Gemstones and gems are often referred to as precious or semi-precious stones. These attractive minerals are transformed into much sought-after jewelry or other adornments through a process of cutting and polishing. Other rocks, such as lapis-lazuli and organic materials, such as amber, are not minerals. However, they are frequently used in jewelry and often considered to be a gemstone as well. Gemstones are considered valuable because of their luster or other unique physical properties, in addition to their rarity, which also lends value.
The world's foremost authority in gemology, the Gemological Institute of America was established in 1931, and is the world's largest and most respected nonprofit institute of gemological research and learning. They, along with other gemological organizations, have created gemstone classifications to aide in understanding and appreciating the characteristics of gemstones.
The first characteristic gemologists employ is chemical composition. For example, many gems are crystals, classified by a crystal system such as cubic or trigonal or monoclinic. Gemstones are classified into groups, species and varieties. For instance, ruby is the red variety of the species corundum, while any other color of corundum is considered a sapphire. Gemstones are also identified according to their hardness, luster, and refractive index.
While there is no set standard for grading gemstones, other than the diamond's 4 Cs, the GIA has created a system for choosing and purchasing gemstones. This system may help those interested in purchasing gemstones and understanding what makes one gem more valuable than another.
Gems and Color
Gems come in virtually every color of the spectrum. What may surprise some is that gems come in varying hues as well. The sapphire, for example, comes in blue, yellow and pink. Gem varieties such as tourmaline and garnet are available in almost every color. Prices for different gem varieties are affected by rarity, durability and popularity. Lesser-known gems are sometimes surprisingly beautiful and affordable.
For every gem, color is the most important value factor. Hue, tone and saturation are also important factors when considering a gem's value. Brighter, more vivid colors with a medium tone are the most sought after. A "grass" green gem is typically most valued, followed by pale celadon, lime or dark hunter green, which is less expensive. Very pale, very dark or brownish-hued gems are less valuable.
Gems and Light
Light is an important factor when considering the value of a gem. The color of most gems is affected by light sources. Blue sapphires often look best illuminated by a fluorescent light, while rubies look better under incandescent lighting. When choosing a gem, always examine it under different lights, especially the light it will be worn in most.
Gems and Clarity
The way gemstones form in the earth often creates inclusions, or in laymen's terms, a birthmark. The fewer inclusions in a gem, the rarer and more valuable it is. But inclusions are also responsible for the optical phenomena observed in many gemstones. For example, cat's-eye chrysoberyl and star sapphires, created by inclusions, actually increase the gem's value. In gemstones such as emerald and red tourmaline, the presence of inclusions and their lack of clarity does not detract from their value. Clarity has the most impact on value for gems with pastel colors because the inclusions are more visible to the naked eye.
Gems and Weight
Gems are sold by weight - measured in a carat, which is one-fifth of a gram. Therefore, buyers can expect to pay more per carat for a large stone than for a small one. Emeralds, rubies, sapphires, and alexandrite, for example, rarely occur in large sizes. Amethyst, citrine, blue topaz, and amber are more widely available in large sizes, so these gems have similar price per carat as smaller stones. To clarify, a one-carat emerald and one-carat ruby are the same weight but not the same size. Each is a different mineral with a different density. This difference in density also helps gemologists indentify gems.
Gems and Cut
While Mother Nature creates her gem masterpieces, it is the skilled gem cutter that releases a gem's brilliance and beauty. As gems handle light differently, their cut helps to create the unique optical properties of its crystal structure. The cut of a gem refers to the three-dimensional shape of the gemstone and the quality of the cutting, or how well the gem's shape delivers brilliance and beauty.
When judging the cut of a gemstone, examine how the stone returns light to the eye. Preferred cuts are symmetrical and return light across the entire surface of the gem.
Synthetic and artificial gemstones
Gemstones can be manufactured to imitate other gemstones. For instance, cubic zirconia is a synthetic diamond simulant. However, gemstones created in a lab are not imitations. Diamonds, ruby, sapphires, and emeralds are all manufactured in labs and can possess identical chemical and physical characteristics to the naturally occurring variety. These synthetic stones cost only a fraction of the natural stones. Natural gemstones are still considered more valuable because of their relative scarcity.
Lewis Jewelers is proud to carry the full line of Pandora Jewelry. Pandora bracelets, Pandora charms and Pandora beads are only a part of the collection. For more information, Lewis Jewelers, 2000 West Stadium Blvd., Ann Arbor, Michigan, 48103, 877-88-LEWIS or visit the website.