Since there is no standard grading system for gemstones it can be quite difficult to make a good purchase if you aren’t aware of the basic characteristics of the gemstone and what you should look for. The only global, standardized grading system in existence is for white diamonds, which was developed in the 1950s by the Gemological Institute of America.
There are certain factors that affect the value of a gemstone such as color, cut, size, clarity and any procedures that the gem has been subjected to so as to enhance its existing qualities.
- Color :-
Many experts in the field consider color to be the most important factor when determining the value of a gemstone. Depending on the gemstone, you can find a wide palette of colors for the same type of stone, whereas there are others that come in a much more limited array of colors.
When you consider the color of a gemstone you need to look at the hue, tone and saturation. Hue refers to the color itself which is made up of the different primary colors, namely blue, red and green. The more pure the hue of a gemstone the more valuable it is. For example, if a stone is referred to as being green, it will be more valuable than one that is considered bluish-green.
Tone refers to the lightness or darkness of the color, in other words the difference between pale blue and vivid blue. The lighter the tone, the less color the gemstone will have. Likewise, the darker the tone, the more color the stone will exhibit. The most valuable gemstones are those that range from medium-light to medium-dark.
Saturation represents the intensity of the color which translates into the amount of brown or gray found in the color of the gem. The more intense the color, in other words the lower the amount of brown or gray, the higher the value of the gemstone will be.
When buying gemstones personal preference is the most important factor in terms of color. If a certain color strikes your fancy then you shouldn’t hesitate to purchase whichever gemstone has the most personal appeal.
- Cut :-
Gemstones do not have an ideal cut because of the variety of colors and structures they exhibit. However, just like there are a wide range of colors to choose from, so too are there a wide range of cuts available for you to choose from.
The cut is extremely important to a gemstone as it is what reveals a stone’s beauty. The more artistic and creative the cut, the more impressive the gem will be which clearly relies on the skill, technique and patience of the cutter.
When judging the cut of a gemstone, you need to hold the gemstone out at arm’s length and rock it slightly. This will help you determine symmetry and judge the overall shape of the stone. A gemstone that has been well cut will present a good overall symmetry, exhibit few impurities and have good proportion.
Additionally, since the main goal of cutting the gemstone is to show off the color of the stone to its advantage, you should make sure the cut does its job. For example, a gemstone with a higher degree of saturation will look better if the cut is shallow as this allows more light to pass through and makes the color more brilliant. On the other hand, a gem with lower saturation will be shown off to perfection with a deeper cut.
- Size :-
Gemstones, just like diamonds, are weighed and priced by carat. One carat is the equivalent of 200 mg. However, not all gems are created equal in terms of density, which is why carats are not necessarily an accurate measure of size. For example, a sapphire is much denser, thus heavier, than an emerald and a 1 carat sapphire will be smaller than an emerald.
Simply because a stone is larger does not always make it more valuable. The rarity of the size also contributes to the value of the gem, so a gem that is most often found at 10 carats will be less valuable than a gem that is rarely found at that size.
Likewise, the per carat value of the same gemstone will be much higher in its rarer size than the same stone weighing in at a size that is readily available. For example, the price per carat of a 3 sapphire ruby will be much higher than a one sapphire ruby of the same quality.
Size versus price is also a good measure of the other qualities of a gemstone because if the price per carat is much higher for one size than another, then it is likely that there are also significant differences in color, clarity or cut.
- Clarity :-
Gemstones are pieces of mineral that grow in nature and each gem does so under different circumstances. This means that each gem will have different inclusions which are essentially tiny pieces of another mineral that develops or gets caught inside the gem as it grows.
Inclusions rarely detract from the beauty or desirability of a gem unless they are especially unsightly. More often than not, they enhance the beauty of the gem and can also be used as proof of the fact that the gemstone is natural and not synthetic.
There are different standards for different types of gems when it comes to clarity. For example, emeralds have a higher degree of inclusions that are considered acceptable compared to citrine, which naturally has fewer inclusions.
Of course, the fewer inclusions a gemstone has the higher its value will be. There are some extraordinary gemstones that are available with no inclusions whatsoever but these are extremely expensive.
For the best value for money you should look for gemstones with a moderate level of inclusions as they don’t detract from the beauty of the stone but will make the price slightly lower than a gem of the same size and quality with fewer inclusions.
- Enhancements :-
Any processes used to enhance the beauty of a gemstone other than cutting or polishing are known as enhancements. These are universally accepted procedures as they improve durability, appearance and even availability in some cases.
The main enhancement procedures are heat treatments, infusion, coating, bleaching, dyeing and irradiation. Gemstones are treated with heat to improve their clarity and color. It is a procedure that has been used all over the world for centuries and the result is permanent.
Infusion represents filling any cracks or fissures in a gemstone with oil, wax, glass, resin or other materials. They can be colored or not and are meant to improve the appearance and durability of the gem.
Coating involves the use of wax or oil to protect porous, colored gemstones. The latter absorb the wax or oil and become sturdier and their appearance is greatly improved.
Bleaching is the process by which chemicals are applied to lighten or enhance the color of a gemstone. When dyeing a gemstone, coloring agents are added to enhance or change its color. Irradiation is a process that has similar results, except that radiation is used to alter color. This color alteration is permanent.
