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!

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

spinel-Gem2000

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

peridot-Gem2000

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!

Silver Shines On

By Robin Skibicki

The popularity of silver jewelry never seems to ebb, as designers are finding new and artistic ways to style the affordable and malleable metal. Whether silver is mixed with other metals or set with diamonds and gemstones, it’s a go-to look that complements a wide range of colors and styles.

For centuries, silver has been prized for its incredible luster and workability. In this industry, we naturally think of it as a versatile metal used to design beautiful jewelry. But it’s also applied towards technology and industry, used in the home, and often considered for investment purposes.

Pure silver is highly tarnish-resistant but is too soft to use for jewelry design. Other metals like copper, nickel, or zinc, are added to harden silver. For example, sterling silver is 92.5% silver and 7.5% another metal. Silver products sometimes may be marked “925” which means that 925 parts per thousand are pure silver.

Some jewelry may be described as silverplate: a layer of silver is bonded to a base metal. According to the law, quality-marked silver also must bear the name or a U.S. registered trademark of the company or person that will stand behind the mark.

If you’re looking for an inexpensive metal for your fine jewelry, silver is a good choice. Since silver is soft and scratches easily, it’s best used for jewelry that is not worn daily.

The versatile beauty of silver is showcased in these designs by our credentialed AGS members.

Michael Schofield & Co.

MichaelSchofield

A twin fish motif artfully decorates a sterling silver cuff.

 

Breuning

Breuning

Petals of silver and silver coated with yellow gold feature a sapphire center.

 

MK Diamonds & Jewelry

MKDiamonds

Sterling silver earrings featuring pear-cut blue topaz and blue sapphires set in black rhodium sterling silver.

 

Parlé

SONY DSC

Sterling silver Australian boulder opal and sapphire pendant.

 

Ed Levin Jewelry

edlevin.png

Sterling silver Secret Heart Bracelet “swings open” to reveal a secret heart.

If you’re in the market for silver jewelry—perhaps you like one of the designs pictured above—or have some silver jewelry that needs some TLC, visit a credentialed 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.