The American Gem Society (AGS) and Gemological Institute of America (GIA) have precise standards for evaluating diamonds, commonly known as the 4 C’s. Leber Jeweler has added “Country of Origin” to our list of factors. Understanding this “science of diamonds” takes the fear out of selecting that perfect stone.

Cut

Of all the criteria used to assess diamonds, cut is the most obvious one to the naked eye. The cut of a diamond is what gives a stone its brilliance and sparkle. But don’t confuse cut with shape. To a gemologist, the term cut refers to how efficiently light is transmitted through a gem, based on an ideal set of proportions, as shown here.

Cut is one of the most overlooked qualities of diamonds. Of the recognized laboratory diamond certificates, the American Gem Society (AGS) Report assigns a specific cut grade to a brilliant-cut stone. Like all AGS grading standards, the scale is divided between 0 and 10, with 0 being the best. The Gemological Institute of America (GIA) uses a five tier system with diamonds graded as Excellent, Very Good, Good, Fair and Poor.

Avoid any diamond that uses superlatives like “super ideal” or “hyper ideal” or “mega ideal.” These are all marketing terms and are not recognized by any legitimate gem expert.

How do such practices affect consumers? If you compare two stones that are equal in all grading areas except for cut, the stone with the superior cut could cost as much as forty percent more than the lesser-cut diamond. A trained gemologist considers at least eight factors when evaluating cut, including a stone’s major proportions, polish, and symmetry.

Color

To grade color, a gemologist compares the body color of a diamond with a set of Master Comparison Diamonds under specific light conditions. Newer techniques are finding their way into the marketplace, but this method continues to be a highly accurate and consistent means of grading diamond color.

AGSElectronic ColorimeterGIA

00 to 0.49D
0.5.50 – .99E
1.01.0 – 1.49F
1.51.50 – 1.99G
2.02.0 – 2.49H
2.52.50 – 2.99I
3.03.0 – 3.49J
3.53.50 – 3.99K
4.04.0 – 4.49L
4.54.50 – 4.99M
5.05.0 – 5.49N
5.55.50 – 5.99O
6.06.0 – 6.49P
6.56.50 – 6.99Q
7.07.0 – 7.49R
7.57.50 – 7.99S
8.08.0 – 8.49T
8.58.50 – 8.99U
9.09.0 – 9.49V
9.59.50 – 9.99W
1010 – +XYZ

The A.G.S. and the G.I.A. have similar grading scales with the following values for diamond color:

0Absolutely colorless and transparent.
1Colorless, somewhat less transparent.
2Very faint yellow; appears colorless to the customer.
3Appears colorless if set in gold jewelry.
4 Color is visible to the novice.
5–10Increasingly easy to see color.

Clarity

Clarity is the most tangible factor in the diamond-grading process. Clarity is a measurement of the relative number, size, nature, and position of inclusions within a stone. These flaws may include “feathers,” separations caused by fractures, crystals, minerals, or any number of features that occur naturally when diamonds are formed.

Unfortunately, clarity has become the most abused grading aspect. Many jewelers, diamond sellers, and lesser known gem laboratories do not grade with the same rigid standards as the American Gem Society and Gemological Institute of America laboratory standards. While they may present a diamond as a specific grade using either the AGS or GIA grading system, it is important for the purchaser to verify that the represented grading of a stone be in keeping with AGS or GIA laboratory standards. Many diamond sellers consider grading a diamond with less stringent standards (resulting in a higher grade) “defensible”, we consider it wrong.

The A.G.S. and G.I.A. grading scales for clarity are similar, as indicated below.

AGSDescriptionGIA

0No inclusions or blemishes of any sort when examined by a skilled grader under 10x magnification and proper lighting.Flawless
0
with a comment
No inclusions of any sort and only minor blemishes when examined by a skilled grader under 10x magnification and proper lighting. Typical comments include: “Minor details of finish are not shown.” “Surface grain line is not shown.”Internally Flawless
1Contains minute inclusions that are extremely difficult for a skilled grader to see under 10x magnification.VVS1
2Contains minute inclusions that are very difficult for a trained grader to see under 10x magnification.VVS2
3Contains minor inclusions that are somewhat difficult for a trained grader to see under 10x magnification.VS1
4Contains minor inclusions that are somewhat easy for a trained grader to see under 10x magnification.VS2
5Contains noticeable inclusions that are easy for a trained grader to see under 10x magnification.SI1
6Contains noticeable inclusions that are very easy for a trained grader to see under 10x magnification.SI2
7Contains inclusions that are apparent under 10x magnification and often visible to the unaided eye.I1
8Contains inclusions that are obvious under 10x magnification, are usually easily visible to the unaided eye, and may affect the durability.I1
9Contains inclusions that are very obvious to the unaided eye and may affect the durability.I2
10Contains inclusions that are very obvious to the unaided eye and pose a definite threat to the diamond’s durability.I3

