Six Displays of Optical Phenomena in Gemstones

By Robin Skibicki

There are several varieties of gemstones that display optical phenomena, which describes the many ways light interacts with the structural features or inclusions (internal characteristics) in the gemstone. Often these gemstones will be fashioned in a particular way that best displays these effects.

The science of optical phenomena can be fascinating, although the mystery and allure of these effects are what initially attract us! In this article, we’ll discuss six of the most familiar (and magical) displays of optical phenomena in gemstones.

Adularescence

Adularescence is the phenomena typically seen in moonstone, which is a member of the feldspar family. It produces a billowy soft blue to milky white light that appears to move across the gemstone. This occurs when light hits the alternating layers of albite and orthoclase, which are two differing forms of feldspar within the gem.

The layers of feldspar interfere with the light rays causing them to scatter and the eye to observe adularescence. The effect is best seen when the gemstone is cut en cabochon [en CAB-ah-shawn]—that is, with a polished, domed top and a flat or slightly rounded base.

 

Asterism

Asterism, or stars, relates to the four- or six-rayed star pattern of light produced by the fibrous inclusions, elongated needles, or growth tubes in a gemstone. This singular, celestial-like phenomenon is best seen in a gemstone cut en cabochon.

 

Chatoyancy

Chatoyancy [sha-TOY-an-cee] is also known as “cat’s eye.” Fine needle-like or fibrous inclusions within the gemstone are what causes this effect. Again, stones fashioned as cabochons display this effect the best.

 

Color Change

A small number of gemstones display the color change optical phenomena. Depending on the lighting environment, the color change appearance can vary due to the shifting wavelengths. The technical term for this is photochromism or photochroism; “color-change” is a lot easier to say!

The best-known color changing gemstone is alexandrite. When viewed in sunlight, it appears greenish. When placed under incandescent light, it appears reddish. Other varieties of color-changing gemstones include sapphire, garnet, spinel, diaspore, and tourmaline.

 

Labradorescence

Labradorscence [lab-ra-dor-es-cence] is an optical characteristic often seen in labradorite. The effect is a spectacular play-of-color that is metallic or iridescent, displaying blue, green, red, orange, and yellow. This is an interference effect within the gemstone caused by internal structures that selectively reflect only certain colors.

 

Play-of-Color

Play-of-color is created by a combination of diffraction and interference and is the result of the microstructure of opal: the chameleon of a thousand colors!

Opals are made up of many layers of small, stacked spheres of silica. These spheres diffract light, splitting it into a spectrum of colors. The layers of these spheres create interference allowing certain colors to dominate, depending on the angle the opal is viewed.

 

Are you ready to see some of these displays in person? Visit a credentialed AGS jeweler near you and ask to see some gemstones that exhibit optical phenomena!

The World of Colored Gems

By Gleim the Jeweler

The jeweler allows me to wear the sapphire blue lake on my finger, emerald green leaves around my neck, and take the citrine sunset with me wherever I go. Jewelry has become my daytime link to nature in an office with no windows. And if I have to work late, there’s nothing like diamond stars and a pearl full moon against an onyx night sky.

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“Gossip” emerald cut three stone rings by Goshwara.

This wonderful quotation, by author Astrid Alauda, perfectly expresses the emotional connection that has been provided by colored gemstones for thousands of years.

Fine colored gemstones have been revered throughout history. Gemstones have been imbued with the power to foretell events, strengthen memory, quicken intelligence, ensure purity, avert lightning, prevent intoxication, ensure happiness and are often equated to the fountain of youth.

What Defines a Colored Gemstone?

Colored gemstones are described as all the various gemstones except for diamonds. Only a select few of the vast number of minerals known qualify as gemstones. In order to become a gemstone, the mineral must be rare and beautiful and be durable enough to be worn as jewelry.

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Blue sapphire ring by AG Gems.

Precious vs. Semi-Precious Gems?

In the past, the term “precious” was used to describe diamond, emerald, ruby, and sapphire. The term “semi-precious” referred to all other gemstones. Today, most jewelers and gemologists agree that these terms no longer accurately reflect the true value of these gems. In particular, some species of colored gems, such as alexandrite or demantoid garnet, are so rare that they have been known to command prices exceeding those of emerald, ruby, and even diamonds.

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Alexandrite and diamond pendant by Omi Privé.

Gemstones generally can be grouped into three major clarity categories:

  1. Gems that are flawless or have very minor inclusions (e.g. aquamarines and amethysts)
  2. Gems that are moderately included (e.g. rubies and sapphires)
  3. Gems that tend to be highly included (e.g. emeralds and red tourmalines)

Color is the single most important deciding factor in determining the value of a gemstone, followed by the cut. The cut of a gemstone is designed to bring out the best possible color or colors in the rough uncut material while retaining as much weight as possible. The color in a fine gem is saturated evenly throughout the stone and is of a brilliant deep, rich, and pleasing color—not too dark and not too light.

