Diamond Buying Guide

Jewelry Buying Guide

Outside of a home or car, the purchase of a diamond can be one of the largest expenditures a person ever makes. Also, because the emotional events most often associated with a diamond and by the simple fact that we simply don’t buy them often, this purchase can seem intimidating. It doesn’t have to be this way! With a little education about how diamonds are graded, you can feel a lot more comfortable in making a selection that is proper for you and the person for which the diamond is intended. This Primer on diamonds covers the basics you will need to know to start you on the path to finding the right diamond along with a few hints that might help you save a little bit of money too.

You may have heard of the 4 C’s of diamonds, but let’s throw in another C and add an S to round out what you need to know about these incredible stones. For the uninitiated, the traditional 4 C’s are Cut, Clarity, Color, and Carat. For the purpose of this article, we’ll also add in Certification and Shape (which is different than Cut). These areas are the most important and relevant things to consider when determining the quality of a diamond. As long as you have a good, basic understanding of these areas, you are much more prepared to make a truly informed buying decision. Let’s delve into each of these areas.


Although, not listed first in our list, let's start with Carat. You probably already have an idea of what carat means. The carat is actually a unit of weight which is equal to 200 milligrams. This unit was created in the early 1900’s and has been in use ever since. Just so you have a practical idea of weight, a carat is about equivalent in weight to a standard paperclip. Just like a dollar is divided into 100 pennies, a carat is divided in to 100 “points”. Therefore a 75 point diamond weight 0.75 carats. One quick word of caution—carat weight by itself is not an accurate measurement of a diamonds size. You must also consider the width (measured in millimeters) and the type of cut. Different cut styles and shapes determine the apparent size of the diamond.


Diamond prices usually jump at full and half carat weights. To get the best value, search out diamonds that are just below these weights. For example, you might want to get a 1.45 carat diamond as opposed to a 1.5 carat. You won’t be able to tell by the naked eye a size difference, but the savings can really be significant!


Next, let’s take the first “C”, cut. Not to be confused with “Shape”, a diamond's cut is a measure of how cutting the diamond affects the diamond’s light performance. In other words, if the diamond is cut with correct proportions, it will reflect more light back to the eye through the top of the diamond (called the “table”), creating more sparkle. If the diamond’s cut is too shallow, light leaks out of the bottom and if the cut is too deep light escapes from the sides. While diamonds come in many different shapes, cut has to do with proportion and the arrangement of facets. The final beauty of a diamond depends more on cut more than anything else.

Newly mined diamonds are in the “rough”. It’s up to a skilled diamond cutter called a diamantaire to study, properly cut, and polish the diamond. If the diamantaire makes even the smallest mistake, the diamond could be ruined! It could shatter, or be improperly proportioned. Regardless of the mistake, the diamonds value could be ruined. Once the diamantaire determines how best to proceed, the stone is carefully cut, polished, and proportioned to achieve the highest grade possible. The overall cut grade is follows a scale from Excellent to Poor. The grade depends on the proportions, angles, polish and symmetry of the facets. If any one feature is not proper, the grade, and therefore the value of the stone are affected. An excellent cut grade is preferred as it maximizes the diamond's light performance. Following are some examples of cut grades. Remember that different retailers may have slightly different standards for grading.

Excellent or Ideal cut: These stones represents only about the top 3% of diamonds. They reflect nearly all of the light that enters the diamond.

Very good cut: These diamonds are about the upper 15% of all stones. They have almost as much sparkle as an ideal cut, but very often have a lot lower price.

Good cut: Representing the top quarter of all stones, these diamonds are still beautiful, but are priced significantly lower than the very good cut. There is a visible difference between the good cut and the ideal cut.

Fair cut: Fair cut stones are in the top 35-40% of stones. These are still quality diamonds, but they will not be as brilliantly reflective as the higher grades.

Poor cut: These diamonds are generally cut too deep and narrow or shallow and wide and they lose most of the light out the sides and bottom.


Now we have our next C — color. This is the actual color of the stone and not the reflected light, which is caused by the prismatic sparkling of the diamond. Diamond color usually ranges from colorless (or white) to yellowish brown and is based upon trace elements absorbed into the diamond’s carbon matrix when it was being formed. The color scale is pretty simple to follow and it ranges in alphabetical order from D, which is colorless, to Z which is distinctly yellow-brown. In general, most people are shopping for as near colorless as possible. Colorless diamonds are extremely rare and very valuable. Most stones will have some coloration, most of which is so subtle as to be invisible except to a person with training. Still, these coloration differences greatly affect the value of the stone.

In contrast, there are fancy diamonds that do have color especially like pink and blue. These colorations are not considered a negative.


  • The human eye tends to detect sparkle or light performance, before color. Therefore, color is somewhat secondary to cut with respect to value.
  • Also, as the size of diamond increases, the color becomes more noticeable. This can be especially important if you are considering purchasing a stone of 2 carats or larger. The visible difference between concurrent color grades (ie, F and G) is almost unperceivable, but the difference in price can be significant.
  • Shapes of diamonds that naturally have more sparkle, like a brilliant round or princess cut, can mask some color in a diamond.
  • When choosing a setting, remember that the metal you choose can complement the color of the stone you are setting. For example, you may want to consider setting an E color stone (nearly colorless) in white gold or platinum to accentuate the lack of color in the stone.