Inclusions and marks in diamonds at grades 1 and 2 are difficult to see under 10x magnification. Grades 3 and 4 present less difficulty. In grades 5 and 6 the marks are readily seen under magnification, but they may be invisible to the naked eye when the stone is face up. In grade 7, one or more inclusions are visible to the unaided eye. Grade 8 contains easily visible inclusions, and grade 9 has inclusions so obvious and large that they affect both the brilliancy and beauty of the diamond. Grade 10 includes diamonds with a shattered appearance or with disfiguring and dangerous inclusions and surface marks.

Note: The GIA grade IF (Internally Flawless) cannot by definition be an AGS grade. IF is usually the equivalent of AGS grade 1, but in certain instances it could be lower.

The most obvious line of distinction in clarity grading occurs between AGS grades 6 and 7 (GIA SI2 and I1). From Grades 7 to 10, inclusions are obvious under 10x magnification and are visible to the naked eye. Grades 6 and 7 are also seem to be the areas in which discrepancies involving diamonds with less recognized “certs” occur.

Inclusions and marks in diamonds at grades VVS1 and VVS2 are difficult to see under 10x magnification. Grades VS1 and VS2 present less difficulty. In grades SI1 and SI2 the marks are readily seen under magnification, but they may be invisible to the naked eye when the stone is face up. In grade 7, one or more inclusions are visible to the unaided eye. Grade I2 contains easily visible inclusions, and grade 9 has inclusions so obvious and large that they affect both the brilliancy and beauty of the diamond. Grade I3 includes diamonds with a shattered appearance or with disfiguring and dangerous inclusions and surface marks.

The most obvious line of distinction in clarity grading occurs between GIA grades SI2 and I1, although many SI2 diamonds will have some eye visible inclusions that may be visible to the unaided eye.

Carat Weight

The most literal and easily understood of the “four C’s,” carat weight is measured instead of graded. The carat is a standard of measurement equal to 200 milligrams, or one-fifth of a gram.

The weighing of a diamond usually takes place on an Electronic Balance and is measured to the nearest point (.01).

Other Aspects

Country of Origin  
In the world’s rapidly changing political climate, there is a fifth C to consider. Much of the world’s diamond supply has its origins in some of the most politically troubled and frequently impoverished nations on the globe. With many of these countries embroiled in long-going internal conflicts, diamonds have historically been used (like most other natural resources) to help fund these conflicts. While the Kimberly Process has made tentative steps to stem this illicit trade, it is far from perfect and only Canada currently offers valid documentation of country of origin for diamonds.

Clarity Enhancement  
There are forms of treatment used by some diamond sellers whose goal is concealing inclusions or minimizing the effects of body color in a stone. If a diamond has been enhanced in any way, the seller is required by law to give full disclosure to the customer at the time of sale.

Laser Drilling and Fracture Filling 
These are two of the most common methods of disguising inclusions. Laser drilling is used to lighten visible inclusions in diamonds. A laser beam cuts into an inclusion, then a bleaching chemical is fed into the opening to change the inclusion from light to dark. This process is generally found in lower quality stones with clarity grades ranging from 6 to 9. While the Federal Trade Commission extends every effort to protect the consumer from fraudulent business practices, it is currently not required to disclose laser drilling in diamonds at this time.

Fracture filling is generally used to conceal feathers that are highly reflective and visible. The process requires that the feather must open to the surface of the stone. In a vacuum environment, the air is removed from the inclusion and is replaced with a substance that has a high refractive index. Since the optical properties are similar to the diamond, the filling—and the feather—are minimized.

Color Enhancement  
Research firms are developing techniques to minimize body color in diamonds. We will provide more information about this type of enhancement as it becomes available.

Although the Federal Trade Commission requires full disclosure of many types of enhancement, many jewelers and online diamond sellers do not have the specialized knowledge or gemological training needed to recognize the characteristics that indicate enhancement.