No two diamonds are exactly the same. So how do we differentiate between diamonds and ultimately assign value?
The Gemological Institute of America created a system that is consistent and reliable to determine the rarity of a stone based on common measures. These common measures are called "The 4Cs".
Diamond Differentiation: "The 4Cs"
The 4Cs are made up of Carat, Color, Clarity, and Cut. The rarity of a diamond's combined 4C characteristics will determine the value of a diamond.
Carat:
“I never worry about diets. The only carrots that interest me are the number you get in a diamond” - Mae West
“Carat” is the unit of weight measurement used for diamonds and other gemstones.
The term "carat" goes back to ancient trade routes where a standard weight was needed for precious gems. Seeds and grains found along the routes were used as widespread accepted units for counter measurement to gemstones on the scale. It is believed “carat” derives from carob seeds (“quirat” in Arabic), which have low variability from one seed to the next. This meant that two traders could agree upon the weight measurement of an item and ultimately a value.
Two stones of equal weight can vary widely in price because of differences in the quality of the other three Cs. However, when considering diamonds that have all other characteristics as equal, the larger stone will have more value. This is because it is less common to find a diamond that has grown to be large and been able to stay intact throughout the long journey from the center of the earth to the surface, through the mining process, and being formed into a beautiful gemstone.
A few things to know about carats:
Carat is abbreviated “ct”
1 carat = 0.2 grams
1 carat is made up of 100 points (Think of pennies and a dollar with a dollar being 1ct and pennies being each point)
If a diamond is smaller than 0.18ct (18 points), it is referred to in the trade as “melee” (rhymes with belly), which are predominantly used as accent stones
If multiple diamonds are used in a piece, the total weight of the diamonds will be expressed as “carat total weight” or “ctw”
Color:
“The purest and most thoughtful minds are those which love color the most.” – John Ruskin
Carbon is one of the most common substances on the planet, however carbon in the form of diamonds is extremely rare. Being 99.95% carbon, diamonds are the purest natural substance. The other 0.05% of a diamond is made up of trace elements that are present in the environment while the diamond crystallizes deep within the earth. The most common trace element in a diamond is nitrogen, which gives diamonds a yellowish tinge, though other elements may exist causing other notable affects. For example, the presence of boron makes a diamond blue and allows it to conduct electricity!
For diamonds, color is defined as the relative position of a diamond’s body color on a scale of colorless to light yellow or brown. The Gemological Institute of America (GIA) has developed an industry standard for grading color on a scale of D-Z that ranks ‘D’ (colorless) through ‘Z’ (light yellow or brown). GIA has produced sets of “Master Stones” to which diamonds are compared to determine the exact color of a diamond.
Color Grading
On the Colorless Diamond Scale, the less color apparent in a diamond, the rarer and more valuable it is.
Grades D, E and F are considered “colorless”.
Grades G, H, I, J are “near colorless”.
For these grades, the main point of value is rarity. The color difference between a D, E, F and G, H, I is indiscernible to the untrained eye, however a diamond that is DEF is much more rare than GHI.
Grades K, L, and M are faint yellow.
Grades N, O, P, Q, and R grades are described as very light yellow.
Grades S - Z are light yellow
The type of light and color in the surrounding environment will affect how a diamond is seen. Therefore, to grade color, a diamond grader works in a color neutral environment with northern-daylight equivalent light source. You will never wear a diamond in a condition like this and so it's more important to consider how we are setting a diamond when we are determining what colors are "acceptable" for our purposes. The naked eye cannot discern color until we hit a K on the color scale (J, if you're really good!). A diamond in the DEF range will start to pick up the color of the metal, so yellow gold will make a DEF appear more yellow. A diamond with greater color will appear whiter if it is set in yellow gold due to the color contrast.
Diamonds are color graded with the face down in order to avoid the internal reflections seen when the diamond is viewed in the face-up position. Remember: Diamonds are cut to be sparkly and return white light to the eye! This white light will distort the color of the stone itself.
A diamond grader will move the diamond back and forth from one side of a master stone set to the other, looking to see if the diamond exhibits more or less color than the diamond to which it is being compared. When the color matches a master stone, then that is the color grade assigned.
Fancy Colored Diamonds:
Fancy Color? Oh la la! While most of us think of diamonds are being white or colorless stones, there are diamonds that exhibit beautiful, rich, saturated colors that are so spectacular they can only be referred to as “Fancy”.
