The five essential characteristics of gemstone quality.
There are five essential characteristics of gemstone quality. These characteristics, combined with rarity, durability, and beauty, determine the value of all gemstones. A better understanding of these technical aspects will greatly assist you in making the best choice when shopping for the best value in gemstone jewelry.
Color is the most important factor affecting the value in colored gems. Those with full saturated color and medium tones will generally appear the most beautiful and most expensive. The best value will be in gems that are not too light or dark in tone and well saturated in color. Earth Treasures’ gemologists are experts in selecting the very best values.
Hue is the precise spectral color of a gem. Specific gemstones are usually found in a range of hues. The primary hue is the main color accompanied by secondary hues. For example, rubies range in hue from slightly purplish-red to slightly orangish-red. At Earth Treasures, we try to stock only those gemstones with desirable hues.
Tone refers to the depth of color from light to dark. Dark tones in rubies and sapphires are not desirable because the gems lose their transparency and appear inky. Light tones in any gem will give them a washed-out appearance. We strive for medium to medium-dark tones for optimal beauty.
This refers to the purity of color which is affected by overtones of brown and gray. Overtones will make a gemstone look less vivid or intense; therefore, strong color saturation is the most desirable.
Evenness of color can drastically affect the beauty of gems. In some stones, color isn’t evenly distributed but may exist in zones. This is frequently observed in sapphire, ruby, amethyst, and citrine. When a gemstone is tilted or rotated, streaks of colorless or lighter tones may be observed. Obvious color-zoning is not desirable and should be avoided.
Colored gemstones are drastically affected by surrounding colors in a room or lighting conditions. Be aware that gems will often appear different under different conditions. Rubies look best in natural daylight or incandescent light bulbs and worst under cool white fluorescent lights. This is due to the lack or presence of some spectrum colors in various light products. For this reason, rubies appear richer in yellow gold and sapphires look better in white gold.
Clarity refers to the absence of internal flaws called inclusions. Almost all gemstones contain some array of inclusions, even the most high-end specimens. The best value is found in gems that are lightly to moderately included. At Earth Treasures, we avoid heavily flawed commercial qualities.
Variance of severity among different gemstones
Due to the fact that each species of gemstones is formed under different conditions and extremes, some species, such as emerald, are typically found very heavily included, while others, like amethyst, are more commonly found near flawless. Therefore, one could rightly expect that a large premium in price would be expected for a near flawless emerald, but very little additional for the same clarity amethyst.
What you should look for
In general, if the inclusions weaken the stone’s durability, affect color, are easily noticeable, or are too numerous, they will significantly reduce price and value. The gemstone should look lively and pleasing to the eye. Remember that emeralds are by nature heavily included so expect to pay considerably more for less included ones. To a lesser extent, the same holds true for rubies while sapphires generally are more readily available in higher clarities. At Earth Treasures, our trained Gemologists avoid buying stones with problem inclusions and indicate clarities for all major gems we sell.
Although color is the most important criteria for determining the value of a gemstone, cut will materially affect how color is rendered to the eye. It affects the depth of color seen in the stone and influences the liveliness projected by the stone. If a gemstone is poorly cut, it will have a flat look or “windowed” appearance. This failure to cut close to critical angles causes unsightly reflections of the underside of its mounting or the wearer’s finger. A gemstone that is well cut will give off brilliance and sparkle from all angles.
What you should look for
Frequently, sapphires and rubies are cut excessively shallow or deep to utilize as much of the rough as possible. Very dark material can be salvaged by cutting very shallow bottoms (pavilions) to maximize light absorption and transparency. Very light colored material can be cut very deep intensifying color and allowing additional weight retention.
Avoid gems that look lifeless or lumpy in their setting. When selecting mountings with very small stones, see if “diamond cut” or “machine cut” material is available. Due to their superior cutting, these little gems will show maximum sparkle. At Earth Treasures, we avoid “native” or inferior cuts whenever possible and specialize in colored gems cut to exacting proportions.
It is important to remember not to confuse size with carat weight. From everyday life, you realize that different materials have different densities. A cast iron skillet is much denser or heavier than an aluminum skillet of the same size. The same holds true for gemstone species. As a general reference, sapphire and ruby are 1.2 times as heavy as diamond so a 1-carat ruby will appear smaller than a 1-carat diamond. While tourmaline is 1.2 times lighter than diamond, it will appear larger for its weight.
In addition, colored gems are cut differently from diamonds with different critical angles so size versus weight varies considerably. The bellies or pavilions of colored gems are generally cut with a greater bulge making them heavier.
For these reasons, we provide length and width dimensions as well as carat weight for all our primary gemstones.
The transition from the mine to the final polish is laborious and challenging. The majority of gemstone rough is not suitable for faceting and fashioning into exquisite jewelry. The miners and cutters must work together to utilize as much material as possible. Hundreds of years ago, techniques such as heating of rubies and sapphires, oiling of emeralds, and bleaching of pearls were developed to improve their appearance. Such practices are not harmful and are considered acceptable by the gemstone industry.
However, there are many unethical enhancements that exist in the marketplace and you should only deal with gemologically trained jewelers who can distinguish natural from altered gems. Glass filled, diffusion, and synthetics are readily offered undisclosed on the internet to the unsuspecting.