What makes a good Diamond good?

Diamonds are forever.

Diamonds are a girls best friend.

A diamond in the rough.

These are just a few of the phrases we hear regularly featuring diamonds that hint at the value of a diamond. Diamonds are indeed beautiful: sparkly, shiny, glittering, scintillating gems that seem to catch fire when held under the light. They adorn our rings, our necklaces, our earrings, pendants, broaches, watches, bracelets, even cuff-links, tie-pins, spectacles, and accessories. We put them on anything we can to show that we love someone, that we have “made it”, or that we have sophisticated taste and style. They are symbols of love, wealth, prosperity, and style.

But what is a diamond, exactly, and why are some SO MUCH MORE EXPENSIVE than others? When I go to Zales or Helzberg or Kay or Jared, why is one diamond affordable and another so far out of my price range that it hurts to even look at it? Why are some jewelry pieces bunched close together, and some separated from the others and placed on a cushion or pillar?

As with just about everything else, some diamonds are “better” than others. That overall “better” quality is made up of four individual qualities referred to as the 4Cs: Cut, Clarity, Color, and Carat Weight. These quality standards are recognized globally and were established by the Gemological Institute of America, or the GIA, and together help determine the value of a stone.


The cut of a diamond is one of the most important qualities - if not the THE most important quality - in determining the value of a stone. The shape or cut of a diamond is what gives a diamond that sparkling fire that draws the eye and mesmerizes. Many cut shapes are available to the buyer, but some are more popular - and more valuable - than others. These shapes include: round, square, rectangle, octagonal, oval, marquise, pear, heart, and triangle. Some will carry names such as ‘round brilliant’, princess cut’, ‘pillow’ or ‘cushion’, ‘emerald’, or ‘asher’ cuts.

What is important about the cut is that this is what affects the sparkle the most. Without going into too much detail (a subject for a later post!), the sparkle is caused by light entering the diamond and reflecting off what are called the ‘facets’ or the many surfaces of the diamond. The light then exits back out the top of the diamond and is split by the top facets, like a prism. If the gem is cut precisely to the correct proportion and symmetry then the fire will be its brightest and most colorful. Also, the cut is the one and only quality of a diamond that the craftsman has any control over. The other three qualities are all determined by nature during the formation of the stone.


Color is probably the second-most important factor or quality in determining the value of a diamond. Actually, it is the LACK of color that makes a diamond more valuable. The GIA color grading scale grades a stone from D, being the most valuable, to Z. The D-end of the scale is called a white stone, while stones toward the Z-end are yellow. Chemical purity and level of structural perfection determine how colored or colorless a diamond is. Again, this scale from the GIA grades diamonds from colorless to yellow. Blue diamonds, pink diamonds, chocolate diamonds, do not fall into this scale. We’ll discuss them in a later post.


Next in line is clarity. Clarity indicates how ‘clear’ a diamond is. A diamond forms over a long period of time. Carbon is exposed to tremendous pressure and intense heat deep in the earth. This process leaves behind imperfections both inside the stone and on its surface. The internal imperfections are called ‘inclusions’ and the surface imperfections are called ‘blemishes’.

The scale for clarity runs from FL, which indicates a ‘flawless’ stone with no visible inclusions or blemishes, to I3, which indicates stones with obvious inclusions and blemishes. These inclusions and blemishes can affect color and brilliance, so the more or the larger the flaws the less valuable the diamond will be.

Carat Weight

Carat weight is just that: the weight of the diamond. Some people confuse carat weight with size. While size can generally be guessed by the carat weight, it is explicitly a unit of weight. This one is the easiest to determine for the untrained. All we have to do is stick it on a scale and, voila! We have the weight.

What is a carat, though? A metric carat is defined as 200 milligrams, or two grams. A 1-carat diamond will weigh two grams, about the same as a couple regular paper clips. A carat can also be divided into 100 ‘points’. Using points, one would refer to a half-carat diamond as a ‘fifty pointer’. A diamond of 0.25 carat weight would be called a ‘twenty-five pointer’. Obviously, as carat weight goes up, so does value.

There are many factors that figure in to the value of anything, diamonds included. Everything from local market conditions, strength of various currencies, supply, demand, etc, can affect the price of a diamond. But the 4Cs are the primary determinants of a stone’s intrinsic value. When you see a good stone, a really good stone, there will likely be a grading report from the GIA. On that report will be listed the values of the 4Cs. There are other grading organizations, but the GIA is the accepted standard around the world.

So when you go to buy your next diamond, whether it be for your sweetheart or for yourself, keep these qualities in mind. Cut, clarity, color, and carat weight will determine the value of that diamond. And, if you want it to keep some of that value (beyond the retailer’s mark-up!), make sure it is graded by the GIA. Their grading is accepted the world over.