Since most precious stones are rare and highly desirable, their market values are determined by a set of evaluation criteria known as the 4C – Carat, Clarity, Color and Cut. This system is used mainly to rigorously grade and determine the pricing of diamonds on the international market, but can also be applied to the grading values of other colored gemstones.
The unit weight measure of gemstones is carat ; 1 carat is equivalent to 0.2 grams in the metric scale, and can be further divided into 100 points. Therefore, the calculations of carats are usually carried to 2 decimal places by most major gemstone appraisal organizations, such as 0.30 carat or 1.52 carat. Generally, the larger the original gemstone crystal, the more rare it is. The same is true for finished gemstone products; the larger the carat, the more valuable the jewel is. It should be noted that carat is not always proportionate to pricing. For example, 1 carat of a gemstone may cost 30,000, but another identical gemstone at 2 carat may be worth at least 60,000 and above, more than double the value of the same stone at 1 carat.
Aside from transparent diamonds, the most important factor determining the value of a gemstone is its color . Generally, a valuable, high quality gemstone will possess color quality that is both pure and brilliant. For example, Pigeon Red rubies have the most valuable red color of all rubies, far more than deep red or purplish red rubies. Cornflower Blue sapphires are worth far more than sapphires of any other colors.
Clarity refers to the “ cleanness ” of gemstones, which is dependent on the amount of internal impurities and inclusions. Generally, gemstones with fewer impurities are more valuable. Gemstones usually acquire inclusions – materials trapped inside the crystallizing minerals- during their formation processes. These inclusions are important indicators of grading and authentication of gemstones. For examples, the silk like inclusions in rubies are important indicators of indentifying naturally produced rubies.
Cut is the only manually involved process during the production of gemstones. However, it is also what determines the value of the final end product. An excellent cutting style will bring out the brilliance of gemstones, emphasize their luster, accentuate their colors and bring out the uniqueness of each gemstone, thereby increasing their values.