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, 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    

Stunning Art Deco 7 Carat Black Opal & 1.40 Carat Diamond 18ct Gold Cluster RingVintage Estate Natural 8.30ctw Solid Australian Opal And Diamond 14k Gold RingAntique Retro 4.25ct Opal 18k Rose Gold Oval Solitaire Ring NrVintage Felger 3.15ctw Lightning Ridge Black Opal Diamond 14k Gold Cabochon RingRare Antique Georgian 18ct Gold Stunning Opal Cabochon Set Stick Pin Circa 1820Antique Victorian 10k Solid Gold Etruscan Revival Firey Opal Ring Size 8 Sbb NrVintage Designer 3.25ctw Australian Opal Diamond 18k Gold Large Halo EarringsGia Certified 76.57 Ct Ethiopian Black Opal Diamond 18k Gold Pendant NecklaceRare Antique Georgian Regency 22ct Solid Gold Opal Cabochon Ring Circa 1830'sEstate Tahitian Pearl Opal 14k Gold Flower Bangle Bracelet Nr14k Opal Diamond Ring Vintage Huge Box Fine Antique Vs Fg Cocktail 12.50 Carats!Antique Edwardian 14k Gold Opals & 3 X 15 Point Diamond Ring,4 1/4 SweetHeavy Vintage 18k Gold 13.38ctw Vs Diamond/emerald/australian Opal Flower BroochVintage Diamond 3.06ct Opal Onyx 14k Gold Rectangle Ring 10.5 Grams NrAntique Opal Ruby 14k Gold Fly Bee Brooch Pin NrAntique 1.80ct Opal 14k Gold Enamel Drop Dangle Earrings 6.5 Grams Nr14k Diamond Black Opal Ring Vintage Huge Solid Fine Antique Cocktail 8.60 CaratsFine Art Deco Design Opal & Diamond 14k Gold RingFine Art Deco 3 Carat Opal Silver Pendant Necklace18k Diamond Black Opal Solid Vintage Earrings Box Antique Huge 8.70 Carats!Beautiful Vintage Art Nouveau 9ct Gold Bug / Moth Pendant Set With Opal Stunning Pair Of Art Deco 5 Carat Opal Silver CufflinksEstate Opal 14k Gold Marquise Filigree Ring NrVivid Australian Opal Ring Yellow Gold Natural Estate Great Mounting Size 7.5Estate 21.72 Ct Vvs Mexican Fire Opal Diamond Vintage Cocktail Earrings 14k GoldVintage 1970's 10k Yellow Gold English Boulder Opal RingEstate 14k Yellow Gold Pink Sapphire Diamond & Natural Opal Earrings 14kt ThlEstate Vintage 14k Yellow Fine Gold Opal Flower Antique Earrings (h52)Art Deco 9 Ct / 9k Yellow Gold Opal Tear Drop / Dangling EarringsAntique Victorian 10k Gold Solid Firey 6 Carat Opal Screw Button Pin Brooch SnmEstate Vintage 10k Yellow Gold .50ctw Natural Princess Cut Opal Childs Earrings Rare Large 14k Gold Opal European Mine Cut Diamond Pendant Necklace 12.4 Gms53.8ct Natural Ethiopian Black Opal Play Of Color Facet Rough Specimen Yol19Exquisite Antique 'marquise Shaped' 15ct Gold Opal + Turquoise Gemstone Ring.Vintage 9ct Gold Opal Handmade Ring C.1940 Beautiful High QualityEstate 0.70ct Opal 14k Gold Bow Ring NrGorgeous 14k Yellow Gold Dangling Earrings With 3.00 Ctw Opal! #r4Fine Art Deco 18k Gold & Platinum Opal & Diamond RingVintage Antique Art Deco 30's 3 Row Opal Opalescent Venetian Glass Bead NecklaceVintage, Unique 14k Yellow Gold Ring With 0.52 Ctw Diamond And Opals! # R27Very Long** Antique Victorian 10k Rose Gold & Gf Opal Slide Watch Chain & FobAntique 14k Gold Fancy Elegant 3.0ct Opal Filigree Hook Dangle EarringsAntique Victorian 18 Carat Gold 18k Ring - Opal Stones - Scrap - Large 5.5 GramsAntique Victorian Ladys 14kt Yellow Gold Opal And Pearl Brooch Pin Or PendantVintage 12.00ct Opal 14k Gold Drop Dangle Pendant 7.2 Grams Nr28.35ct 100% Natural Australian Opal 14k Yellow Gold Necklace Col50Vintage 14k Yellow Gold Ring With 0.73 Ctw Opals! Size: 6.25! #l12Art Deco White Opal Marcasite Insect Brooch 925 Sterling Silver1 Ct Vivid Australian Opal & Diamond Ring 14k Yellow Gold Natural Cabochon CutAntique Estate Art Deco Opal Filigree Ring 14k White Gold 1.25cts Size 5 3/4Rolled Gold Spider Brooch Stick Pins Opal Etc Seed Pearl Bar BroachVintage 14k Yellow Gold With Carved Opal Ring9ct Gold Earrings, Set 1 1/2 Carat Marquise Cut Opals And Citrines.Heavy! Vintage 14k Yellow Gold Bangle With 0.52 Ctw Opal! Exceptional! # S1Great Antique Art Deco 10k Gold Ring With 5 Graduated OpalsBagley & Hotchkiss Solid Two Tone 18k Gold, Opal & Diamond Omega Slide PendantVintage Opal And Emerald Ring Stunningly Different 9 Ct GoldVintage Antique Victorian Opal Yellow Gold Cocktail / Fashion RingVictorian/ Edwardian 10k Rose Gold Opal And Garnet Ring, Moore & Son, 4 1/2100 Ct Opal Necklace 14k Yellow Gold Clasp Natural Bead 9.5 Mm 21 Inch Long