Every diamond is the unique product of heat and pressure over billions of years. So, how is one different from another and how do you determine its value?
The Gemological Institute of America (GIA) created the globally accepted standard of diamond grading, commonly known as the four C’s: Cut, Color, Clarity, and Carat. Creating a standard for diamond grading makes it easier to determine the value of each stone.
Here is what you should know about the four C’s and how to apply them to your buying process.
When you think of a diamond cut you probably think of the shape (round, princess, etc.), but the cut grade is so much more than that. The cut grade is about how well the facets interact with light.
There are three subcategories that make up a diamond’s cut grade according to GIA: proportions, symmetry, and polish. Cut grades range from Excellent to Poor for round brilliant cuts. Fancy shaped diamonds like princess or cushion cut often have polish and symmetry grades, but there is no set standard for ideal proportions on fancy shaped stones like there is for round brilliant cuts.
Of the four C’s, the cut grade is the most challenging characteristic to evaluate and grade.
Diamond graders view light return in three different forms:
- Brightness: White light reflected from a stone.
- Scintillation: The balance of light and dark patterns within a stone due to reflections within the stone.
- Fire: The scattering of white light into all colors of the rainbow.
A cut grade also takes into consideration stone depth, girdle thickness, facet symmetry, and the quality of polish on the facets.
Color grading for most gem-quality diamonds is based on the absence of color. You measure colorlessness on a letter scale ranging from D color (completely colorless) to Z color (light color). A grader will evaluate the stone under controlled lighting conditions and compare to masterstones to determine the color grade of a stone.
*Keep in mind, Fancy Colored Diamonds, like Fancy Yellow or Brown are on an entirely different color scale*
Clarity is the absence or presence of inclusions or blemishes in a gemstone. Inclusions are commonly referred to as flaws in the diamond, but this is a little misleading. Internal inclusions and external blemishes are created during diamond formation.
Diamond graders determine clarity grade by evaluating the types, size, position, and number of inclusions or blemishes in a stone. The closer a diamond is to perfectly pure, consequently the more rare and valuable it is.
Clarity grades range from Flawless (F) to Included (I1, I2, I3).
Carats are a unit of measurement for a diamond. Specifically, a “carat” is 200mg. Carats are divide into 100 units or points and measured to the hundredths place, for example 1.52 carats.
Two diamonds of the same weight can have very different values depending on clarity, cut, and color. Also, pricing jumps exponentially when the size hits certain “magic” numbers like 1.00, 1.50, and 2.00 carats.
The four C’s combined establish a standard for determining diamond value. The true value is creating a memorable experience when you purchase a diamond or give one as a gift.