This guide defines the five essential characteristics of gemstone quality. By understanding these characteristics, you'll be able to shop with confidence.
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. Huang and Co. offers some of the highest-quality colored gemstones available. Nearly all gemstones today, 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.
- 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, as all Blue Nile gemstones do. For example, Blue Nile 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 - Tone represents the depth of color, ranging from colorless to black. Gemstone tone is described as "light," "medium-light," "medium," "medium-dark," and "dark." Blue Nile offers gemstones with the most sought-after tones that fall within the medium-light to medium-dark range. For all of our gemstone jewelry, you'll find any tone variations are called out in the gemstone details.
- 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 "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.
- 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.
- 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.
- Gemstone cut - 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, Blue Nile lists 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.
- Gemstone cut - 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.
Nearly all gemstones on the market, including gemstones offered by Huang and Co., have been treated to enhance their appearance. Gemstones that have not been treated but exhibit desirable color and clarity command extravagant prices. Some enhancement treatments are almost universal, are permanent, and require no special care of the gemstone, such as heat treatment to enhance color. Other treatments are common, and may require more or less special care to avoid damage, such as infusion of colorless oil, wax or resin to improve clarity.
- 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.
- Infusion - 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.
- Coating - 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.
- Bleaching - The application of chemicals or other elements to lighten or enhance color consistency.
- Dyeing - The act of adding coloring agents so that they permeate a colored gemstone to enhance or alter color.
- Irradiation - 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.