Diamonds that fall on the “Fancy Colored Diamond Scale” are extremely rare. Each Fancy Colored Diamond is cut to maximize color saturation. Color is nuanced. Rather than grade “Fancy Colored Diamonds” on a linear scale as we do with Colorless Diamonds, Fancies are graded on a chart that evaluates hue, tone, and the intensity of saturation.
Hue:
The primary body color of the diamond. For Fancy Colored Diamonds, GIA has recognized 27 distinct hues (27!!!) and within each hue, there are many possible secondary colors that further describe the color of the diamond.
Tone: The lightness or darkness of the hue. (Example: Navy Blue has a darker tone than Sky Blue, but both are a blue hue)
Saturation:
This is the intensity of the color. You can also think of this as the colors distance from gray. A more vivid saturation has more pure hue, whereas a less saturated color appears to have more of a muted or gray appearance.
[SIDE NOTE: Fluorescence]
Though fluorescence is not one of the 4Cs, it can affect the color you see when looking at a diamond.
Fluorescence is naturally found in certain diamonds and many colored gemstones. When exposed to ultraviolet light, a gemstone with fluorescence appears to glow. This amazing effect is caused by the excitement of electrons that jump between atomic orbitals, releasing energy that we perceive as glowing light. In diamonds, we typically see fluorescence as varying degrees of blue light, though they can fluoresce in other colors as well. The Hope Diamond fluoresces red!
Fluorescence may be graded as None, Faint, Medium, Strong or Very Strong. A diamond with fluorescence graded “strong” or “very strong” can appear to glow in sunlight or appear cloudy or milky. In stones in the K-Z range, strong fluorescence can mask the color of the stone, allowing a yellowish stone to appear closer to colorless in natural light.
Clarity:
"Better a diamond with a flaw than a pebble without one." – Chinese Proverb
Clarity is the degree to which a diamond is free from characteristics that affect the transparency of a gem. Diamond Clarity is graded on a scale of “Flawless” to “Included 2” with the presence of clarity characteristics increasing from none present in “Flawless” to characteristics that are visible with the naked eye in an “Included” diamond. There are two types of clarity characteristics: Inclusions and Blemishes. Blemishes are characteristics that are confined to the surface of the diamond, such as scratches, abrasions, polish lines, and naturals, which is the presence of the diamond’s original rough that is left visible in the finished faceted gemstone. Naturals typically appear on a girdle and indicate that as much of the rough was used to fashion the final gemstone as possible. Inclusions are clarity characteristics that are found inside the gemstone. There are many types of inclusions, such as "Crystals", which are either diamonds or other gemstones that have formed within the larger diamond. These crystals can range in size and shape. When they are elongated, they are called “Needles”. Very small crystals are called “Pinpoints” and when there is a group of pinpoints that may create haziness within the stone, they are referred to as a “Cloud”. Sometimes inclusions can extend to the surface of the gem as a fracture or break, which is called a “feather”. If a crystal is found touching the surface of a diamond, it is called a “Knot”, which may fall out to create a “Cavity” in the diamond. A clarity characteristic may affect the beauty and/or durability of the diamond depending on the depth and position of the characteristic. A dark inclusion set right in the center of a diamond will have a greater affect than the same inclusion off to the side of the diamond because of the obviousness of placement.
When I look at clarity, I look to make sure the inclusions do not affect the beauty or durability of the diamond (ie: It's not glaringly obvious to the naked eye and the inclusion isn't going to cause the diamond to break during setting or wear).
Diamond clarity is graded with a loupe or microscope at 10X magnification. The clarity is graded based on how obvious the inclusions are when the diamond is viewed through the top facet.
There are five main considerations that a diamond grader takes into account while assigning a clarity grade:
1. Size: How large are the inclusions? Larger inclusions tend to be more obvious than smaller inclusions.
2. Number: How many inclusions are there? If a diamond has many inclusions and many types of inclusions, they will be more apparent.
3. Position: Where are they located? A blemish or inclusion located under the table is much more apparent and therefore will reduce a grade more than one located to the side of the stone or in the pavilion.
4. Nature: What type of inclusion is it? A large feather will have a more significant effect on the grade than a pinpoint in the same location, as a feather is more likely to distort the speed with which light travels through the diamond and therefore creates a disjointed appearance.
