How To Understand Gem Grading

Purchasing and owning of gem stones can be intimidating to the average consumer. In order to help out the consumer, gems are graded based upon their features using the "four C's." These grades rate the gems based upon the rarity of their features, not necessarily the quality. It is important to note that these grades are designed to identify the characteristics of the stones and quality is still based upon preference of the buyer.

Rarity is often what will drive the value of a gem, as the more "unique" the stone, the higher the premium will be. However, rarity is not the be all, end all of gem value. Even with rarity being a factor, a highly desirable stone may still have a high value, regardless of the rarity of characteristics. A good example would be diamonds and engagement rings; a trendy or popular cut may not necessarily be rare, but will still demand a cost premium due to the demand for that particular stone.
The four graded areas are color, clarity, cut and carat.

  1. Color is further broken down into three subcategories that further define the color.

  • Hue - What is the "simple" color of the gem (green, blue, red, orange, etc.)?
  • Saturation - How deep is the color? Is it deep or a light pastel?
  • Tone - Is the color light or dark within that particular color's range (dark blue vs. light blue)?

Regarding the effect of color on the value of a stone, it is really only critical in rare or high value gems. An emerald with a perfect green color will be worth more than one that is slightly faded or with a shade of blue. On a moderate or lower valued gem, the color is more of a matter of personal preference.

  • Clarity is the evaluation tool to determine the number of inclusions within the stone. An inclusion is anything in the gem that prevents the clean passage of light through the stone. Some inclusions may be visible to the naked eye, but having a gem without inclusions that you cannot see does not mean that it is free of inclusions. In fact, finding a stone with no inclusions is very rare. Most gemologists will view a stone with a 10x magnifier to determine if there are any inclusions. While not having any visible inclusions is usually preferable, it is important to watch for cracks and chips within the stone that may impact its durability.
  • Cut, the third "C," is the final product and appearance of the stone after it is shaped and cut. A higher grade will be given to cut based upon the appearance of the stone, including how vibrant is it and how well the cut reflects light. For most consumers, cut is a matter of preference and is commonly discussed in engagement rings.
  • Carat is the last grading criteria used on gemstones. Simply put, carat is the size of the stone. From a value perspective, larger gems are going to be worth more than a smaller stone if it has the same cut, clarity and color. Many jewelers determine the price of a stone on a cost per carat basis.
    While you now have a basic understanding of the four C's that are used in gem grading, the final factor is how satisfied you are with your gemstone. Remember, personal preference is what determines quality; the grading and evaluation simply determines rarity.


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