A diamond’s certificate represents a third-party’s evaluation of the diamond’s condition on a specific date.
It should tell you:
- The inspection date
- Shape
- Cut style
- Diamond measurements (length, width, and height)
- Carat weight
- Color grade
- Clarity grade
- Additional information the diamond graders found
It might also include:
- Cut grade
- Fluorescence
- Finish’s polish
- Finish’s symmetry
- Comments from the grader
- Laser inscription
- Notes on enhancement treatments performed on the diamond
- A map of inclusions and/or blemishes
- Clarity characteristics
- Diagram of diamond’s actual proportions
- Photo or diagram of diamond’s “hearts and arrows” pattern
If you plan on paying a third-party to certify your diamond, ask to see a sample certification first. Make certain the proposed certification will cover all of the areas you expect to be included.
Does my diamond really need a certificate?
No, your diamond does not need to have a certificate.
Diamonds without certificates should cost less than their certified counterparts. For example, one popular jewelry retailer sells a round, one-carat solitaire diamond in a 14-karate white gold ring for $3,100. The same jeweler sells a ring with the same description, plus the word “certified” for $4,800. Both diamonds are H-color, one-carat, round. One’s clarity is I1; the other’s clarity is SI2-I1. So, they may be exactly the same diamonds, except one is certified.
However, some people prefer to have a certificate, for various reasons:
- They want a reputable, independent third-party to verify the color, cut, clarity, and carat weight of the diamond.
- They feel a certificate provides assurance this is not a “blood diamond” or “conflict diamond.”
- They want certification for insurance purposes.
- They want the diamond to have a laser-inscribed number and certificate in case of theft, so police will identify their diamond if it turns up during an investigation.
- They want certification for ease in reselling—or returning—the diamond.
- Someone they know bought a pretty piece of glass, moissanite, or cubic zirconia, thinking it was a diamond.
- They think a relative or friend might imply the diamond is not what it appears to be, and they’d rather have proof available.
But not everyone has these concerns. When shopping for a diamond, each individual must balance his own personal thoughts against the prospect of saving money. In the end, the decision of whether or not to seek a diamond with a certificate—or even a particular certification laboratory—is up to the individual buyer.
How do gemological laboratories test diamonds for certification?
While each gemological laboratory has its own standards and procedures, this answer focuses on the Gemological Institute of America (GIA). The GIA is one of the best-known gemological laboratories, and GIA makes no secret of its diamond testing and certification procedures.
When the GIA receives a loose diamond, it separates the diamond from anything that might reference the diamond’s owner—logos, letterheads, packing materials, etc. All diamonds are placed in individual transparent storage cases, each with a GIA identifier. In this way, the GIA assures the diamond graders make no subliminal connection between an individual diamond and its owner.
Each diamond is electronically tracked as it makes its way through the GIA diamond certification process. Diamonds that do not already have an inscribed GIA report number can have one microscopically inscribed on the diamond girdle at the client’s request.
After each grader’s inspection, the individual diamond is returned to GIA’s Inventory Control Department. This group coordinates the distribution of diamonds for evaluation, making certain the diamond progressively visits four different diamond graders, each grader more senior than the previous. The GIA Inventory Control Department also routes the diamonds so that exactly who evaluates which diamond is somewhat random, selecting from the hundreds of diamond graders working in each GIA laboratory.
After all four diamond graders have entered their assessments into the GIA software, a report is generated and matched with the corresponding diamond. At that point, client anonymity is no longer an issue. The evaluated diamond and its report are prepared for return to the client.
Measuring Carat Weight
The diamond’s first stop is the GIA Weights and Measures Department. A highly accurate electronic micro-balance weighs diamonds to the fifth decimal place. All of a diamond’s measurements, proportions, and facet angles are captured with an optical measuring device. All of the information is entered into the GIA’s operations and information management system, Horizon.