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Indicolite earrings by Erica Courtney.

Each variety of colored gemstone has a range of highly prized colors that have evolved over the years. Many of these colors are tied to historical sources such as “Burmese” rubies from Burma, “Kashmir” sapphires from India, and “Persian” turquoise. This is by no means a sure bet. Not all rubies from Burma have the “Burmese” signature color and furthermore, you may find a fine color from a ruby that was mined in Thailand.

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Cushion cut Mozambican Ruby ring by Real Gems Inc.

Ultimately the wearer decides what color speaks to them, keeping in mind that this may not be that color defined as being the most valuable. Since we all perceive color differently it’s ultimately a very personal choice.

Today, with the ever-increasing advances in gemstone enhancements and synthetic gemstone production, it is more important than ever to work with a reputable and properly trained jeweler.

About Gleim the Jeweler

We have been serving the Peninsula since 1931 and have been members of the American Gem Society (AGS) since 1954. Our membership with the AGS assures you that we earn and maintain the education necessary to provide you with the most up to date information about gems and their different markets.

We also have American Gem Society Accredited Gem Laboratories, assuring you that we have the proper instruments to identify and grade gems. And, what’s perhaps most important, we love colored gems!

August’s Trio of Distinctive Gemstones

It’s been a year since spinel was added to August’s birthstone line up. Those celebrating a birthday during the eighth calendar month now have three gemstone choices: peridot, sardonyx, and spinel.

Spinel

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Blue spinel by Gem 2000.

For those who are still unfamiliar with spinel, it is often assumed to be other gemstones, like ruby or sapphire.  Cobalt blue, like the one above, is one of the most desired colors. But it can be found in a variety of colors, such as the much coveted red, as well as black, violet blue, greenish blue, grayish, pale pink, mauve, yellow or brown. Spinel can also be found in various cuts, like octagons, trillions, squares, rounds and fancy shapes, like ovals, pears, and cushions.

No matter what the shape, spinel is spectacular! Take a look at these designs by our AGS members. Click on the images for a closer view.

 

Peridot

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Peridot by Gem 2000.

The verdant peridot is the gemstone most commonly associated with August. Peridot’s recognizable green hue could sometimes vary from yellowish-green to olive to brownish green, contingent on how much iron is present. Yet the finest peridot is a brilliant green without any hints of brown or yellow.

Our AGS members will help you find the perfect peridot for you! Click on the images for a closer view.

 

Sardonyx

Sardonyx

Since as far back as Roman times, sardonyx has been highly valued as a stone representing strength, courage, happiness, and clear communication.

The unique reddish, zebra-striped banding of sardonyx stands out beautifully when the stone is smoothed, so it is often cut in cabochon and worn as beads or featured in an eye-catching pendant or ring.

Sardonyx makes a great gift for those born in August who want something a little different than the traditional birthstone. Readily available and relatively inexpensive, sardonyx makes an affordable addition to anyone’s collection.

If you’d like to add spinel, peridot, or sardonyx to your jewelry wardrobe, contact a credentialed AGS jeweler near you!

3 Stone and Jewelry Trends from the 2017 Tucson Gem Shows

By Jennifer Heebner, Guest Writer

Like tourists to the Grand Canyon, thousands of people routinely descend on Tucson, Arizona, in the first quarter of every year. The reason? Gemstones!

An annual gathering of miners and cutters that is loosely dubbed the “Tucson Gem Shows” is the draw, with 40-plus individual fairs targeting largely professional buyers of rough and loose stones and some finished jewelry.

While some venues permit entry to consumers, the bulk of the shows exist to serve the business-to-business audience. As a longtime member of the trade, the American Gem Society secures entry to the toniest destination in town—the American Gem Trade Association’s GemFair Tucson, held Jan. 31 to Feb. 5—to find out what AGS member artisans brought for your favorite stores to buy.To wit, here are three trends that you can shop by fall.

To wit, here are three trends that you can shop by fall.

Colored gemstone halo style engagement rings. You’re accustomed to seeing all-diamond halo-style rings in stores, but colored stone merchants are getting in on this style game with their own vivid versions. Think naturally color-changing alexandrite melee surrounding purple spinel at OMI Gems, or multiple hues of fancy color sapphires. These options are fresh in terms of look and can also help contain costs, depending on the gems. “Young couples are really interested in color for engagement rings—and not just blue!” observes Kambiz Sabouri, president of Gem 2000.

Omi Prive Alexandrite

Ring with a purple spinel center stone and a halo of diamonds and alexandrite from OMI Gems.