5. Relief: How much does the characteristic stand out against the background of the stone? This can happen if a crystal disrupts the transparency of the diamond or has a color that contrasts with the body color of the diamond, such as a gray or red crystal inclusion.
A clarity grade is determined by considering all of these factors, but it is ultimately determined by the characteristics that are most obvious. These are called the “clarity setting characteristics”.
Clarity Plot
The clarity characteristics are the fingerprint of the stone. No two diamonds have the same characteristics in the same locations--this is key in differentiating one diamond from the next. Diamond graders may create what is called a “Clarity Plot”, which is a map of the locations and nature of the grade setting characteristics. The plot can therefore be used to decisively identify a diamond.
CUT:
“The more the diamond is cut, the brighter it sparkles." – Thomas Guthrie
Arguably the most important of the 4Cs, Cut affects how beautiful the diamond will be. Cut will determine the shape, size, the location of clarity characteristics, and the way light interacts with the diamond’s angles, creating scintillating patterns and prismatic effects.
Diamonds have an incredible ability manipulate light in mesmerizing and delightful ways. A diamond’s cut determines how light interacts with the diamond, resulting in whether we see light as being sharp white sparkle, prismatic rainbows, or a watery and ethereal glimmer.
When thinking about light and diamonds, we consider three types of light: Brilliance, Dispersion, and Scintillation.
Brilliance is the return of white light to the viewer’s eye.
In a “brilliant cut” diamond, the facets on the pavilion (the bottom half of the diamond) act as mirrors. Light enters the diamond, illuminating the interior. The light will then reflect off the pavilion facets and exit the diamond through the top, returning to the viewer’s eye. Brilliance determines the brightness of the diamond and is controlled by lapidaries (stonecutters) who can cut a gemstone so that light enters and strikes the pavilion facets at critical angles to reflect light internally and out through the top flat facet.
Dispersion, also called “Fire”, is when white light, which is made of all colors of light, is broken into separate wavelengths of color.
Dispersion is caused by a gemstone’s density and the angles at which the facets are cut.
Different transparent materials cause light to travel at different speeds depending on the “optical density” of the material. This means when white light travels through air and then enters a diamond, the speed of the light changes. Changes in optical density cause light to bend or “refract”. If light bends at a sharp enough angle, the white light will break into the rainbow of wavelengths that make up white light. These wavelengths do not come back together, even when the wavelengths exit the diamond, which is how the eye sees different colors or “Fire".
Antique diamond cuts, such as the Old European Cut and Antique Cushion Cut, are known for their fire. The steep crown angle and small table facet cause light to enter the diamond at various angles and then bend and break repeatedly. The result is a beautiful, prismatic effect.
Scintillation, also called “Sparkle”, is light reflecting off of the surface of the diamond. Scintillation is most visible when either the diamond or the light source moves.
In a well-cut diamond, you will see Brilliance, Dispersion, and Scintillation simultaneously.
If a diamond is poorly cut, light that enters a diamond will leak out through facets other than the table on the top. This will result in a less lively diamond that lacks brilliance, fire, and sparkle returning to the eye.
The Three Characteristics of Great Cut:
Make:
Make is the quality of how a diamond is fashioned. This reflects a diamond cutter’s level of skill. The shape, size and angle of each individual facet are crucially important.
Symmetry:
Symmetry refers to how well the cut is proportioned. A diamond that demonstrates good symmetry will have a balanced and even layout of facets.
Polish:
Polish is how smooth the exterior surface is finished. Imagine a window that is cleaned, but streaks are left on the glass. These streaks will change how well you see through the glass and will block light from coming in. This is also true of diamonds that have not been polished well. A diamond’s high polish grade helps ensure that a diamond’s beauty is accentuated and not compromised.
While the Carat, Color, Clarity, and Cut of a diamond may allow for placing a value on a diamond through the establishment of consistent and common measures, the 4Cs are not the end-all, be-all in evaluating a diamond.
While two diamonds may have the same 4Cs delineated on a diamond report or certificate, every diamond is one-of-a-kind. The unique snowflake of inclusions and the hand-wrought faceting will give each diamond a unique personality.
Though a certificate can provide a lot of information, the certificate does not and cannot tell you if the diamond is a beautiful diamond. The certificate also cannot tell you if any of the inclusions present compromise the durability of the diamond.
For this reason, a truly skilled gemologist will first look at a stone with his or her eyes, rather than at the certificate. A good gemologist will always prioritize beauty and durability over every other factor.