Gemstone Buying Guide
from Overstock.comIs there magic in your jewelry box among those jeweled rings? Ancient cultures believed gemstones had supernatural properties -- lapis lazuli protected the wearer against the evil eye, and amethyst produced a sober mind -- and who are we to disagree? Gemstones still enchant us with their sparkling color.
The most prized and famous gemstones are diamonds, emeralds, sapphires, rubies and pearls. This gemstone buying guide offers basic information about the colored gems (be sure to read our diamond and pearl guides, too). Once you learn how to buy gemstones, you're on your way to collecting a rainbow of brilliant jewels.
Just another pretty rock? Defining gemstones
A gemstone is a mineral or organic substance with a beauty that is highly valued by humankind. They have intense color, are durable enough to be formed into decorative art and are rare enough to retain high monetary value and public curiosity. These valuable stones are known as gems, gemstones and jewels.
There is no scientific or geological definition for ''gem'' or ''jewel'' -- these are human concepts. Minerals are formed by geological processes which happen continuously deep inside the Earth. When people excavate certain minerals and carve them into specific shapes, they become gems/gemstones. When placed in a decorative setting for wearing, gems become jewels.
Gemstone color groupings
Scientists group minerals, including gems, by their compositional properties, which are created by geological processes. However, professional jewelers, enthusiastic hobbyists and consumers appreciate these stones mostly for their astonishing colors.
Black: Jet, hematite, obsidian, onyx and schorl (a tourmaline)
Blue or violet: Amethyst, aquamarine, blue topaz, blue lace agate, iolite, lapis lazuli, sapphire, sodalite, tanzanite and zircon
Green: Apatite, bloodstone, chrome diopside, emerald, green amethyst, jade, malachite, peridot, serpentine, tashmarine and tsavorite garnet
Red or pink: Coral, garnet, jasper, kunzite, morganite, pink sapphire, pink topaz, rhodolite, rose quartz, rubellite, ruby and spine
White and iridescent: Ivory, labradorite, milky quartz, moonstone, mother of pearl, opal, pearl, rock crystal and white topaz
Yellow, orange or brown: Amber, aventurine, carnelian, chrysoberyl, citrine, fire opal, heliodor, padparadscha, smoky quartz, tiger's eye and topaz
Enhancing gemstones
Just as other natural materials such as cotton and wood are treated and processed for consumer use, most gemstones are enhanced to improve upon their natural qualities; some treatments, like heating, continue the naturally occurring process at work when gemstones are formed in the earth. These treatments, called enhancements, increase the availability and affordability of the vast and varied assortment of colored gemstones. Every jewelry description at Overstock.com includes gemstone treatment codes. More information on these treatments can be found in our gemstone treatment guide.
These are the most common designations for gemstone enhancement:
Enhanced (Code E): Some gems are routinely enhanced with a particular method that strengthens naturally occurring weaknesses. For example, most sapphires are heat-treated, and a heat-treated sapphire would have the enhancement code of E. A gemstone treated with a method other than the expected one will declare that method's code.
Natural (Code N): A gemstone that has not been enhanced is considered to be a natural stone, also called an untreated gemstone. The only changes to the gemstone's appearance come from the cutting and polishing processes.
Created (Code CR): Any gem that is labeled as "created" or "synthetic" was created in a laboratory. Created or synthetic gemstones have the same properties as their natural counterparts. However, the "faux," "imitation" and "simulated" gemstones are not created versions of actual gemstones and are often made of plastic. If you are in doubt, ask the vendor to clarify the origins of the gemstones.
Coating (Code C): Coating involves the use of surface treatments such as films and lacquers to create color and special effects.
Doublet (Code DBL): A doublet is a thin layer of natural stone adhered to a backing material. The doublet backing material is used to thicken and give strength to the gem.
Dyeing (Code D): The introduction of coloring matter into a stone gives it a new color or greater intensity of color.
Heating (Code H): Heating gemstones can clarify and change color or create special effects.
Irradiation (Code R): Altering gem color by neutron bombardment is called irradiation. This process creates residual radioactivity and such stones must receive a Nuclear Regulatory Commission safety release prior to sale. This enhancement method is often used in combination with heating treatments.
Oiling (Code O): Oiling involves the intentional filling of surface-breaking cavities and cracks in gemstones with a colorless oil, wax, resin or manmade unhardened resin.
Waxing (Code W): Filling in a porous opaque gem with colorless wax, oil or paraffin improves the appearance.
Gemstone care
A solution of water and a few drops of mild dish soap can be used to clean most gemstone jewelry. Clean the settings with a soft toothbrush and brush gently to avoid scratching the metal sections. Rinse with fresh water and dry the jewelry with a soft cloth. On the other hand, the organic gemstones and certain opaque stones like turquoise and lapis lazuli cannot be soaked for cleaning as they are porous and absorb water. Clean this jewelry by wiping it with a damp cloth after every wearing.
How are gemstones evaluated for quality?
Colored gemstones, like diamonds, are classified and evaluated by the "Four Cs": color, carat weight, cut and clarity.
