Gem Guide

When you are shopping for fine jewelry, not only do you want to find something that will fit the persons style, you also want to be sure you are getting the best value. When it comes to diamonds and other gemstones, understanding the 4Cs will put you on the right track.

The 4Cs are cut, color, clarity, and carat weight. The standards were established by The Gemological Institute of America (GIA) in the mid-1900s to help the public understand how diamonds are evaluated. The 4Cs became the globally accepted standard for describing diamonds and many other gemstones.

Diamond ring in gift box


Of all the 4Cs, cut has the greatest impact on a gemstone’s beauty. If the gemstone is cut poorly, it won’t refract light very well, even if it’s the highest color and clarity possible. The gemstone’s cut is maximized when the cutter carefully considers the best way to cut the stone that will make the most of its brilliant possibilities.

GIA’s diamond grading considers the proportions of the diamond and the accuracy of its overall symmetry and polish. They use the latest in technology to analyze the cut’s impact on the diamond’s light performance. The grading scale includes five levels: Excellent, Very Good, Good, Fair, and Poor. We suggest choosing cut grades of Excellent or Very Good.

Loose diamond in tweezers


Color is the next most important quality in a diamond. The GIA’s color-grading scale begins with the letter D for colorless diamonds, and continues with increasing presence of color to the letter Z. Diamonds come in various shades, most commonly yellows to browns, then they reach the fancy colors. GIA’s scale for “Fancy” colored diamonds is completely different. Contact us for more information. GIA uses the most recent lab equipment and technology which have met exacting standards to grade color. Remember a diamond that is graded loose, can only be assigned one color grade.

Other gemstone color evaluation includes three criteria: hue, tone, and saturation. Hue refers to the specific color of the stone. It’s best for a stone to have the purest hue possible, so any secondary color should be very minimal. Tone describes the level at which the color is seen in the stone. For instance, a gemstone can be green, but it can be a very light shade of green or display an extremely deep green color. The saturation of a stone is how strongly the stone’s color shows versus any possible gray or brown hues that may be present in the gem.

Diamond ring on platform


Sometimes you might hear someone compliment a friend’s diamond, and say “Your diamond is so clear and sparkly!” You might think that’s a diamond that is way up on the clarity scale, but you’d be wrong. That’s a diamond that is cut beautifully and is likely near colorless, or colorless.

Clarity is actually the evaluation of a gemstone’s internal and external characteristics. GIA grades clarity at 10 power magnification. Clarity is based on the size, location, nature, number, and color of the inclusions and blemishes. Then a grade of Flawless (the rarest) to Imp is given. A flawless diamond has no inclusions visible at 10 power. Some terms GIA gives to these natural characteristics occurring in diamonds are crystals, feathers, clouds, and needles.

Why should a diamond have independent lab report?

The Gemological Institute of America (GIA) provides independent lab reports for diamonds and other gemstones. A report from them will help you make an educated choice before you make a purchase or help you secure an accurate appraisal.  GIA has the highest standards when it comes to evaluating a diamond’s cut, color, clarity and carat weight.

GIA’s reports on colored gemstones utilize an extensive database and sophisticated analytical tools to identify synthetics, simulants and stones that have undergone treatment. Determining if a gemstone’s color is natural or the result of a treatment process is particularly important.

GIA is an independent organization who educates future gemologists, bench jewelers, appraisers and more. They are a disinterested third party because they do not buy diamonds or gems and they do not assign value. Learn more at


Carat is the standard measurement of a diamond or a gemstone’s weight. There are 100 points in 1.00 carat. The actual weight of a diamond can significantly impact the value. For example, if grades of cut, color, and clarity are the same, a 2.00 carat diamond will easily cost more than twice the price of a 1.00 carat.

Weight does not always enhance the value of a diamond or other gemstone. If a diamond is improperly cut, the added weight will reduce the brilliance. Some gemstones such as the ruby are often found in large sizes, but it is extremely difficult to find a ruby with high clarity, so a much smaller ruby with few inclusions will cost much more.

The shape of a diamond will also affect its price. Round diamonds have always been the most popular. Other shapes come in and go out of popularity, which can affect the price. What’s amazing about diamonds is that while two stones may weigh the same and receive the same grades from the GIA for cut, color and clarity, they are never identical internally.

Enlarged diamond

Preusser Jewelers Are Gemstone Experts

The experienced and knowledgeable staff at Preusser Jewelers can help you find a quality stone that will fit your budget. Our staff can tell also you all about the cut, color, clarity, and carat of a gemstone you are considering buying or give you an accurate appraisal of one you already own.

Our jewelry store is located in the center of the Bill and Pauls Sporthaus Plaza at 1200 East Paris SE #2.  We are open Tuesday through Thursday from 10am to 6pm, Friday from 10am to 7 pm, and Saturday from 10am to 4pm. We always welcome new and returning customers. Contact us today to learn more.

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