Precious opal may seem to contain every color in the rainbow, depending on which angle you look at it. This color-changing phenomenon, known as iridescence or color play, has captivated imaginations for centuries. Thanks to its flashing colors, often resembling the flecks in irises, it has been thought to bring good luck and heal to eye ailments. Other cultures associate it with bad luck and the evil eye. Not surprisingly, perhaps, it’s been employed in Rorschach-type tests in psychology.

Opal, made of hydrated or hardened silica gel, is 5 to 30 percent water, which means the stone may eventually dry out, causing it to lose its iridescence and crack. Iridescence is created by the structure of the stone, wherein tiny, tightly packed silica spheres diffract light. The bigger and more orderly these spheres, the more color the opal appears to contain.

An amorphous stone, opal is formed in the cavities of sedimentary rocks such as ironstone and sandstone. It also creates veins in igneous rocks, is found in stalagmites or stalactites in caves, and works as a petrifying agent, replacing wood, shell, and bones in fossils. Before the 19th century, Czechoslovakia was the primary source of precious opal, but these days it’s Australia. Opal is also mined in Brazil, Ethiopia, Honduras, Indonesia, Japan, Mexico, Peru, Russia, southern Africa, and in Nevada and Idaho in the United States.

Being a soft, fragile stone, opal is easy to damage and difficult to work with. Nonetheless, jewelers find its enchanting color difficult to resist. Opal is often cut into cabochons with free-form shapes that best show off the color play within. These unique shapes inspire much creativity in the jewelry design for necklaces, rings, and bracelets. Opal may be opaque to translucent to transparent. It comes in a wide range of base colors, and generally has a vitreous luster.

There are both precious and non-precious types of opal. Perhaps the most well-known of the precious is called white opal, which has a light-colored based such as white or cream and intense color play. These opals may appear washed out without a closed-back bezel setting, which bring out their iridescence.

Even more rare and desirable, though, is black opal, which has a higher carat price than white. Black opal is actually a dark-colored opal, which can be gray, blue, green, or gray-black. Less dark is the precious jelly or semiblack opal, which has a lighter base in similar colors, and may have an amber color body that creates a stunning blue-purple iridescence.

Especially rare forms of precious opals include harlequin opals (transparent to translucent opals with mosiac-like patches of color), crystal opals (completely transparent and gl...

Sometimes the matrix rock, or mother rock, like ironstone or sandstone creates bands or inclusions inside the opal. Some opal is cut to highlight such inclusions, but boulder opal is cut so the stronger matrix stone is only on the back of the cabochon, making the piece both more resilient and cheaper to purchase. Andean opal is another popular stone because of its turquoise color, usually opaque. It is believed that Andean opal will lose its color when exposed to air, so the stone is often “fixed” with a glue-like coating.

Fire opal is usually transparent and lacks the color play of other opals. It ranges in color from yellow to orange to red, with red being the most desirable. Fire opals, unlike precious opal, is often faceted and less expensive.

Common, or “potch,” opals come in three basic varieties: Honey opal, which has no color play and is often used in bead form; prase opal, which is a pretty green color thanks to the presence of nickel and has a cloudy look similar to that of chrysoprase; and seascape opal, which is a blue-green color, often with dendritic inclusions.

In medieval times, the opal was thought to bring great luck, possessing all the virtues of the various gemstones, thanks to the color play. It was believed that if you wrapped an opal stone in a fresh bay leaf, it could make you invisible. However, in Victorian times, the 1829 novel “Anne of Geierstein,” by Sir Walter Scott made the opal disreputable, described as a talisman that turned to colorless stone when touched by holy water—an event that killed the wearer. After his novel was published, the opal was believed to be a symbol of bad luck and death, and sales in Europe diminished.

Even in the early 20th century, fear and suspicion of the stone lingered, particularly with Russians, who thought the stone embodied the evil eye. That is perhaps why the opal appears in so few of the great jewelry collections of the 20th century.

The rebellious Art Nouveau artisans, though, rejected Victorian conventions and embraced the “organic” look of opal cabochons, which worked well with their insect motifs and elaborate enamel work.

