can you be certain that a gemstone is genuine? Even experts without a full set of laboratory equipment find it very difficult to check gemstones for authenticity and classify them correctly. It is even more difficult to determine whether a gemstone has been treated or enhanced, and it is nearly impossible to determine its origin without a laboratory.
Therefore, certificates and grading reports from independent gemological laboratories are important. These certificates specify the unique characteristics and qualities of a gemstone and verify its grading and authenticity.
Certification is of the utmost importance when buying gemstones because it reduces risk, increases the gem’s value, and is crucial for later resale.
Insurance companies also require a certificate in addition to a commercial invoice to insure a gemstone.

Gemstone certification
A gemstone certificate contains or proves the following:
- Gemstone name, e.g. “ruby” or “tanzanite”
- Type of mineral, e.g., for a ruby, it would be corundum
- A photo of the gemstone
- Weight in carats (ct.)
- Dimensions in millimeters
- Indicate whether it is a natural gemstone or a synthetic one
- Color, mostly including saturation
- Information on whether the gemstone is its natural color or has been treated (e.g., heat-treated)
- nformation on whether the gemstone has been treated in any other way (e.g., fracture-filled, impregnated, irradiated, or diffused)
- Optional: confirmation of the gemstone’s geographic origin
- For diamonds, include additional information on clarity, color grade, fluorescence, and the quality of the cut, symmetry, and polish
Be careful with “certificates” issued by gemstone dealers or jewelers! These are usually not recognized documents. In the case of resale, such “certificates” or “reports” are almost worthless.
For colored gemstones, certificates from Swiss labs such as the Swiss Foundation for Gemstone Research (SSEF), the Swiss Research Gemlab (GRS), or Dunaigre have the best international reputation. For diamonds, the best international reputation goes to diamond grading reports and dossiers from the GIA (Gemological Institute of America).
When buying gemstones, always look for certificates from independent gemological laboratories!

Which certificates are internationally recognized?



For colored gemstones, numerous institutes and laboratories issue recognized certificates and grading reports.
- Swiss Gemological Institute (SSEF)
- GemResearch Swisslab (GRS)
- Gübelin
- Dunaigre
- GIA
- Lotus
- International Gemological Institute (IGI)
- Gemmological Institute of India (GII)
- Ceylon Gem Lab (CGL)
- and others
For diamonds, certificates from the Gemological Institute of America (GIA) and the High Council for Diamonds (HRD) of the Antwerp Diamond Exchange are considered the two most important certifications.
Certificates from the International Gemological Institute (IGI) should also be mentioned.
Certificates for diamonds and colored gemstones are similar in structure.

Certifications for colored gemstones
Reports and certificates for colored gemstones differ in appearance depending on the issuing laboratory or institute.
In any case, a certificate must contain:
- Name of the issuing institute
- Certificate number
- A photo of the gemstone
- The stone’s dimensions, including its weight, to the nearest hundredth of a millimeter or hundredth of a carat (some institutes use the nearest thousandth of a carat.)
- The mineral, e.g., corundum or beryl
- The name of the gemstone , e.g., “ruby”
- A statement indicating whether it is a natural gemstone or a synthesis
- The color of the stone. For a ruby, “red” is derived from the gemstone itself. For a sapphire, the color needs to be specified.
- A statement about whether the stone is naturally colored, untreated or heat-treated.
- A statement as to whether the stone has been otherwise treated or enhanced (e.g., fracture-filled, impregnated, irradiated, or diffused)
- Optional: The geological origin of the gemstone.
Origin reports to confirm the geographic origin of a stone must be ordered separately by the owner.
For some stones, determining the origin makes no difference to the value: almost all intense yellow sapphires come from Sri Lanka.
It’s quite different with rubies, though. Since rubies from Burma fetch higher prices, determining the origin is essential.
The following special remarks about the color can be found in certificates for rubies:
- “Pigeon’s blood”: The most expensive color, it is only given to natural colored rubies and substantially increases the price.
- “Intense/vivid red”: this is a gradation to “pigeon blood” and also increases the price.
For blue sapphires, there are two internationally sought-after color grades:
- “Royal blue”: This designation, given to a dark blue with high saturation and brilliance, is the most sought after and valuable.
- “Cornflower blue”: This color grade is also highly valuable. It describes a very pure blue.
The cost of a certificate ranges from around 30 euros at a local institute in countries like India or Sri Lanka to several thousand euros for high-quality, rare gemstones. Thus, the purchase price of the gemstone also influences the type of certificate received when buying a stone. For example, if the stone costs 500 euros, the buyer cannot expect an SSEF or GRS certificate.
The determination of origin can be ordered extra by the owner of the stone. It is usually expensive and often adds up to 50% of the total cost of the certificate.

Diamond grading reports: GIA or HRD


The two primary laboratories that certify diamonds are the Gemological Institute of America (GIA) and the HRD. Certificates from other labs may lead to significant price reductions when reselling.
In the past, certified diamonds were sealed in plastic boxes. The certification number was on the plastic box, linking the diamond to the certificate. Today, this method is outdated. Now, the certificate number is laser-inscribed on the girdle of the diamond (the thin outer edge) in letters no larger than a few micrometers, making it invisible to the naked eye. This establishes the connection between the diamond and the certificate.
To check if the certificate is genuine, enter the certificate number on the certifying institute’s website to receive a scan of the certificate. (Of course, ownership data is not public.)
A diamond certificate is considered part of the proof of ownership. In any case, certificates should be kept separate from gemstones.
Here is a note about the types of GIA diamond certificates: If the diamond weighs more than one carat, the “GIA Diamond Grading Report” (8.5 x 3.7 inches) is enclosed. If the diamond weighs less than one carat, the “GIA Diamond Dossier” measures 12.8 by 9.3 centimeters.
The contents are indicated in the diamond certificate:
- Certificate number
- Cut (brilliant, emerald, oval or princess cut, etc.)
- Diamond dimension to the nearest hundredth of a millimeter
- Weight in carats to the nearest hundredth of a carat
- Color grade from D to Z
- Clarity grade from FL to P3
- Cut grade from “excellent” to “poor”
- Polish from “excellent” to “poor”
- Symmetry from “excellent” to “poor”
- Fluorescence ranges from “none” to “strong”
- Other characteristics of the diamond
- A profile of the cut
- For diamonds heavier than one carat, a schematic representation of the inclusions is also provided, if applicable.
Most certificates omit a photo of a white diamond because it would not provide much information; the above parameters are more important.
Usually, all white diamonds of good quality weighing 0.33 carats or more are certified. If the weight is less than that and the buyer wants a certificate, they will be charged separately for it.
For colored “fancy diamonds,” the color is not mentioned on the D-Z scale, but rather, the corresponding color designations are used (e.g., “fancy intense yellow”). All other information remains the same. GIA certificates for colored diamonds (GIA Colored Diamond Identification and Origin Report) are always 21.6 x 9.3 cm.