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.
“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”
“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.
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.