The weight and measurements are added to the label used for the diamond’s transparent storage case. Each case is labeled with a GIA internal identification number, as well as the specific services requested for that particular diamond.
The diamond is next sent for testing to determine whether the diamond is real or a synthetic substitute. The tests also look for the possibility of diamond enhancements, which mask a diamond’s original condition. The GIA uses Fourier transform infrared spectrometry (FTIR) and Raman spectroscopy to determine a stone’s identity and color origin. This equipment also evaluates colored diamonds.
Grading Diamond Clarity
The first diamond grader identifies finish and clarity characteristics under 10x magnification. This examination includes looking for filled fractures and laser drilling, as well as tests designed to alert the grader to whether a stone has been cosmetically treated or is possibly not a real diamond.
The GIA has a database of hundreds of diamond diagrams. The first diamond grader selects the diagram closest to the diamond’s actual shape and plots all clarity features on the diagram. The grader verifies information regarding the diamond’s measurements and weight and then assigns the diamond specific values for clarity, polish, and symmetry. Next the grader provides written descriptions of the diamond’s culet and girdle thickness. All of the grader’s observations are entered into a GIA software system where diamonds are only known by their GIA identifiers; they are not associated with any particular client.
A second diamond grader independently repeats all of the first diamond grader’s steps. At the end of inspection, all information is compared, though not by the same two graders to eliminate any bias.
In some cases, senior staff members are requested to make additional independent evaluations. These requests are triggered by a diamond’s weight, quality, and differences in the first two grading opinions.
Grading Diamond Color
All diamonds are evaluated for color in a standardized viewing environment. At least two color graders evaluate the diamond without knowledge of each other’s opinion. Additional color graders are asked for their independent color opinions, depending on the agreement of the first two assessors as well as the diamond’s carat weight and overall quality.
Grading Diamond Cut
A GIA cut grade is assigned, taking into account the diamond’s clarity and color evaluations, measurements of facets and their angles, and descriptions of polish and symmetry. Other considerations include the diamond’s weight, durability, and scintillation, the sparkle and pattern as light hits the diamond. The GIA only provides a cut grade for standard round brilliant diamonds with color grades from D to Z.
Can I send my diamond to a gemological laboratory for testing and certification?
Yes, anyone can send a diamond for evaluation and certification.
Gemological Institute of America (GIA)
The GIA performs evaluations and certification for loose diamonds at several international locations. Patrons download, complete, and include a contract with their shipment. Diamonds in the United States of America of four carats or smaller should be sent to their Carlsbad, California, laboratory; larger diamonds and fancy color diamonds should be sent to their New York laboratory. A 1-carat diamond sent to the California GIA laboratory can have a full GIA Diamond Dossier or GIA Diamond Grading completed within three to five days. The additional time spent shipping the diamond to and from the lab depends on carrier method. Diamond Dossiers are prepared for loose diamonds with color grades of D to Z. The fee is based on the diamond’s carat weight; a one-carat diamond’s GIA Diamond Dossier costs $90. All GIA Diamond Dossiers include the inscription of the GIA report number at no additional charge. A GIA Diamond Grading Report for a one-carat diamond costs $100.
Diamonds can be reexamined after a new cut for a smaller fee. A reexamination of a specific grade (color, cut, clarity, polish, symmetry, etc.) is available within 60 days of an examination, at a reduced cost.
The GIA also offers diamond inscription services. For a one-carat diamond, the report number can be inscribed for $15, and other graphics or words can be inscribed at $19 for the first 15 characters and $15 for each additional character.
More information is available on the GIA Web site.
International Gemological Institute (IGI)
The IGI asks patrons to mail their diamonds for certification to their New York location. Fees and other details on how to request a certification are not found on the Web site. Individual patrons can request information using the IGI Online Live chat feature. Fees are based on total carat weight and the type of gem. Certification for a one-carat, loose diamond was quoted as $65 (October 2008).
American Gemological Society (AGS)
AGS only offers diamond grading to members of the jewelry industry.