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 JewelHistory blog have been treated to her weekly (sometim… [read review or visit site]



Clubs & Associations

Other Great Reference Sites

Most watched eBay auctions    

Fine Heavy Victorian Enamel, Opal And Diamond 18ct Gold PendantVintage Designer Ver Lee 4.00ct Opal Cabochon 14k Gold Band Ring NrStunning Antique Art Deco 18ct Gold Free Form Boulder Black Opal RingEstate Black /blue 4.50ct Opal Onyx 14k Gold Oval Large Cufflinks 18.4 Grams NrFine Art Deco 2.1/2 Carat Black Opal Doublet 18ct Gold Ring.Estate Diamond 5.10ct Opal 18k Gold Drop Pendant 8.1 Grams NrAntique Victorian Silver Gilt Fly Bug Brooch, Opal, Garnet And Seed Pearls BoxedFine Edwardian Love Heart Opal Rose Gold Ring,1900Estate Emerald Opal 14k White Gold Flower Band Ring NrVtg Victorian Romantic Revival 14k Gold W/ Australian Opal Shield Brooch PendantVtg 10k Gold Large Black Opal Triplet Mid Century Modern Mcm Cocktail Ring Sz 6Estate Carved Face Moonstone Tourmaline Opal Gold Ring 10.7 Grams NrArt Deco 12.57ctw Natural Australian Opal Diamond Akoya Pearl 14k Gold PendantStunning Vintage 9ct Gold 5.0ct Precious White Opal RingFine Opal Gold Bug Ring.Finest Antique Art Deco 9ct Gold Black Opal Cabochon Pendant & ChainOpal Ring Vintage Art Deco 14k White Gold Filigree Fine Jewelry Size 6.25 Retro Victorian 14k Solid Gold Opals & Diamonds Ring,6 3/4Stunning Vintage 9ct Gold Precious White Opal Cabochon Marquise RingStunning Antique Vintage 3ctw Natural Opal 14k Yellow Gold Ladies RingVictorian Romantic Revival 14k Gold Diamond Green Firey Opal Enhancer Pendant NrVintage 14k Gold .15 Carat Tw Diamond & Oval Cut Firey Opal Stick Lapel Pin Nr***beautiful 18ct Gold Opal & Diamond Three Stone Ring Uk Size L***14k Solid Gold Top Quality Natural Solid Opal & Orange Sapphire Ring Sz 10.25Fine Pair Of Art Deco Design Opal 18ct Gold Drop EarringsAntique 1921 Bham Art Deco 9ct Rose Gold Opal Ring Size N+ (w33)Vintage Estate Natural 8.00ctw Solid Australian Opal Diamond 14k White Gold RingAustralian Opal & Diamond Ring Yellow Gold Estate Vintage Natural Cabochon CutVintage Natural 8.00ctw Solid Australian Opal And Diamond 14k White Gold RingVtg Studio Art 14k Gold Large Natural Pink Fire Opal Butterfly Brooch Pin Nr MrcStunning Vintage Cabochon Black Opal & 9ct Gold RingArt Deco 9 Ct / 9k Yellow Gold Opal Tear Drop / Dangling EarringsQuality Vintage 9 Ct Gold Opal Emerald RingFinest Vintage 9ct Gold Precious White Opal Cross Pendant Vintage 1.00ctw Fiery Opal & White Topaz 10k Yellow Gold Stud/dangle EarringsOnyx Opal Jade Ruby Coral 14k Gold Chinese Dragon Large Pendant 14.9 Grams NrHeavy Vintage 14k Yellow Gold 10mm X 12.5mm Opal Cluster Cocktail Ring Size 4.25Old Pawn Vintage Ss Opal Chip Bracelet Cuff Navajo Jewelry Signed Livingston 58g14k Solid Gold Top Quality Vintage Natural Solid Opal & Diamond Ring Sz 6.75Vtg Mid Century 14k Gold Large Firey Mexican Opal Ladies Cocktail Ring Size 9 NrArt Deco Vintage 2.00ctw Australian Opal Dangle Drop 14k Gold EarringsAntique 1802 Vermeil 10.0ct Opal/pearl Mourning Brooch W/ Black Mesh Bow/ribbon1 Ct Australian Opal & Diamond Ring 14k Yellow Gold Natural Heart Cabochon Cut14k Solid White Gold Top Quality Natural Solid Opal & Diamond Pendant AmazingVtg Gilbert Nelson Navajo Opal Black Onyx Sterling Silver Pendant Flush InlayFine Victorian Opal, Ruby And Diamond Gold Ring.Fine Vintage Garnet And Opal Cluster Gold Ring+ Vintage Native American Navajo Designer Carlos Opal Rope Cuff BraceletStunning Ladies Vintage 12 Opal Cocktail Ring In 14k Yellow Gold Circa 1960's14k Gold Oval Cut Australian Opal & Channel Set Diamond Ladies Ring Size 7 NrVintage Navajo Robert Brown Sterling Silver Lapis & Opal Watch Bands | G TBeautiful Big 9ct Gold And White Gold Art Deco Opal Diamond Cluster RingStunning Vintage 9ct Gold Orange Fire Opal Pear Cut RingJay King Dtr Sterling Silver Vintage Antique Finish Fire Opal Earrings 7gDolphin Opal Pendant 14k Yellow Gold Estate 1.60 Inch Width No ReserveFine Vintage Black Opal Doublet Gold Ring.9k Carat Yellow Gold Pendant Opal & 1pt Diamond 14k 18" Chain Necklace Vintage Vintage Estate Kabana 14k Yellow Gold Opal Ring Size Us-7/t54/uk-oAntique 14k Gold Opal & Multi-color Gemstone Crown BroochVintage 14k Gold 1.50ct Cabochon Opal Cluster Filigree Designer Bar Brooch