A gemstone is a piece of mineral which is cut and polished to make jewelry or other accessories. However, certain rocks like lapis lazuli and organic materials like amber and jet that are not minerals are often considered to be gemstones and make exquisite pieces of jewelry. Most gemstones are extremely hard with a rigid crystalline structure. But some soft minerals are also used in jewelry for their luster or other unique qualities that make them valued and valuable. The chemical composition of the gem determines most of its other properties like shape, strength, hardness and color. It may all sound quite arbitrary, but that doesn’t take the shine off from a wonderful piece of jewelry with a beautiful gem as the focal point.
The jewelry industry recognizes the highest quality gemstones by purity of their hue, the depth of tone, and the color saturation. The best value is in colors that include “slight” traces of other colors, are not too light or dark, and have a lot of saturated color. Nearly all gemstones today, including our stones, have been treated to enhance their color. The most common methods of treatment are heating, nearly always seen with aquamarine, citrine, amethyst, sapphire, ruby and tanzanite, bleaching commonly seen with pearls, and irradiation performed on nearly all blue topaz.
The beautiful color of a gemstone is its most defining characteristic, and many jewelers consider it to be the most important evaluation criterion. When deciding upon gemstone color, examine hue, tone, and saturation.
The most valuable gemstones are those that exhibit a pure color and only “slight” hues of other colors in addition to their primary color, as all gemstones do. For example, Bradley T. Harris Jeweler’s sapphires range in hue from “slightly purplish-blue” to “slightly greenish-blue,” pink sapphires always range from “pink” to “slightly purplish-pink,” and rubies range from “slightly orangish-red” to “slightly purplish-red”. With the exception of opals, variation in a gemstone’s hue will be called out in the gemstone details on the product detail page.
Tone represents the depth of color, ranging from colorless to black. Gemstone tone is described as “light,” “medium-light,” “medium,” “medium-dark,” and “dark.” For all of our gemstone jewelry, you’ll find any tone variations are called out in the gemstone details.
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 “vivid” or “strong” color saturation. Generally, the levels of color saturation will not be called out in the product details because the gemstones in our jewelry are hand-selected for their vivid colors.
Almost all gemstones contain inclusions. Even those most highly prized have at least some inclusions. Flawless gemstones are very rare and very expensive. The best value is found in gems that are lightly to moderately included. Emeralds are typically treated with colorless oil, wax or resin to minimize surface-reaching inclusions.
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 will not necessarily detract from the beauty or desirability of a colored gemstone.
What to Look For
When considering a colored gemstone’s clarity, you should measure your expectations against the standard for that variety of gemstone. Some varieties of colored gemstones, such as aquamarine, blue topaz, and citrine, have naturally fewer inclusions while other gemstones, such as emerald and ruby, tend to have a higher rate of acceptable inclusions.
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.
Unlike diamonds, with gemstones there isn’t an “ideal” cut geometrically configured for maximum brilliance. But a high-quality gemstone cut is one that presents the most even color, exposes the fewest inclusions, and displays the majority of the gemstone weight when set in jewelry. Colored gemstones are generally cut to maximize the beauty of their color. To recognize quality in the cut of a gemstone, there are several points to consider.
What to Look For
A good cut showcases the gemstone’s color, diminishes its inclusions, and exhibits good overall symmetry and proportion. Because gemstone color can vary, there are no hard geometrical standards when it comes to maximizing brilliance or color. Gemstones, especially rarer ones, are sometimes cut for size without regard for their color. For example, when corundum varieties such as sapphire and ruby are cut for maximum weight rather than beauty, they may display banded colors or streaks.
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 is not necessarily an accurate gauge for gemstone size. To help you judge the size of a gemstone, we list the diameter of the gemstone when viewed from above – since if the gemstone is set in jewelry; this is the only part of the gemstone that is visible.
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.
Gemstone Enhancement Processes
There are many methods of enhancing colored gemstones. We describe the most common enhancements below. For more information on colored gemstone enhancements, see the American Gem Trade Association’s Gemstone Information Manual.