Clarity is the next characteristic we’ll cover. The basic definition of clarity is the number and type of imperfections (called inclusions) in the stone as seen under 10x magnification. The flaws found inside the diamond may include trapped minerals from when the diamond formed or internal fractures due to the diamond's structure. The lower the amount of flaws, the easier it is for light to flow through and reflect off the diamond. This creates a greater sparkle. Clarity is rated on a scale from flawless (F) to inclusions visible (I), with additional grades indicating very very slight (VVS), very slight (VS), or simply slight inclusions (SI).

The amount of flaws in and on a diamond, as well as the color and location of the flaws affect its clarity grade. In most cases, you may not even see these inclusions with magnification let alone with your naked eye. It is a good idea to remember that in many cases, a single large flaw is worse than numerous small ones when it comes to clarity.


If you have a tight budget, you may be able to purchase diamond with a visible imperfection but have is set in a ring in such a way that a prong may hid the flaw. Also, as diamond size increases, the size of the facets also increase. A larger facet means that it is easier to see inside the diamond, making high clarity even more important.


Diamonds come in a pretty wide variety of shapes. The diamond cutter examines each stone to determine what shape would best accentuate the positives of that particular stone. Below are brief descriptions of each shape.

Round--The round brilliant cut diamond is by far the most popular and researched diamond shape available today. Diamond cutters have been researching and determining the precise mathematics of round diamonds for over 100 years. Besides being the most popular shape, a round diamond will typically give you the most flexibility in terms of balancing cut, color, and clarity grades while still getting the fire and brilliance you want.

Princess--The princess shape is the most popular non-round diamond. It’s natural brilliance and unique cut makes it a favorite for engagement rings. The princess has pointed corners and is traditionally square in shape, although they can vary in their dimensions to be slight rectangles. Emerald—The emerald cut is a rectangular shaped diamond. It has a large flat table (top facet) that can enhance the clarity of the stone. If you choose an emerald-cut with a lower clarity grade, such as SI, be sure to review the clarity plot on the diamond certificate. Emerald-cut diamonds can vary greatly in how rectangular they are. A square emerald cut is called and Asscher-cut diamond.

Marquise--The marquise shaped diamond is an oval with pointed ends. The shape of a marquise diamond can maximize carat weight, giving you a much larger-looking diamond. The length of the marquise shape can accentuate fingers making them look long and slender. The marquise also looks beautiful when paired with other shapes such as pears.

Oval--Oval diamonds have a natural brilliance that's similar to a round stone. Unlike round diamonds, they have two sides that are slightly longer and the ends are rounded, in comparison to the pointed end of the marquise shape. Like the marquise shape, ovals are also very popular in that you can use their length ratio to accentuate long, slender fingers.

Radiant--Radiant shaped diamonds are square to rectangular in shape and have corners that are slightly trimmed, providing more facet and slightly more sparkle. A radiant-shape looks beautiful set on its own or with baguettes or round side-diamonds.

Pear--This diamond shape is also called a teardrop and has a single point and rounded end. The unique look of the pear shape helps make it a popular choice for a variety of diamond jewelry. A pear shape that is slightly elongated can create a subtle slimming effect on the fingers.

Heart--The heart shape is pretty self explanatory. This shape has a single pointed end and a rounded end with an indention. It is the ultimate symbol of love. The unique look of the heart-shaped diamond helps make it a popular choice not only for rings, but especially for necklaces.

Cushion--Cushion-shaped (or pillow cut diamonds) are square or rectangles with curved corners. They are cut with larger facets to increase their brilliance. These larger facets highlight the diamond's clarity, so if you choose an SI clarity grade, be sure to review the clarity plot on the diamond certificate.


The final “C” we will discuss is certification. A diamond certificate, which can also be called a diamond grading report or diamond quality document, is a report created by a team of gemologists. As the term may suggest, a gemologist is a person who is trained to objectively study and grade stones. A completed certificate includes an analysis of the diamond’s dimensions, clarity, color, polish, symmetry, and other characteristics. Before purchasing a diamond, you should ask to review a copy of its certificate as proof that it has undergone an unbiased, professional examination. The Gemological Institute of America (GIA) Diamond Grading Reports are the most common reports that you will see. You may also see reports from other groups such as the American Gem Society (AGS) and American Gem Trade Association (AGTA).

Well, those are the basics of the 5 “C”s and 1 “S” of diamonds. As you can probably guess there is a lot more to each of these topics, but hopefully this primer will provide you with enough information to help you begin your search for the perfect stone for you. As a reminder, the better a diamond is in each of the Cs, the higher the price will be. As you begin the adventure for searching for your ideal diamond, think about which of the Cs are most important to you and those on which you can compromise on to help save a little money.