Mark Peter's Diamond Designs

What You Need To Know About Diamonds

There are four characteristics
that determine the value of any diamond:
cut, color, clarity, and carat weight.


Cut refers to how a diamond has been shaped by a diamond cutter to best bring out its fire. Regardless of the gem's overall shape (round, emerald, pear, etc.), a diamond with a high-quality cut will more effectively manipulate light and appear more brilliant. A highly-skilled diamond jeweler will maximize a diamond's luster through careful cutting and polishing. For this reason, cut is perhaps the most important of the four C's, and the clearest indication of the cutter's skill.


Because of how they are formed, colorless diamonds are exceptionally rare. Nearly all diamonds have some color in them, usually some amount of yellow or brown. With the exception of unique colors, diamonds are graded on color from D (very little color) to Z (the most color, most often shades of brown). The less color a diamond has, the more brilliant it will be, and the greater its value.


Clarity is the evaluation of a diamond's internal and external characteristics. The fewer inclusions or blemishes, the more desirable the diamond. Inclusions are visible defects inside the diamond, such as the presence of crystals (minerals trapped inside the diamond) and feathers (breaks in the diamond). Blemishes are usually very small and are only on the surface of diamonds. To locate these tiny characteristics, a grader will use a binocular microscope that magnifies the diamond ten times. Then, evaluating the size, location, nature, number, and color of all the inclusions and blemishes, a clarity grade from Flawless to Included will be given:

  • F – Flawless

    No internal or external flaws. Extremely rare.

  • IF – Internally Flawless

    no internal flaws, but some surface flaws. Very rare.

  • VVS1-VVS2 – Very Very Slightly Included (two grades).

    Minute inclusions very difficult to detect under 10x magnification by a trained gemologist.

  • VS1-VS2 – Very Slightly Included (two grades).

    Minute inclusions seen only with difficulty under 10x magnification.

  • SI1-SI2 – Slightly Included (two grades).

    Minute inclusions more easily detected under 10x magnification.

  • I1-I2-I3 – Included (three grades).

    Inclusions visible under 10x magnification as well as to the human eye. We do not recommend buying diamonds in any of these grades.


Carat is the standard used to measure diamond weight. A carat equals 1/5 of a gram (or 1/142 of an ounce). Each carat is divided into points, each point representing 1/100th of a carat. While weight may be the least important of the four Cs in determining value, it is the easiest to gauge accurately. As diamonds increase in size, their cost tends to increase geometrically. A one-carat diamond may cost more than twice as much as a one-half carat stone of equal quality. Also, as previously stated, weight doesn't always enhance the value of a diamond. In fact, when a diamond is improperly cut, added weight may serve only to reduce its brilliance.

The Fallacy of Certified Diamonds

Many jewelers purport to have their diamonds "certified" by independent labs. In reality, NO lab certifies diamonds. They issue a very professional-looking "certificate" with their opinion of clarity and color. If you read the disclaimer found on the back of nearly any lab's report, it states this is their opinion of the diamond, and is not a guarantee of the clarity and color.

The quality of lab reports varies widely, even within the same lab. A diamond graded G color SI1 clarity may be graded an F/ VS1 by a different lab, and H/SI2 by a third lab. Even submitting the same diamond to the same lab can result in a different grade on each report. Grading is very subjective, and not all labs are "created equal". On a 1ct diamond with the grading spread listed in this example the dollar differences could be in the thousands.

At Mark Peter's, we strongly recommend that you not base a diamond purchase solely on a grading report, regardless of the issuing lab.

We regularly see diamond certificates by labs we consider reputable that we know are inaccurate at best. We do not present marginally graded diamonds to our customers. We sell quality diamonds, not lab reports, at affordable prices.