Unexpected color combinations. From rare pink Mahenge spinels with Mozambique ruby to opals with tsavorite or mandarin garnet, there are no rules for robust and beautifully colored gem pairings. In fact, Royal India isn’t creating anything that could be considered a basic look anymore; instead, it is making one-of-a-kinds. “People are tired of being ‘dull,’” remarks CEO Vishal Kotahwala. Helping to grow the numbers of sui generis? Rare stones like Paraiba tourmaline. “Paraiba with anything is wonderful,” notes Sabrina Bindra, director of sales and marketing for B & B Fine Gems.

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Earrings with mixed colors of gemstones from Royal India.

Long necklaces for layering. Length remains a go-to for many fine jewelry-buying fashionistas. Versatility is one reason—heard of layering?—but so is a variety of materials. Long necklaces from pearl maker Mastoloni feature not just round or baroque shapes of South Sea pearls but also gemstone accents. And at Jye’s International, lightweight numbers, particularly 36-inch-long necklaces with rose-cut sapphires, are most in demand. “The younger generation loves to mix up their wardrobes with functional pieces,” says founder Jennifer Chang.

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Multi-strand necklace with rose-cut multi-color sapphires from Jye’s International.

Want to learn more about these gemstones and trends? Do you have your own designs in mind? Visit an AGS-certified jeweler near you and they’ll be happy to help you find the gems and look that’s right for you!

Five Trends to Look for at the 2017 Oscars

If you haven’t already, be sure to mark your calendar for this Sunday, February 26, so you don’t miss the 89th Academy Awards! Millions of film and fashion fans will be tuning into ABC at 7:00 p.m. EST/4:00 p.m. PST when the stars begin to walk the red carpet.

What will this year’s fab fashions be? Here’s a list of five trends that are predicted to be “scene” on the stars. We’ve included a few designs from AGS members that we think would best complement these lovely looks.

Flowers and Nature

Floral designs never seem to go out of style and with spring just around the corner, what better place to display some flower power than at the Oscars! They can either be classic and demure or big, bold, and bright! With the growing trend of floral patterns, other nods to nature are sure to follow. Animals, birds, and leafy plants are leaving a trail on this season’s designs.

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Sapphire, white and brown diamonds flower ring by Supreme Jewelry.

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Flexible diamond tiger cuff
by Roberto Coin.

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Cobra drop earrings with diamonds
by John Hardy.

Pink

Here’s a hue that has been popular of late. When it comes to pink gemstones, we can choose from pink diamonds, pink sapphire, Morganite, kunzite, and rose quartz, to name a few! Which gal—or guy—will be thinking pink on the red carpet?

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Fancy light purplish pink heart shape diamond necklace by Scott West Diamonds.

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Fancy pink diamond ring by
Jeffrey Daniels Unique Designs.

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Pink sapphire flower cluster diamond earrings and pendant by Whiteflash.

One Shoulder

The elegant drape of a one-shoulder dress or top embodies a mix of sophistication and sultriness. An ensemble like this should be punctuated by some serious sparkle!

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Diamond Angel Feather ring
by KC Designs.

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The Helen necklace by Harry Kotlar.

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White Kites Bird long earrings
by HOF X Stephen Webster.

Satin

Reminiscent of old Hollywood, satin is one of the biggest trends this spring. Expect to see the silky-smooth and shimmering fabric in bright jewel tones. Enhance the look with gorgeous jewels like these!

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Trillion cut Tanzanite and diamond earrings
by AG Gems.

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A two-tone gold necklace featuring rose-cut emeralds and diamonds by Yael Designs.

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Paraiba tourmaline and diamond ring by Takat.

Color Blocks

Gone are the days of drab black and gray. Enter the brilliant and daring blocks of color! Bold and beautiful gemstones make these jewelry designs absolute showstoppers.

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“Amazon” pendant featuring peridot accented by purple garnet and diamonds by Erica Courtney.

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“Gossip” emerald cut citrine earrings with diamonds by Goshwara.

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Rhodolite and spessartite garnet ring
by Omi Prive.

Shopping for fine jewelry should be just as exciting as the Oscars but without unwelcome surprises. American Gem Society (AGS) credentialed jewelers adhere to standards that not only comply with governing laws, but that go beyond, to ensure that you are buying from jewelers who have the knowledge and skill to help you make the most informed buying decision. To find an AGS jeweler near you, click here, and leave the nail-biting uncertainty for the Oscars!

Four Fun Facts About January’s Gemstone

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Rhodolite garnet and emerald sunbeam earrings by Ricardo Basta Fine Jewelry.

