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Diamond Grading: the Four Cs

Investigate the 4 Cs of diamond grading, diamond carat weight, diamond clarity, diamond color and diamond cut to help you buy the best diamond for you.

By Christopher Clark, GG, FGA, ASG, Gemologist & Co-Editor of The Sisk Gemology Reference | JTV
Published: 04/01/2011
Modified: 11/01/2020
diamond diamond-carat-weight diamond-clarity diamond-color diamond-cut
Diamond Grading: the Four Cs
Table of Contents
  • Diamond Carat Weight
  • Diamond Clarity
  • Diamond Color
  • Fancy Colored Diamonds
  • Diamond Cut

Most people have heard about the four Cs of diamonds through advertisements or direct contact with jewelry salespeople. However, while familiar with the concept, most individuals are a little sketchy on the details. The four Cs include diamond carat weight, clarity, color and cut.

Diamond Grading: The 4 Cs (source: Gemstones.com YouTube)

Diamond Carat Weight

Carat weight is pretty black and white. Diamonds are weighed in carats, which are composed of 100 points. Basically, a half-carat stone is 0.50 carats or 50 points. Carat is abbreviated as "ct." Special diamond scales calibrated to one thousandth of a carat are generally used in the jewelry trade, so diamonds are weighed to the thousandth and rounded to the hundredth of a carat. Occasionally you may hear the term "four grainer" referring to a 1-carat stone. Each grain is equal to 0.25 carat or 25 points. If you think in terms of grams, 1 gram is equal to 5 carats. This metric equivalency provides a level of uniformity anywhere in the world.

Due to the limited supply of larger diamonds, the value of a diamond rises disproportionally as the weight of the stone increases. For example, four 0.25-carat diamonds of the equivalent quality will not equal the value of a single 1-carat stone of identical quality. The disparity becomes more noticeable as the size and quality of the diamond increases.

brilliant cut brown diamond gemstone
Brown Diamond

Diamond Buying Tip: Note that "carat" describes the weight of a stone, not the size. Carat weight and size are fairly uniform from diamond to diamond so a 1-carat round diamond will consistently measure around 6.5 mm. (Colored stones, however, are a different story. Since density varies from one gemstone to the next, shape and dimensions must be specified. If you are ordering a colored stone for your favorite 1-carat round diamond semi-mount, then you also need to specify 6.5 mm for the size. Standardized calibrations were created for gemstone and jewelry manufacturing.)
Unboxing Rough Diamonds | Freeform, Macles

Diamond Clarity

Clarity is determined by the type, size, number, position and contrast of inclusions. Contrast is important, because dark inclusions in a diamond are more visible and therefore more distracting from a diamond's beauty than white or gray inclusions. Plus, if an inclusion is positioned in just the wrong spot, it can be reflected within the stone multiple times, making the diamond appear even less attractive and negatively affecting its clarity even more. Inclusions occur within the stone, while blemishes are external in nature. There are many grading scales used to describe diamond clarity; however, the diamond grading scale used by the Gemological Institute of America (GIA) is probably the most well known. The scale can be broken down as follows:

Flawless (no inclusions under 10x loupe)
IF (internally flawless, surface blemishes exist)
VVS 1, 2 (very, very slightly included: minute inclusions)
VS 1, 2 (very slightly included: minor inclusions)
SI 1, 2 (slightly included: noticeable inclusions)
I 1, 2, 3 (included: observable inclusions)

Diamond grading should always be performed with a 10-power (10x) loupe or microscope under proper lighting by a trained gemologist. Inclusions in stones graded I1, I2, and I3 can be seen by the unaided eye.

Note: In some cases the term "imperfect" will be substituted for "included" when describing VVS, VS and SI stones. Diamonds in the I range are also sometimes referred to as imperfect 1, 2 or 3.

large uncut diamond specimen
Diamond Specimen

Diamond Buying Tip: Clarity makes a significant impact on the price of the stone, but when shopping for diamonds, you should remember that clarity does not always significantly affect a diamond's brilliance and better clarity does not always ensure a more brilliant stone. While clarity does affect a diamond's brilliance, the stone's cutting largely determines its brilliance. In fact, most people cannot discern the visible difference between diamond clarity grades “flawless” through “slightly included.”

