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.

PC1116ALTR-AlexandriteDiamondPendant

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.

Idolite earrings

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!

June Hits the Birthstone Trifecta

By Robin Skibicki

Those born in June celebrate their special month with three beautiful birthstones: the luminous pearl, enchanting alexandrite and magical moonstone.

June-Trifecta-hz

Pearls

Pearls are the only gemstone in the world that comes from a living organism, and can be found in both saltwater and freshwater. Whether natural or cultured, a pearl forms when a mollusk produces layers of nacre (pronounced NAY-kur) around any type of irritant inside its shell. In natural pearls, the irritant may be another organism from the water. In cultured pearls, a mother-of-pearl bead or a piece of tissue is inserted (by man) into the mollusk to start the process. There are also different types of mollusks that produce very different looking pearls.

For centuries, pearls have been a symbol of beauty and purity. Today, they are regarded as both classic and contemporary, coming in many more fashionable styles than your grandmother’s traditional strand of pearls.

 

Honora pearl and rock crystal

Sterling silver necklace with five rows of white baroque coin freshwater cultured pearls and rock crystal, by Honora.

 

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Mastoloni designed a 16.3mm Tahitian pearl set in 18kt white gold adorned with diamonds on each side.

 

Shogun Pearl e241

Natural golden South Sea cultured pearl and diamond earrings in 18kt gold, by Shogun Pearl.

 

Alexandrite

This variety of color change chrysoberyl is extremely rare, placing the alexandrite in its own mineral group. When this remarkable stone is viewed in daylight or fluorescent light, it appears green or blueish green. When seen under incandescent lighting, it morphs to a purplish red.

Due to its rarity, some jewelers stock synthetic versions of this chameleon-like gemstone. Synthetic gemstones are man-made alternatives to the natural material, possessing the same physical, optical, and chemical properties as the natural gemstone.

Alexandrite is a relatively modern gem, first discovered in Russia around 1831 during the reign of its namesake, Czar Alexander II. Although alexandrite has a short history, it is has been associated with good fortune, enhanced creativity and focus.

The photos below are key examples of the incredible color-changing properties of the alexandrite. OMI Privé‘s, Niveet Nagpal, designed this bewitching brooch named “Alexis.” Each photo shows the same brooch under both color phases.

Alexis-duo

The lizard’s body is 18K white gold, and the back is made up of 6.06 ctw of alexandrite rough. The eyes are tsavorite, the mouth is ruby, and the entire piece is accented with diamonds, alexandrites and black diamonds. A work of art!

AG Gems Alexandrite

A natural, oval-cut Alexandrite ring by AG Gems is flanked by two half-moon cut diamonds and accented by 42 round brilliant cut diamonds.

 

Moonstone

A phenomenal gemstone, moonstones show a floating play of light (called adularescence) and occasionally show either a multi-rayed star or a cat’s eye. They are part of the family of minerals called feldspar and occur in many igneous and metamorphic rocks. Moonstone is a translucent stone that comes in a variety of colors, such as white, gray, green, blue, peach and champagne. The most popular is the rainbow moonstone, which is an iridescent white or gray displaying a blue sheen in the light. To enhance the adularescence, moonstone is often cut into a smooth cabochon shape.

Moonstone lore appears in varying cultures over the centuries, each associating its mesmerizing properties with goddesses, psychic abilities, femininity and motherhood, calming, protection, health and good fortune. Here are some exquisite designs featuring the magnificent moonstone.

 

Moonstone LikaBehar-1

The Pompei Pendant by Lika Behar Collection features a tear drop rainbow moonstone framed by 24k gold and oxidized sterling silver.

 

Moonstone yael-earrings

Yael Designs‘ Moonrise earrings are set in 18k white gold, and feature moonstones and blue sapphires, accented with ideal cut diamonds.

 

Moonstone-peach Ritani

A round, peach moonstone pendant by Ritani is set in 18kt yellow gold with a beaded edge finish.

 

If you’re in search of pearl, alexandrite or moonstone jewelry, visit our Find a Jeweler search for an AGS credentialed jeweler near you.

City Spotlight: Los Angeles

By Randi Molofsky

This new semi-regular feature will highlight some of our members’ favorite places to go and things to see in their hometowns, as well a sneak peek at their newest designs. First up: Los Angeles, where Michael John Jewelry and OMI Privé are headquartered.

Michael John Jewelry’s, Michael Hezar

Michael Hezar

Michael’s favorite Los Angeles…

  • RestaurantNobu Malibu
  • MuseumGetty Villa in Malibu
  • Shopping – I like the new and up-and-coming designer brands available at Barneys.
  • Weekend activity – My family and I live and breathe soccer and it pretty much occupies most of our time spent on the weekends. My wife, Atousa, and I have two boys and we are either at one of their tournaments, playing with them one-on-one or watching it together on TV.
  • Day trip – I love to visit Santa Barbara for relaxing and taking trips up to Big Bear for skiing with the family.