If you’re celebrating a birthday or any special occasion this month, then the garnet is a worthy addition to your fine jewelry wardrobe. Here are four fun facts about the colorific January gem:

1. Not all garnets are red.

Garnet is actually the name of a group of minerals that comes in a rainbow of colors, from the deep red of the Pyrope garnet to the vibrant green of Tsavorites. Some rare garnets are even blue, colorless, or—most rare of all—change colors in different lights. But the most common color is a beautiful range of reds, from rust colored to deep violet-red.

2. It’s more than just a gemstone.

For thousands of years, the garnet has lived a glamorous life as a gemstone. But in the past 150 years, it has also been put to the test as an effective industrial mineral. In the United States, garnet has been utilized for waterjet cutting, abrasive blasting, and filtration.

3. Their inclusions make them unique.

Some garnets have inclusions that are part of the beauty of the overall stone (like “horsetails” in Demantoid garnets, or Hessonite garnets which sometimes have a “turbulent” look). So you may discover that you like the distinctive look these inclusions bring to the piece.

4. Garnets have been around for a very long time.

The garnet is so durable, remnants of garnet jewelry can be found as far back as the Bronze Age. Other references go back to 3100 BC when the Egyptians used garnet as inlays in their jewelry and carvings. The Egyptians even said it was the symbol of life. The garnet was very popular with the Romans in the 3rd and 4th Century.

Today, the garnet can be found in a range of jewelry pieces and styles, from beautiful rings to stunning tiaras. Since the garnet can come in a range of colors, rare garnets in green or blue make breathtaking pieces, especially in pendants or drop earrings.

Here are a few designs from AGS members featuring the many colors of the garnet. Click on the images for a larger view.

To learn more about the wide range of garnet color options and to pick the perfect piece, search for an AGS jeweler near you!

October’s Birthstones are Bursting with Color

octoberbirthstonesOctober features two incredible birthstones: opal and tourmaline. They each display an exciting and intense array of colors, making them popular choices for jewelry designers and collectors.

Opal

The name “opal” derives from the Greek Opallos, meaning “to see a change (of color).” They range in color from milky white to black with flashes of yellow, orange, green, red, and blue. An opal’s beauty is the product of contrast between its color play and its background.

Opal is a formation of non-crystalline silica gel that seeped into crevices in the sedimentary strata. Through time and nature’s heating and molding processes, the gel hardened into the form of opals. The opal is composed of particles closely packed in spherical arrangements. When packed together in a regular pattern, a three-dimensional array of spaces is created that gives opal its radiance.

Approximately 90 percent of the world’s precious opal comes from Australia. The following are other countries that produce precious or fancy varieties: Brazil, Mexico, United States, Hungary, Peru, Indonesia, Honduras, Guatemala, Nicaragua, Slovakia, Czech Republic, and Ethiopia.

Like fingerprints, each opal is totally unique! To get a really good look at the opals in these designs, click on the images below for a larger view.

Lightning Ridge Collection

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Blue-green black opal accented by fine white princess cut diamonds and round brilliant cut diamonds.

 

Lika Behar Collection

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Sterling silver and 24k gold “Ocean” necklace, featuring a one-of-a-kind boulder opal framed by diamonds.

 

Parlé

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Australian black opal and diamond earrings set in 18k yellow gold.

 

Yael Designs

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An 18k rose gold bracelet featuring rose cut fire opals and brilliant cut white round diamonds.

 

Tourmaline

Since tourmaline is available in a wide variety of colors, it is ideally suited to almost anyone’s taste. It is known for displaying several colors in the same gemstone. These bi-color or tri-color gems are formed in many combinations; the gemstones with clear color distinctions are highly prized.

One multi-color variety is known as watermelon tourmaline and features green, pink, and white colors bands. To resemble its namesake, the gemstone is cut into thin slices having a pink center, white ring, and green edge.

Tourmaline is found in many localities including Brazil, Afghanistan, East Africa, and the USA.

The following designs feature the varying hues of tourmaline. Click on the images to see a larger view.

 

Erica Courtney

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“Rain Drop” 18k yellow gold studs featuring
Paraíba tourmaline accented with diamonds.

 

Supreme Jewelry

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This unique ring displays a butterfly fluttering around petals of  sliced tourmaline, framed by diamonds.

 

Omi Privé

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A cushion cut pink tourmaline and diamonds are set in platinum and 18k rose gold.

 

Crevoshay

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“California Dreaming” is an 18k gold pendant artfully displaying the many colors and varieties of tourmaline.

On behalf of everyone at AGS, we send our best wishes to those celebrating a birthday or anniversary in the month of October!

If you are shopping for opal or tourmaline jewelry, search for an AGS credentialed jeweler near you: www.americangemsociety.org/en/find-a-jeweler.