Diamond Education

The Basics:
The first step is to understand how to compare one diamond to another. To help you with this comparison, the Gemological Institute of America (GIA) developed a standardized grading system for diamonds. This universally accepted grading system is referred to as the Four C's: Cut, Carat Weight, Clarity, and Color. At Diamonds of Palo Alto, all our diamonds come with GIA certifications.

The Four C's of Diamonds:
Light is the common element that gives diamonds their brilliance and luster. Its interaction with each of the Four C’s will determine why one diamond will look more brilliant than another.

When taken together, the Four C’s give a diamond its unique personality. They provide a precise index of a diamond's comparative rarity, quality, and value. Remember though, that beauty is in the eye of the beholder. A diamond's official grade might not represent the beauty seen in it by its owner.


The cut or “shape” of each diamond will determine its brilliance or sparkle more than any other factor. This is the only one of the Four C’s that can be influenced by the human hand. As with the other “C’s”, how light interacts with the Cut will determine its brilliance and ultimately its value.

While there are over 53 symmetrical cuts on a diamond, the two that are commonly used for comparison represent depth and width. A cut that is too shallow will cause light to escape out the sides while a deep will cause light to escape out the bottom causing a dull or dark appearance. More information is here about diamond cut. An ideal cut has the appropriate proportions that cause light to be reflected back through the top. If all of the facets are correctly positioned on a diamond then a pattern of perfectly optical symmetry and be viewed using a special viewer called Hearts and Arrows.

Table Width in proportion to Girdle Width will also influence how light is reflected and thus, the brilliance of a diamond. The Gemological Institute of America considers a Table Width in the range of 53% - 64% of Girdle Width to be Optimal for round stones. At Diamonds of Palo Alto, our diamonds have a Table Width of 54%-59%.

Cut also refers to the shape of the diamond –round, marquise, emerald, princess, pear, oval or heart. Note: the round cut is designed to reflect the most light and thus have the most brilliance.



Carat refers to the weight of the diamond, but often confused with its “size.” One carat equals 200 milligrams.

Because light has to travel farther within a heavier diamond, creating a prism effect, it will appear more brilliant than a lighter one.

Since heavier diamonds are more rare, the price of a diamond goes up as carat weight increases.

When light enters a diamond, any imperfection can impact its flow, thus its brilliance. These imperfections are called inclusions if found on the inside or blemishes if found on the surface. Most imperfections cannot be seen with the naked eye unless magnified.

The clarity scale from flawless (FL) to included (I) is based on the visibility at a 10X magnification. The lower the associated number, the higher the quality in that range (Ex. VVS1 = the highest VVS quality). For more informaiton and diamond clarity and to see how how the different clarity ratings appear under magnfication please watch this educational video on diamond clarity.

The location of an inclusion can also influence its impacts a diamond’s brilliance.


Like a prism, a diamond can cause light to divide into a wide range of colors. In fact, relatively few diamonds will actually appear colorless. Most diamonds commonly found are in the range of colorless (D) to yellow (Z). Diamonds outside of this range are termed fancy colored.

Color differences are very subtle. Most would have a hard time distinguishing between two diamonds with ratings of F and G. Thus, color comes down to personal taste. To see a comparision of how diamond colour affects the different diamond color ratings click this video about diamond color. It is also important to note that Colorless diamonds and rare fancy colors are the most valuable.
See the chart above for an illustration of the color ratings.



Diamonds of Palo Alto • 261 Hamilton Avenue, Suite 320 • Palo Alto, California 94301 • USA
800.444.9912 toll free • 650.322.1200 phone • 650 322 0228 fax
email: diamonds@diamondsofpaloalto.com