Opals, being soft and subdued, are nearly the opposite of diamonds, with their hardness, brilliance, and fire. Yet these two stones complement each other well, particularly when a large opal cabochon is set within a protective ring of small, faceted diamonds.

Cartier made two pearl necklaces for Barbara Hutton featuring such opal-and-diamond clasps. One featured two rows of golden cultured pearls, and she would often wear this necklace with her beloved ruby and diamond tiara. The other was used on a strand of pearls once worn by Marie Antoinette and given to Hutton in 1933 by her father on the occasion of her marriage to Prince Alexis Mdivani.

Synthetic composite opals come in two forms: doublets and triplets. Doublets have an outer layer of precious opal, but a base of potch opal, whereas a triplet has a base of common opal, a thin layer of precious opal, and a protective covering of rock crystal. These composites can be identified by looking at them side-on with a magnifying glass.

In 1973, Gilson, the French company that developed imitation turquoise, also created imitation opal in the lab with nice iridescence but clearly fake color patterning. In the United States, John Slocum made a tough glass that resembled opal, but it lacked the texture of opal and looked crumpled under magnification. The cheapest fake opal around is made of polystryrene latex, which has a milky bluish sheen.

The most important factor in determining the quality of a piece of opal is the brightness and evenness of color. To check, turn the stone 360 degrees and make sure the iridescent color appears all across the surface, with no “dead” zones. For what it’s worth, “opalescence” is an incorrect term to apply to an opal; it refers to the the bluish-white shimmer, or “shiller,” on other gemstones, such as the moonstone.

Opals that have been drilled are more prone to dehydration, but it is possible to restore a dried-out opal by submerging it in water. Some evaporation is inevitable over time, but you can slow it by storing your opals in moist cotton balls. Opals are particular sensitive to perfume, soaps, and detergents, so opal necklaces and rings should be removed when washing or grooming.

About our sources | Got something to add?

▼ Expand to read the full article ▼

Best of the Web (“Hall of Fame”)

All About Jewels Dictionary

All About Jewels Dictionary

This incredible reference dictionary on jewelry, from Enchantedlearning.com, is both beautiful and comprehensive. S… [read review or visit site]

Morning Glory Antiques and Jewelry

Morning Glory Antiques and Jewelry

Jewelry collectors, feast your eyes on this internet gem! It's a goldmine of jewelry information featuring all styl… [read review or visit site]

Cathy Gordon's Jewelry Gallery

Cathy Gordon's Jewelry Gallery

With its vast galleries featuring clear images of jewelry and style, this site really covers it all! Divided up by … [read review or visit site]

Jewel History

Jewel History

Since March of 2007, readers of Lori Ettlinger Gross’s Jewel History blog have been treated to her weekly (someti… [read review or visit site]



