When shopping for an engagement or wedding ring, there is an art to choosing the highest quality gems.
With a treasure trove of diamonds and gemstones available and so many options to consider, couples can speed up the process by familiarizing themselves with some common characteristics and terminology.
A good place to start is to learn the Gemological Institute of America’s Four Cs — cut, color, clarity and carat.
Shoppers also should know a few terms: brilliance refers to the amount of white light a stone returns to the eye; inclusion refers to a gem’s internal qualities and whether mineral crystals or voids that can reduce value are present; and saturation refers to the intensity of the color.
But before looking at any gems, the first thing a buyer must do is decide on a budget, said John King, a gemologist and chief quality officer for the GIA’s laboratory in New York.
Having a price in mind will help the buyer decide which qualities are most important to them and whether they prefer a larger gem with more flaws or a smaller stone with better color or clarity, King said.
To make an accurate evaluation, leave the loupe to a credentialed jeweler, said King. “Find someone to work with who can guide you and help you understand the factors affecting the value of gems and jewelry,” he said.
When it comes to diamonds, less color often equates to a higher price tag.
The GIA grades the color of regular diamonds on a scale from D to Z. he highest rating is D, which indicates little or no visible coloration. Diamonds graded Z have the most color — usually a yellow or brown tint. But these colors are usually only apparent through a 10x magnifying jeweler’s loupe.
Some colors, such as pink or blue, are desirable and command a premium price. These very special diamonds “are rare and unique items that come in all colors of the rainbow, from soft pale to deep colors,” King said.
For other gems, such as rubies and emeralds, the hue or tone of a particular stone and the saturation of its color are key factors in determining value, said Douglas Hucker, a gemologist and chief executive officer of the American Gem Trade Assn. in Dallas.
Intense colors, such as those found in rubies, emeralds and sapphires, will normally command the highest prices, he said.
Look for vivid colors with a “medium” tone. For example, the most valued hue for an emerald is grass green, and rubies are most coveted when they are pure red. Sapphires are preferred in a strong medium blue rather than deep navy or pastel tones, Hucker said.
Clarity is a key quality for diamonds and measures how free a stone is from inclusions or birthmarks.
Diamonds are rated from flawless, for a stone that is nearly perfectly clear, to included, in which tiny inclusions interfere with the gem’s brilliance.
Almost all diamonds have some inclusions, birthmarks and surface blemishes, according to the GIA.
Although also valued for clarity, some colored gemstones can thank their lucky inclusions for making them more stunning and valuable.
These are called phenomenal gemstones, and produce such remarkable features as cat’s-eyes and stars in sapphires or rubies and a certain play of color in opals, said Hucker.
While color has the biggest influence on the price tag, experts say that the cut is the most important qualification for diamonds. Cut goes beyond the shape and style of a polished diamond to include the proportions, symmetry and polish of the stone. As stated in the GIA diamond-buying guide, “A well-cut diamond, with well-balanced proportions and high polish, can make light behave in breathtaking ways.”
Colored gems also can benefit from a good cut. Color and light should dance throughout a faceted gemstone, with no washed-out central window in the center or dead spots around the edges, according to experts with the American Gem Trade Assn.
The most common shapes for stones are round brilliant, oval cabochon and emerald or rectangular cut. Oval and cushion cuts bring out the best in the rare red-to-green color-shifting alexandrite gems.
Aquamarine, once believed to keep sailors safe at sea, sparkles in an emerald-cut shape.
Gems are sold by weight, which is measured in carats. A carat is one-fifth of a gram.
Some gems, such as ruby, tsavorite garnet and alexandrite, rarely occur in large sizes.
“The ruby, the queen of all gems, is rarely above 2 carats and increases exponentially in its rarity — and hence, cost — once it goes above 4 or 5 carats,” said Hucker. “Both sapphire and emerald can command very high prices per carat if they are fine quality, but they regularly come in larger sizes.”
Most gemstones are treated, usually with heat, to improve their color, Hucker said. Be skeptical of claims that a gem is untreated.
“A salesperson who makes claims that ‘all of our gems are untreated’ is either poorly trained or uninformed,” said Hucker. “Never buy a gemstone as untreated unless the jeweler has documentation to support the claim.”
To identify treated or synthetic stones, and to ensure the quality of your purchase, ask for certification for the diamond or colored gem, or get a report from an independent gemological laboratory, such as the Gemological Institute of America or the American Gem Trade Assn. This evaluation will confirm the identity, variety and natural origin of the gem.
Whether seeking out the perfect diamond or a dazzling emerald or ruby, using a credentialed jeweler and being educated about gems can help ensure you’re not banking on a bauble.
—Debra Beyer, Custom Publishing WriterCopyright © 2015, Los Angeles Times