|A gemstone or gem, also called a precious or semi-precious stone, is a piece of attractive mineral, which — when cut and polished — is used to make jewelry or other adornments. However certain rocks, (such as lapis-lazuli) and organic materials (such as amber or jet) are not minerals, but are still used for jewelry, and are therefore often considered to be gemstones as well. Most gemstones are hard, but some soft minerals are used in jewelry because of their lustre or other physical properties that have aesthetic value. Rarity is another characteristic that lend value to a gemstone jewelry .
Characteristics and classification
Gemstones are identified by gemologists, who describe gems and their characteristics using technical terminology specific to the field of gemology. The first characteristic a gemologist uses to identify a gemstone is its chemical composition. For example, diamonds are made of carbon (C) and rubies of aluminium oxide (Al2O3). Next, many gems are crystals which are classified by their crystal system such as cubic or trigonal or monoclinic. Another term used is habit, the form the gem is usually found in. For example diamonds, which have a cubic crystal system, are often found as octahedrons.
Gemstones are classified into different groups, species, and varieties. For example, ruby is the red variety of the species corundum, while any other color of corundum is considered sapphire. Emerald (green), aquamarine (blue), bixbite (red), goshenite (colorless), heliodor (yellow), and morganite (pink) are all varieties of the mineral species bery.
Gems are characterized in terms of refractive index, dispersion, specific gravity, hardness, cleavage, fracture, and lustre. They may exhibit pleochroism or double refraction. They may have luminescence and a distinctive absorption spectrum.
Material or flaws within a stone may be present as inclusions.
Common treatments applied to gemstones
*Heating can lighten, darken or change the color of some gems, or improve a gemstone clarity.
*Irradiation can add more color to colored diamonds, certain other gemstones and pearls.
*Impregnating some gems with colorless oils, wax or resins makes a variety of imperfections less visible and can improve the gemstones' clarity and appearance.
*Fracture filling hides cracks or fractures in gems by injecting colorless plastic or glass into the cracks and improves the gemstones' appearance and durability.
*Diffusion treatment adds color to the surface of colorless gems; the center of the stone remains colorless.
* Dyeing adds color and improves color uniformity in some gemstones and pearls.
* Bleaching lightens and whitens dome gems, Including jade and pearls.
The Rainbow of Gemstones
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 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 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, 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.
Synthetic and artificial gemstones
Some gemstones are manufactured to imitate other gemstones. For example, cubic zirconia is a synthetic diamond simulant composed of zirconium oxide. Moissanite is another example. The imitations copy the look and color of the real stone but possess neither their chemical nor physical characteristics.
However, lab created gemstones are not imitations. For example, diamonds, ruby, sapphires and emeralds have been manufactured in labs to possess identical chemical and physical characteristics to the naturally occurring variety. Synthetic (lab created) corundums, including ruby and sapphire, are very common and they cost only a fraction of the natural stones. Smaller synthetic diamonds have been manufactured in large quantities as industrial abrasives. Larger synthetic diamonds of gemstone quality, especially of the colored variety, are also manufactured.
Whether a gemstone is a natural stone or a lab-created (synthetic) stone, the characteristics of each are the same. Lab-created stones tend to have a more vivid color to them, as impurities are not present in a lab, so therefore do not affect the clarity or color of the stone. However, natural gemstones are still considered more valuable on average due to their relative scarcity.
Basic Gemstone Care
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 Blue Nile customer service.
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.