Determinig the Value of a Gem

The article gives the information regading the methods of determining the quality of gems and semi-precious stones.

There are several systems to determine the quality of gemstones in the world. Some of these systems are more known and popular than others. Almost all of them are identical in respect of measurement parameters, but with different scales of measurement. There is no one universal system of gemstones’ assessment. Therefore, even in one country several systems can peacefully exist.

The most popular system in the United States and probably anywhere abroad is 4C system, developed by the Gemological Institute of America. 4 C - is the 4 main parameters on which stones are assessed: the color, clarity, cut and carat (weight). To these a fifth C, Color Coverage, can also be added .This system has three versions: for diamonds, colored stones and pearls, meaning it can be used to determine almost any jewelry.

What is the brief principle of this system?

The color of Diamonds has 23 grades starting from D (colorless) to Z (light yellow). The color D is the most valuable. Gray and brown colors are evaluated on the same scale. More intense colors and other colors known as "fantasy" and evaluated differently. Such stones are rarely encountered.

There are two key factors in judging Diamonds clarity: impact on durability and visibility of inclusions.All diamonds are divided into 11 clarity groups (in descending order): FL, IF, VVS1, VVS2, VS1, VS2, SI1, SI2, I1, I2 and I3.

Evaluation of cut involves five major features: cutting style, proportions, shape, symmetry, finish. Diamonds are divided into 4 classes (upper class 1) on the quality of cut. In price-lists a price is usually set for Class 2. For other classes increasing or lowering rates are used.

Weight in gems is calculated in metric carats - one carat is equal to 0.2 grams, about the same weight as a paperclip. There is another term “karat” in jewelry used to define gold purity. It is important to understand that it is two completely different terms. In the diamond industry, weight is often measured to the hundred thousandths of a carat, and rounded to a hundredth of a carat. 

To evaluate colors of other gems (except of Diamonds), a special scale of color exists. It allows to select 324 color options. By clarity all gems are divided into 7 groups (in descending order): VVS, VS, SI1, SI2, I1, I2 and I3. In addition, gems are divided into three types. Topaz, for example, refers to the type 1 and Emerald to the type 3. The quality of cut requirements for other gems are somewhat lower than the quality of Diamonds’ cut.

The main role in determining the gem is a color. In price lists 50 percent of the stone’s value is determined by the color. Some dealers can raise this ante to 70 percent. The clarity of stones takes 20-30 percent of the cost and the quality of cut - only 10-20 percent.

Pearls are classified by color and flow, shape, luster, size, thickness of the pearl layer, clarity and uniformity of selection (in the thread). In addition, Pearl is divided into natural and cultured, marine and freshwater, post production and some other parameters.

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