We love Michael John’s creations for their bold silhouettes and fashion-forward designs. Some of the designer’s newest pieces include a major pink diamond ring perfect for the ultra-feminine bride and a set of rose-cut diamond pieces that have more than enough sparkle for a night on the town.

Michael John Jewelry 5.70 carat pink diamond ring in 18k rose gold.

MJ pink diamondMichael John Jewelry rose-cut and round diamond ring in 18k white gold
and 39.61 carat rose-cut diamond bracelet in 18k white gold.

MJ ring bracelet
Founders, designers and brothers Michael and John Hezar, of Michael John Jewelry (formerly known as Michael John IMAGE and Image Jewelry), share a common goal of creating timeless fashion. Inspired by nature, these brilliant designs are crafted into impeccable jewelry with exquisite quality, allowing Michael John Jewelry to meet, if not surpass their goal of embracing everlasting style in all of their pieces.

OMI Privé’s, Niveet Nagpal

Niveet Nagpal

Niveet’s favorite Los Angeles…

OMI Privé designs out-of-this-world colored stone jewelry in classic settings with a twist. New favorites include this stunning purple spinel ring with a surprising alexandrite halo, and an oval aquamarine set in unexpected rose gold.

OMI Privé spinel and alexandrite ring in 18k rose gold.OMI spinel

OMI Privé aquamarine and diamond ring in 18k rose gold.OMI aqua

The Omi Gems family dates back five generations to Burma in the early 1900s. Decades of wars and close escapes from political unrest followed. With a handful of gems, a brilliant outlook, and a clear mindset, Omi Nagpal and his loving wife, Preeti, came to the United States. There, they founded and built a loose gemstone house that over time became synonymous with the world’s most valuable jewels. Now, the Los Angeles-based company is led by Omi’s son, Niveet. As head designer, Niveet has continued the family’s reputation and high integrity through the Omi Privé fine jewelry collection.

Pearls of Wisdom for June 2015

By Amanda L Colborn

Happy birthday to all the June babies out there!

You’re all very lucky in that you have three very unique birthstones commemorating this special month! Unfortunately, I am not creative enough to also be able to work “Alexandrite” and “Moonstone” into this blog’s title.

But, let’s jump right into pearls!

PEARLS

Historically, pearls have been used as an adornment for centuries.  They were one of the favorite gems of the Roman Empire. Later, during the Tudor period in England, the 1500’s were known as the Pearl Age.

Pearls are unique as they are the only gems from living sea creatures and require no faceting or polishing to reveal their natural beauty. In the early 1900s, the first successful commercial culturing of round saltwater pearls began. Since the 1920s, cultured pearls have almost completely replaced natural pearls in the market though we are seeing a strong revival of natural pearls.

Natural Pearl Necklace from Matoloni Pearls

Natural Pearl Necklace from Matoloni Pearls

Pearl Necklace from Mastoloni Pearls

Pearl Necklace from Mastoloni Pearls

ALEXANDRITE

A relatively modern gem, Alexandrite, was first discovered in Russia in 1831 during the reign of its namesake, Czar Alexander II, and is an extremely rare Chrysoberyl, with chameleon-like qualities.

Its color is a lovely green in both daylight and fluorescent light; it changes color to a purplish red in incandescent light.  Due to its rarity, some jewelers stock synthetic versions of this enchanting gemstone.  (Synthetic gemstones are man-made alternatives to the natural material, possessing the same physical, optical, and chemical properties as the natural gemstone.)

Here we have a video featuring a rare 6 carat Alexandrite ring from AG Gems:

A close-up of an Alexandrite Ring from AG Gems

A close-up of an Alexandrite Ring from AG Gems

MOONSTONE

The third birthstone for June is the Moonstone.  It was given its name by the Roman natural historian Pliny, who wrote that moonstone’s appearance altered with the phases of the moon — a belief that held until well after the sixteenth century.

A phenomenal gemstone, moonstones show a floating play of light (called adularescence) and sometimes show either a multirayed star or a cat’s eye. Considered a sacred stone in India, moonstones often are displayed on a background of yellow (a sacred color) and are believed to encapsulate within the stone a spirit whose purpose is to bring good fortune.

Part of the family of minerals called feldspar, moonstone occurs in many igneous and metamorphic rocks and comes in a variety of colors such as green, blue, peach, and champagne. The most prized moonstones are from Sri Lanka; India, Australia, the United States, Mayanmar, and Madagascar are also sources.

Moonstone

Moonstone

On behalf of everyone at the American Gem Society — we wish you a very happy June, full of joy and jewels!