Diamond Color

Color grades, using the GIA scale, ranges from D to Z, with D being colorless and Z being heavily (usually yellow) colored. Colorless stones (designated D, E or F) command the highest prices. Diamond colors rank in the following groups:

Colorless: D, E or F
Near Colorless: G, H, I or J
Faint Yellow Tint*: K, L or M
Very Light Yellow Tint*: N, O, P, Q or R
Tinted Light Yellow*: S, T, U, V, W, X, Y or Z

* The tint viewed may actually be yellowish, brownish or gray.

When grading diamonds, a nonreflective white background should be used. Diamond graders have to be careful about the surrounding environment. Clothing color, lighting and the color of their instruments may affect the outcome.

All About Black Diamonds (source: Gemstones.com YouTube)

Fancy Colored Diamonds

Diamonds of certain colors are called fancies. These colored diamonds have intense natural colors that in some cases are very rare and command exceptional values. These stones are not color graded using the scale above. Brown and yellow diamonds are the most common members of the fancy diamond group and have a distinct beauty of their own. Naturally red, blue, purple and green diamonds are extremely rare and highly sought after by designers and collectors.

multiple shapes and sizes of green diamond gemstones
Green Diamonds

Diamond Buying Tip: Color is one of the most noticeable characteristics of a diamond. Most people can notice whether or not a diamond is colorless (the most desired). The setting of the diamond can affect the appearance of color. If the diamond is colorless, a white gold or platinum setting will enhance the diamond's whiteness. But if the diamond has a yellowish tint, a yellow gold setting may help mask the yellow tint, making the diamond appear whiter.

Diamond Cut

The breathtaking beauty of a diamond comes from a combination of fire (that flash of rainbow colors that comes from within) and brilliance (the burst of sparkling light). This dazzling beauty is a direct result of the diamond's cut. The last of the four Cs, cut is a little more complicated than just the shape or visible outline of the diamond. Cut also refers to a diamond's faceting as well as the diamond's symmetry, proportion and finish (known in the trade as the "make").

There are three basic styles of diamond faceting: brilliant cut, step cut and mixed cut.

Brilliant: Designed for maximum diamond sparkle, the brilliant cut uses many triangular and kite-shaped facets.
Step: Instead of sparkle, a step cut aims to increase a diamond's elegance with fewer facets and more trapezoids and rectangles.
Mixed: A mixed cut combines the step and brilliant cut styles for a uniquely beautiful diamond.

All diamonds are cut to certain tolerances designed to maximize the play of light within the stone. If the stone varies too greatly from the accepted standards, light is lost through bottom or sides, reducing the diamond's liveliness and overall beauty. As a general note, most full-cut round brilliant diamonds have either 57 or 58 facets, depending on the absence or presence of a culet (the bottom-most facet or "point" of a stone).

multiple shapes and sizes of red diamonds
Red Diamond

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Christopher Clark

About the author

Christopher Clark

A Graduate Gemologist and Fellow of the Gemological Association of Great Britain, Christopher has spent the last 4 years co-editing The Sisk Gemology Reference. He also acts as a customer advocate by inspecting and testing gemstones as they come into Jewelry Television to ensure they are exactly what our customers expect. He is an avid collector of vintage jewelry, gemstones, mineral specimens and spheres. Employed at Jewelry Television since 2006, Christopher spends much of his time immersed in the fascinating world of jewelry and gemstones.

Christopher’s passion for collecting valuables and precious stones began when he was shopping at a retired jeweler’s garage sale and he purchased a parcel of colored gemstones and a “lump of metal” that turned out to be GOLD! From that moment forward, the treasure hunt was on! But occasionally, he does become a commodities trader as he keeps an ever-watchful eye on precious metal prices. Unfortunately for his wallet, though, most of the treasures he acquires are never resold as they simply get added to his ever-growing collections. Christopher especially enjoys collecting vintage pocket watches and Mexican antique silver jewelry.

Christopher is now an Accredited Senior Gemologist with the Accredited Gemologists Association. He volunteers his time with a local gemological society for identifying gemstones. Christopher is always excited to attend major gemstone trade shows and is always on the look-out for the next great gem to bring JTV customers. Working closely with our vendors, Christopher has built a business rapport with them that allows for an easy trust and mutually beneficial working relationship. His favorite gem? Without a doubt, OPAL!

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