Valuing a diamond is a complex and nuanced process that requires a trained and experienced gemologist. First a diamond is graded, then its value is assessed based on the current diamond market. Below we outline how a diamond expert values a stone and which factors they take into consideration.
HOW A DIAMOND IS GRADED
The Four C’s:
Arguably the most important of factors, the 4 C’s are the core characteristics of your stone and the first thing that will appear on a diamond grading certificate.
- Carat Weight: Carat weight is directly correlated to the price of your stone (diamond price= price per carat x carat weight), and simply refers to the weight of the diamond. Of course the price will change based on other factors, but it is one of the first measurements taken. The abbreviated form of carat is ct.
- Clarity: The clarity is the presence, or absence, of flaws in a diamond. What may be visible to a GIA trained gemologist, might not always be visible to the untrained eye. Clarity grades range from FL (flawless) to I3 (imperfect).
- Cut: This refers to how the diamond was cut and its proportions, which affect how a diamond sparkles and its value. Cut grades range from Excellent to Poor.
- Color: The presence or the absence of color in your diamond. For white diamonds, the less color in the stone, the better. The opposite is true for fancy colored diamonds. Color grades for white diamonds run from D (colorless) to Z (light yellow).
When selling your stone to a diamond buyer, you will need to provide the 4 C’s in order to receive an initial price. Bear in mind that in order to receive a final price, a diamond buyer will need to examine your stone to verify these gradings as well as the other factors that go into pricing.
Beyond the Four C’s:
While the 4 C’s form the foundation of your stone’s value, there are other factors taken into consideration. The following categories also affect the value of your diamond.
Fluorescence refers to how a diamond reacts to ultra violet light: diamonds that fluoresce under UV light are lower in price. The reason for this is that the presence of fluorescence in your stone will sometimes make it appear hazy, as opposed to crisp and clear. Fluorescence grades range from None to Very Strong.
A diamond is polished with a polishing wheel, smoothing the stone’s surface. Sometimes however, during the polishing process, the wheel can drag dislodged crystals across its surface creating microscopic details which in turn damage the polish of the stone and take away value. Polish grades range from Excellent to Poor.
The symmetry of a diamond describes how well the facets are shaped and how symmetrical they appear. Facets are the flat geometrical shapes that you see on your diamond, each reflecting light and adding to the value of your stone if they are well placed. The higher the symmetry grade of your stone, the more valuable it will be. Symmetry grades range from Excellent to Poor.
There are three different properties that make up a diamond’s proportion:
- Brilliance: Refers to the amount of light that is reflected from your diamond. The more light that is reflected, the more value there is.
- Dispersion: As light flows through the diamond, some of it is separated into flashes of color. These flashes of color are called dispersion.
- Scintillation: Scintillation is the color that flashes when you move a diamond back and forth.
The anatomy of a diamond is the basic structure of the stone.
This structure determines the diamond’s proportions, including brilliance, dispersion, and scintillation. The main components are the diameter, crown height, girdle, table width, pavilion depth, and culet. In diamond valuation, there are certain proportional values that need to be achieved by each component to reach maximum value.
There are a variety of diamond treatments available that aim to counteract specific imperfections in a stone. Though this could help the value when selling a diamond at retail, people who are buying diamonds secondhand would rather have a natural stone. While diamond sellers are obliged to let a buyer know if a stone has been altered, it is not always guaranteed. Because of this, it is important to have a GIA certificate for your stone as it will have a record of any enhancements (assuming that the stone has not been altered since certification).
- Color Enhanced: Coating is a well-known, temporary color enhancement that involves placing a thin layer of chemicals over the stone and can be removed with acid. HPHT is a permanent color enhancement that involves putting the diamond under high pressure and high temperature. Another permanent technique is irradiation, which uses radiation to modify a stone’s color.
- Clarity Enhanced: A temporary clarity enhancement is fracture filling that hides cracks in the stone and can be removed by boiling the stone in acid. Laser drilling is a permanent option, and involves drilling a small hole and bleaches away the inclusions.
HOW A DIAMOND IS PRICED
Once a diamond has been evaluated, its value will be based on the current diamond market. After analyzing the current diamond market (supply and demand, trends, how similar diamonds are selling etc.), a gemologist will be able to price the stone. When selling on the secondhand market, this typically ranges between 20%-50% of retail price. WP Diamonds has an excellent guide on this subject.