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    

Antique Victorian 1880s Opal & Banded Agate Gold Torpedo EarringsCertified Estate Rare Stunner 4 Ct Natural Superb Fire Opal & Diamond 14k Ring!!Antique Victorian 10k Rose Gold Belcher Claw Set Opal Sz 7 Solitaire Ring9ct/ 9k Gold Opal Victorian Drop Earrings, 375Vintage 18ct Yellow Gold Earrings With Purple Opal Stone 1.46g - S80Antique Vintage Art Nouveau 14k Gold Black Australian Opal Estate Ring! Sz 6Antique Victorian 10k Rose Gold 5 Colorful Opal Ring Gorgeous A Star Mark Sz 9.5Fine 9ct / 9k 375 Gold And Opal Necklace 9ct/ 9k Gold Diamond & Opal Art Deco Design Drop Earrings, 375Antique Vintage Nouveau 14k Gold Australian Opal Princess Harem Estate Ring! S 6Vintage 14k Yellow Gold Opal Cocktail Ring No Reserve18ct/ 18k White Gold Diamond & Opal Art Deco Design Cluster Ring, 750Vintage 9k 9ct 375 Solid Gold & Opal Ring See Photo For Size 14k Black Opal Diamond Ring Vintage Australian Solid Antique Huge 11.30 Carats!Antique Opal 14k Gold Estate Ring10k White Gold Opal, Tourmaline & Diamond Pendant- Vintage Estate Find-1.3 GramsWomen's Vintage Estate Jewelry 14k Yellow Gold Opal Bracelet 15 Grams 6.25"Antique Vintage Retro Mid Century Deco 14k Gold Mosaic Opal Diamond Ring! Sz 6.5Vintage 18k Yellow Gold Opal RingVintage Low Karate Or Gold Filled Opal Cocktail RingVintage Natural 2.10ctw Australian Opal And Diamond Solid 14k Gold Drop Pendant9ct/ 9k Gold Diamond & Opal Type Stone Cluster Ring, 375Fine Vintage 14k Gold Opal Delicate Necklace Pendant & Chain**estate 10k Yellow Gold Opal Garnet Ring 4.6 Grams Size 8 17.3x16.6mm Vintage 10k Yellow Gold Green Tourmaline & Australian Opal Ring 2.6g Sz 5.5 NrRare Estate Antique 4.75ct Fiery Australian Opal Diamond 14k Gold Statement Ring**estate 14k Yellow Gold Opal Amethyst Ring 9x8 Mm 2.2 Grams Size 7Estate 1.57ct Rhodolite Garnet Cocktail Ring 14k Yellow Gold $2500 A411Vintage Elegant 14k Solid Yellow Gold Firery Opal Hanging Dangle Earrings9ct Gold 9k Gold Vintage London Hallmarked Natural Opal Cluster Ring Size OVintage Estate Natural 1.02ctw Australian Opal Diamond Oval Cut Stud EarringsVintage Sterling Silver Wkl Lightning Opal Carved Moon Face Celestial Brooch PinVintage Sterling Silver 925 & Boulder Opal Pendant Vintage 5.8ct Opal Peridot Diamond Cocktail Ring 14k Yellow Gold Size 6.5Estate 14k Large Black Opal And Diamond Drop Pendant176.55ct 100% Natural New Found Africa Black Opal Facet Rough Specimen Ywog1314k Gold Vintage Natural Opal Filigree Size 6 ¼ Ladies RingFine 18ct / 18k 750 Gold And Opal Pendant 9ct Gold 9k Gold Opal & Amethyst Hallmarked Vintage Ring Size K , Boxed Fine Art Deco Design 9ct Gold Fiery Opal Ring 9k 375Vintage 14k Solid Yellow Gold Fire Opal Earrings No ReserveBeautiful Pair Of 9 Ct Gold Large Opal Drop EarringsLarge Antique Jerusalem A Stanetzky Sterling Silver Filigree Matrix Opal BroochVintage Opalite Gold Fill Floating Opal Necklace Pendant Screw Back Earrings SetGorgeous Vintage Modernist Solid Sterling Silver Natural Opal Jewellery Ring Q 8Vintage Navajo Art Jewelry Reverse Inlay Turquoise Opal Spiny Oyster Necklace Nr*mint* Estate 14k Yellow Gold Natural Orange Mexican Fire Opal Ladies RingAntique Victorian 10k Gold Colorful Opal & Seed Pearl Ring $9.99Sterling Silver Vintage 925 Navajo Open Band Fire Opal Ring Sz 6 (4.5g) - 5464609ct/ 9k Gold 2.5ct Opal Art Deco Ring, 375Vtg Sterling Silver - Zuni Turquoise & Opal Mosaic Inlay 1" Belt Buckle -16g30.55ct New Found 100% Natural Africa Black Opal Facet Rough Specimen Uywo32Antique 5.5ct Opal Diamond 14k White Gold PendantVintage Navajo Art Jewelry Reverse Inlay Turquoise Opal Spiny Oyster Earrings NrNyjewel 10k Solid Gold Vintage Opal Band RingVintage Old Sterling Silver Fire Opal Marcastie Ring Size 5 1/2 Grandmas EstateAntique Ostby & Barton Ob 10k Gold Colorful Opal Ring Look $9.99Antique Art Nouveau / Jugendstil Silver, Opal & Seed Pearl BroochGrandmas Estate Beautiful Western Sterling Silver Opal RingVintage 14k Gold Opal Flower Pendant Charm