Clubs & Associations

Other Great Reference Sites

Most watched eBay auctions    

Huge Natural Opal Diamond Snake 1920s 14k Gold Art Deco Antique Ring 8.759ct/ 9k Rose Gold Solid Black Opal Ring, 375Vintage Modernist Gold Faced Solid Silver Opal Amethyst & Moonstone PendantAntique Vintage Nouveau 10k Gold Australian Fire Opal Pink Sapphire Ring Sz 7Early Clogau Rose And Yellow 9ct Gold Celtic Opal Ring9k Gold 9ct Gold Vintage Opal Celtic Design Ring Size O18ct/ 18k Gold Large Pear Drop Fiery Opal & Peridot Large Pendant, 7509k Gold 9ct Gold Vintage Design Opal Ring Size OVintage Natural Australian Opal Cluster 14k Gold Cocktail Ring~beautiful FireVtg 10k Gold Marquise Cut Firey Australian Opal October Birthstone Ring Size 6Vintage Native Navajo Pawn 14k Gold Sessin Sugilite Sapphire Opal Earrings!9k Gold 9ct Gold Art Deco Opal Stunning Vintage Ring Size K9k Gold 9ct Solid Gold Vintage Design Opal Eternity Ring Size M14k Rose Gold Opal Size 7 Solitaire Never Worn Vintage Look RingEstate 8.38ct Amethyst Opal 9k Gold Cocktail Ring 7.7grams NrAntique Vintage C. 1900 Nouveau 14k Gold Australian Fire Opal Necklace PendantTiffany & Co Platinum Opal Diamond Ring Boxed Vintage Australian Huge 13.30 Cts!Mignon Faget 925 Sterling Silver Natural Opal Gemstone Designer Cuff Bracelet Antique Vintage Nouveau 14k Gold Tourmaline Opal Turquoise Shield Pendant!Victorian Romantic Revival 14k Gold .40 Carat Diamond Opal Flower Ring Size 8.514k Gold Opal Diamond Vintage Heart Shape Shooting Star Ring9ct/ 9k Whte Gold 10 Carat Opal Art Deco Ring, 37514k Diamond Black Opal Solid Vintage Pendant Necklace Boxed Rare Huge 14.85 Cts!14ct/ 14k Gold Opal Large Art Nouveau Design Cluster Ring, 585Estate Australian Opal Solitaire Ring Rose Gold Fine Natural Great MountingAntique Gold And Moonstone And Opal Insect Brooch9ct/ 9k Rose Gold Solid Black Opal Pendant Necklace, 375**estate 14k Yellow Gold Black Opal Pendant 3.1 Grams 10.5x17mm 14ct/ 14k Gold Fiery Opal Cluster Art Deco Design Ring, 585Art Nouveau 14k Yellow Gold Fiery Fire Opal Ruby Stone Snake Serpent Pendant$3500 Vintage 14k White Gold Oval Cut Opal & Diamond Ladies Ring 3.7g14ct/ 14k Rose Gold Diamond & Black Opal Art Deco Pendant, 585Estate Vintage 14k Gold Fire Opal Iridescence Ring 5 Gemstones Basket Setting Stunning Opal With Very Good Color Play And Diamond 14k Gold Ring - Size 5Vintage Opal 10k Gold 3 Stone Awesome Color Play Size 7 RingVintage 14k Gold Earrings Opal Gemstones Stud Pink Blue Rainbow-like IridescenceFantastic Antique 9ct 9k Rose Gold Opal Spider Brooch Pin Victorian NaturalisticBeautiful Vintage 9ct Rose Gold & Large Opal Ladies Ring 1975Estate 9k Yellow Gold 1.15 Ct Natural Oval Colorful Opal Solitaire RingAntique Vintage Nouveau 14k Gold .54 Ct Sapphire Princess Opal Harem Ring Sz 5.59ct Solid Gold Pearl & Opal Stick PinEstate 6.73ct Natural Ethiopian Opal And Diamond 14k Solid White Gold RingFine 18ct / 18k 750 Gold Art Deco Diamond And Opal PendantA Stunning Pair Of Oval 4.00 Cts Opal Solid 9ct Gold EarringsAntique Vintage C. 1900 Art Nouveau 14k Gold 3.78 C Australian Opal Ring! Sz 6.5Vintage 14k Yellow Gold Opal Topaz Brooch Pin Pendant Filigree Cross Not ScrapVintage Old Pawn Sterling Zuni Lapis & Opal Inlay Half Hoop Pierced EarringsFine Black Opal Doublet Diamond And Sapphire 9ct Gold Ring 9k 3759ct Scrap Gold Gate Bracelet Chain & Opal Ruby Pendant And RingWonderful Vintage 14k Wht Gold Black Opal & 3mm Pearl Stick Pin - 1.3grEstate 14k Gold Ruby & Opal Ring Size 7 No Reserve18k Gold 18ct Solid Gold Vintage Fiery Opal Trilogy Ring Size NVintage Opal Pear Cut Halo Cluster 14k Yellow Gold Ring Size 6.5 Excellent14k Gold Bracelet-opals-diamonds-12.2 Dwt-tiny Diamondvintage-nr!Vintage 10k Gold Opal Flower Ring Gemstone Signed Rainbow Iridescence 2.88 GrsEstate $1900 14k Yellow Gold 0.55 Ct Natural Orange Fire Opal And Diamond RingA Stunning Art Deco Design 9ct Gold Opal And Sapphire Five Stone RingAntique Design 13ct Aaaa+ Natural Opal 925 Sterling Silver Ring Size 9/r67030A Fine Art Deco Design 9ct Gold Opal And Sapphire Cluster RingLovely, Australian Opal Triplet- 5ct- Vintage Estate Find.