- Heat Treatment
The application of heat to enhance the color and/or clarity of gemstones has been a common practice around the globe for centuries. It is part of the standard polishing and finishing process for many colored gemstones. As such, it is accepted by the jewelry industry and the American Gem Trade Association. The enhanced color and/or clarity of heat-treated gemstones is permanent.
The filling of a gem material with an oil, wax, glass, resin or other material, colored or colorless, to improve appearance. This process began centuries ago by gemstone merchants who found that immersing emeralds in oil or waxes made them look clearer to the unaided eye. This practice continues today with many colored gemstones.
The use of wax, resin or oil applied to the exterior of a porous colored gemstone to protect the natural substance, and to improve sturdiness and appearance.
The application of chemicals or other elements to lighten or enhance color consistency.
The act of adding coloring agents so that they permeate a colored gemstone to enhance or alter color.
The alteration of a gemstone’s color through the use of radiation. This is often followed by a heating process. The enhanced color of irradiated gemstones is permanent.
- New and Future Technologies
Techniques for enhancing colored gemstones, either detectable or otherwise, are continually being developed. These may be difficult, or in rare cases, impossible to detect, even for the most sophisticated laboratory.
While gemstones are durable, they require varying levels of care. For example, some gemstones are especially vulnerable to household chemicals and temperature changes. Cleaning gemstones presents special challenges. While many gemstones should be cared for by following our basic care guidelines below, please refer to our Gemstone and Pearl Care and Enhancement Overview to understand the care requirements for your specific stone. If you still have questions, please contact us.
After removing your gemstone jewelry, clean it by following the directions on a non-abrasive jewelry cleaner. Make sure that the jewelry cleaner specifies that it is safe to use with your gemstone. Use a soft cloth to remove any remaining dirt or other residue.
Store your gemstone jewelry in a lined case or a soft cloth, so the gems do not touch each other or parts of other jewelry. Gemstones are harder than gold, silver, or platinum and can scratch the surfaces of your other fine jewelry if they are not kept separate.
While it’s true that gemstones such as ruby and sapphire are second only to diamond on the hardness scale, it is not a measurement of their indestructibility. It means that these gemstones are able to resist scratching almost as well as a diamond. Abrasive surfaces, harsh chemicals, and sharp blows can damage even the hardest gem. Your gemstone jewelry should be the last thing you put on when getting dressed and the first thing you take off at the end of the night. Store your gemstones carefully and they will be enjoyed for generations.
|Gemstone||Accepted Enhancements||Gemstone Care|
|Amethyst||Heated to alter color.||Basic Gemstone Care.|
|Aquamarine||Heated to alter color and clarity.||Basic Gemstone Care.|
|Black Onyx||Dyed.||Basic Gemstone Care.|
|Blue Topaz||Heated and/or irradiated to alter color.||Basic Gemstone Care.|
|Citrine||Heated to alter color.||Basic Gemstone Care.|
|Diamond||None.||Basic Gemstone Care.|
|Emerald||Infused to alter clarity and/or color.||Do not use ultrasonic cleaning. Avoid sudden temperature changes, chemicals, perfume, cosmetics, and hairspray.|
|Garnet||None.||Avoid sudden temperature changes.|
|Opal||Coated to alter surface consistency and durability.||Do not use ultrasonic cleaning. Avoid sudden temperature changes, chemicals, perfume, cosmetics, and hairspray.|
|Pearl (natural and cultured)||Bleached, dyed, polished and coated.||Do not use ultrasonic cleaning. Avoid sudden temperature changes, chemicals, perfume, cosmetics, and hairspray.|
|Peridot||None.||Basic Gemstone Care.|
|Pink Tourmaline||Irradiated to alter color.||Do not use ultrasonic cleaning and sudden temperature changes.|
|Rose Quartz||None.||Do not use ultrasonic cleaning.|
|Ruby||Heated to alter color and clarity. Infused to alter color and clarity.||Avoid household chemicals and ultrasonic cleaning.|
|Sapphire||Heated to alter color and clarity. Infused to alter color and clarity.||Avoid household chemicals and ultrasonic cleaning.|
|Tanzanite||Heated to alter color and clarity. Infused to alter color and clarity.||Do not use ultrasonic cleaning and sudden temperature changes.|
|White Agate||Dyed.||Basic Gemstone Care.|