Color is the most important factor in evaluating gemstones, and those with the most vivid colors usually command the highest price. Specific gemstones only occur in certain color ranges, based on their chemistry. When evaluating color, measure a gemstone against others of its kind.
Carat weight is defined by the formula 1 carat equal to 200 milligrams; a carat is divided into 100 points and each point is 2 milligrams. Heavier gems are more rare and expensive than smaller ones. Rarity of large stones also depends on the type; for example, the world's largest cut ruby weighs just over 23 carats, while the largest cut topaz weighs just less than 23,000 carats. Carat measures the stone's weight, but the crystal structural and other chemical properties can affect density, meaning two stones of the same size may have different weights. For this reason, colored gemstones are often listed by size instead of weight.
Cut accentuates the color of a stone by means of precise angles and proportions. There are many traditional cuts -- round brilliant, oval, emerald, square, princess, cabochon, pear, marquise -- and jewelers continue to look for better ways to show off their gems. A quality cut can be the difference between a good stone and one that is breathtaking.
Clarity describes the inclusions or flaws existing in all natural stones -- it is part of the proof of their natural origin. Fewer flaws mean a more valuable stone. Inclusions can also help determine if a gemstone has been treated. As with other factors, clarity is related to type. Some gems usually occur with few or no inclusions, while others are known for them -- a flawless emerald would be nearly priceless while flawless aquamarines are more common. As with diamonds, 10x magnification and a well-trained eye are used by gemologists to evaluate clarity.
Why are some gems called sapphires when they are not blue?
Although the word "sapphire" is most often associated with the color blue, sapphire features many colors. Sapphire is the gem name for the mineral corundum, and sapphires can be pink, yellow, green, orange, black and white. Certainly, the most prized color is the legendary clear, vibrant blue. Gemologists call almost all gem-quality corundum sapphire. The two exceptions to this general rule are rubies and padparadscha stones. Rubies are red corundum and padparadschas are corundum with a rare pink-orange color (not to be confused with pink sapphires and orange sapphires).
Why are some gemstones called precious and others called semiprecious?
For many years, colored gems were known as the precious and semiprecious stones. Rubies, sapphires and emeralds were called the precious stones because their rarity made them the most desirable gems among the wealthy who could afford a brooch, cameo, necklace or other bejeweled item. Other popular gems became known as semiprecious, which, unfortunately, hinted that these gemstones were sub-standard. As gemstones become more widely available, many of today's jewelers try to avoid these terms. In fact, a high-grade semiprecious gem can be more valuable than a low- or medium-grade precious stone.
What are organic gemstones?
Organic gemstones are natural substances that are used for jewelry and other decorative arts but are not derived from mineral stones. The term most commonly refers to pearls, amber, coral and jet.
Uniquely colored gems
Spice-up your gemstone jewelry with colors beyond the common reds, yellows and blues. Many stones are bi-colored or tri-colored; others, like tiger's eye and malachite, have fascinating patterns. Settings of large stones display these gems vividly in a pendant or bangle; beaded patterns form a pretty necklace or bracelet.
Consider adding these unusual stones to your collection:
Ametrine: This gemstone contains both amethyst and citrine sections. The resulting purple and yellow coloration adds a regal look to a jewelry collection when set in yellow or white gold.
Bloodstone: Red iron oxide spots add visual interest to this dark green chalcedony gem. It is popular in handcrafted world jewelry.
Fire opal: These opals feature fiery red, orange and yellow colors; they are also called Mexican opals.
Lapis lazuli: Shiny yellow flecks distinguish these dark blue stones that have been used for decoration for many centuries.
Watermelon tourmaline: These tourmalines have pink centers and green borders, though the color pattern is sometimes reversed. The cut stones are stunning gems, especially when set in pendants or large rings.
A world of gemstone jewelry
Talented artisans continue to create distinctive sterling silver and gemstone jewelry in city and village shops all over the world. Overstock.com is excited to offer you this handmade jewelry in our Worldstock Store. Some designs are universal and others are unique to the local culture -- each pendant or earring reflects the pride of dedicated men and women.
Remember my birthday and my birthstone
Every gemstone guide needs a birthstone list -- it helps us find the perfect jewellery gifts for loved ones. Moms and Dads often introduce young girls to jewels with pretty birthstone jewelry sets. Grown-ups will find their birthstones in many handsome necklaces, earrings and rings for both men and women.
Birthstones also remind us that gems are nature's beautiful treasures. For centuries, people associated gemstones with magical qualities, seasons and birth months. Let these brilliant gems, pulled from the earth just for you, bring good fortune or, at least, a cheerful dose of color to your life.
Modern birthstones by month:
January: Garnet
February: Amethyst
March: Aquamarine
April: Diamond
May: Emerald
June: Pearl, moonstone or alexandrite
July: Ruby
August: Peridot
September: Blue sapphire
October: Opal, pink tourmaline or rose quartz
November: Citrine or yellow topaz
December: Blue topaz, turquoise or zircon