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!

Election Day Sparkle

It’s election day in the USA! Months of election coverage culminates as America heads to the polls. We wanted to pay tribute to this important occasion in our own way: with red, white and blue jewelry designs from members of the American Gem Society (AGS). These beautiful pieces get our vote!

Red

Let’s begin with some bright and cheery red gemstones. Rubies naturally come to mind, but when it comes to red hues—there are many varieties of gemstones to choose from.

Jeffrey Daniels Unique Designs

jeffreydaniels-rubellite

A triangular rubellite set in 18k hammered gold, framed by bead set diamonds.


Supreme Jewelry

supreme-garnet

A red garnet pendant set in 18k rose gold framed by white diamonds.

United Color Gems

unitedcolorgems-red-spinel

Oval shaped red spinel earrings set in 18k white gold with white diamonds.

White

The color white has long stood for innocence, purity…and a color you’re not supposed to wear after Labor Day. But we all know diamonds and pearls can be worn any season!

Spark Creations

sparkcreations-diamond

These diamond earring jackets will give a simple diamond stud a little more oomph.

Honora

honora-pearls

The perfect balance between modern and feminine. White freshwater cultured pearls and sterling silver bracelet.

Caro 74

caro74-diamonds

Floral diamond pendant with a diamond bale, set in 14k white gold.

Blue

We can thank Mother Nature for some truly beautiful, truly blue gemstones! Be true blue with these wonderful designs!

Armadani

armadani-starsapphire

Star sapphire cabochon halo ring with round brilliant diamonds.

Carelle

carelle-tanzanite

Tanzanite Round Stack earrings in 18k yellow gold.

JB Star

A Passion for Precision.. A Labor of Love

Platinum pendant featuring a round diamond center encircled with perfectly matched round sapphires and pave accents.

No matter how you vote, when you choose to shop with a trusted AGS jeweler, you’re voting for a winner! Click here to search for an AGS jeweler near you.

September is for Sapphires

sapphiremulti003As we turn our calendars to September, we start thinking of things like heading back to school, indulging in a pumpkin spice latte, and planning our fall fashions. For those celebrating a birthday in September, they’re thinking of their birthstone: the sapphire!

Although sapphire typically refers to the rich blue gemstone variety of the mineral corundum, this royal gem actually occurs in a rainbow of hues. Sapphires come in every color except red, which would then be classified as ruby.

Trace elements like iron, titanium, chromium, copper and magnesium give naturally colorless corundum a tint of blue, yellow, purple, orange or green, respectively. Sapphires in any color but blue are called “fancies.”

Pink sapphires, in particular, tow a fine line between ruby and sapphire. In the U.S., these gems must meet a minimum color saturation to be considered rubies. Pinkish orange sapphires called padparadscha (from the Sri Lankan word for “lotus flower”) can actually draw higher prices than some blue sapphires.

Due to the remarkable hardness of sapphires—which measure 9 on the Mohs scale, second only to diamond—they aren’t just valuable in jewelry, but also in industrial applications including scientific instruments, high-durability windows, watches, and electronics.

Sapphires make stunning gifts for anyone born in September or celebrating a 5th or 45th wedding anniversary, so be sure to visit an AGS jeweler. They will help you find that perfect gift, whether you’re seeking the classic blue or another shade from the sapphire rainbow.

Need some inspiration? View this collection of designs featuring the sapphire!

Carelle

Carelle

The Whirl Sapphire Bangle by Carelle is 18k yellow gold with 1.06ct sapphire.

 

 

Michael Schofield & Co.

MichaelSchofield

Yellow sapphire and diamond earrings by Michael Schofield & Co.

 

 

Setaré

Setare

Sri Lankan sapphire earrings mounted in platinum and framed by diamonds, by Setaré.

 

 

Yael Designs

Yael

Yael Designs’ two-tone 18k gold pendant featuring a 1.59 carat pink sapphire, framed by pink sapphires and ideal cut diamonds.

 

Gumuchian

Gumuchian

Gumuchian’s Cloud 9 earrings are 18kt white gold set with blue sapphires and diamonds.

 

 

Ricardo Basta Fine Jewelry

RicardoBasta-Lilac

Lilac sapphire ring designed by Ricardo Basta Fine Jewelry. It’s surrounded by two diamonds and set in platinum.

 

 

Suna Bros.

Suna-StarSapphire

Star sapphire surrounded by diamonds, designed by Suna Bros.