Education:Understanding Diamonds

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 looks 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.

Cut

More than any other factor, the cut or "shape" of a diamond will determine its brilliance or sparkle. 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 cut will cause light to escape from the bottom causing a dull or dark appearance. An ideal cut has the appropriate proportions that cause light to be reflected back through the top.

Round Brilliant Cut Diamond DiagramTable 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 shaped. Note: the round cut is designed to reflect the most light and thus gives the most brilliance.

Carat

Carat Weight ChartCarat refers to the weight of the diamond, but is often confused with its "size". One carat equals 200 milligrams.

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

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

Diamond Clarity ChartClarity

When light enters a diamond, any imperfection can affect its flow, and 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.

The clarity scale from flawless (FL) to included (I) is based on visibility at a magnification of 10X. The lower the associated number, the higher the quality in that range (e.g., VVS1 is the highest VVS quality).

The location of an inclusion can also influence its impact on a diamond's brilliance.

Color

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 commonly found diamonds are in the range of colorless (D) to yellow (Z). Diamonds outside this range are termed fancy colored.

Color differences are very subtle. Most people would have a hard time distinguishing between two diamonds, one rated F and one rated G. Thus, color comes down to personal taste. Colorless diamonds and rare fancy colors are the most valuable.
See the above chart for an illustration of the color ratings.