Throughout history, gemstones have been prized by royalty and worn as charms for protection and good fortune.
Precious gemstones are prized for their beauty and rarity. Because they are more rare than other gemstones, they are also considered more valuable. Diamonds, rubies, sapphires and emeralds are all considered precious stones.
Semi-precious gemstones are prized for their beauty, but they are less rare than precious stones. Topaz, citrine, amethyst, garnet and quartz are all considered to be semi-precious gemstones.
The beautiful color of a gemstone is its most defining characteristic. When deciding upon gemstone color, examine hue, tone, and saturation.
Hue: The most valuable gemstones are those that exhibit a pure color and only “slight” hues of other colors in addition to their primary color. For example, sapphires range in hue from “slightly purplish-blue” to “slightly greenish-blue” and rubies range from “slightly orangish-red” to “slightly purplish-red.”
Tone: Tone represents the depth of color, ranging from colorless to black. Gemstone tone is described as “light,” “medium-light,” “medium,” “medium-dark,” and “dark.”
Saturation: Saturation, or color purity, refers to the degree to which the gem is free from brown or gray hues. The most desirable gemstones, which show little gray or brown, are often described as having “viorong” color saturation.
Because gemstones form under unique circumstances, each individual gemstone is comprised of a combination of trace minerals, which create a unique set of identifying marks or inclusions. Inclusions do not necessarily detract from the beauty or desirability of a colored gemstone.
Clarity is an important factor in comparing quality colored gemstones. Even opaque opals can have milky inclusions that will affect their iridescence and color play. In general, the best values are available in gemstones that are moderately included. Exceptional gemstones with few or no inclusions are available, but they can command extravagant prices.
Colored gemstones are generally cut to maximize the beauty of their color. Just as with a diamond, a good cut showcases the gemstone’s color, diminishes its inclusions, and exhibits good overall symmetry and proportion.
Look at the gemstone in the setting and ensure that all the facets are symmetrical. An asymmetrically-cut crown indicates a gemstone of low-quality. In all cases, a well-cut gemstone is symmetrical and reflects light evenly across the surface, and the polish is smooth, without any nicks or scratches.
The carat weight of a gemstone does not necessarily allow you to accurately envision the size of the gemstone. Different gemstones have different densities (mass per unit volume), so two gems that appear to be the same size may actually have very different weights. For example, a ruby is more “dense” than a diamond, so a 1-carat ruby will look smaller than a 1-carat diamond.
Due to their rarity and unique visual properties, gemstones commonly undergo a number of techniques to enhance their color, clarity and/or durability. Colored gemstones that have not been enhanced are very rare and command extravagant prices.
The use of heat to enhance the color of gemstones has been a common practice around the globe for centuries. It is part of the standard polishing and finishing process for many gemstones including aquamarine, citrine, amethyst, sapphire, ruby and tanzanite. As such, it is accepted by the jewelry industry and the American Gem Trade Association. The enhanced color of heat-treated or irradiated gemstones is permanent and does not require special care or disclosure.
Infusion is the filling of a gem material with a colored or colorless oil, wax, glass, resin or other material to improve appearance. This process began centuries ago by gemstone merchants who found that immersing emeralds in clear oil or waxes made them look clearer to the unaided eye. This practice continues today with most colored gemstones.
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