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    

18ct/ 18k Gold Huge Opal Antique Ring, 750Fine Art Deco Opal And Diamond 18ct Gold Double Cluster Ring 18k 750Gia 11.52 Ct Natural Ethiopian Opal Diamond 14k White Gold Estate Cocktail Ring9ct/ 9k Gold Victorian Style Opal Ring, 375Antique Victorian 15ct Yellow Gold Fiery Opal Diamond Ruby Fly Bee Pendant A/fAntique Victorian 10k Gold Gf Opal & Pearl Slide Chain Necklace & Bonus Locket15ct/ 15k Gold Sapphire,seed Pearl, Ruby & Opal Victorian Butterfly Clip BroochVintage 14k Gold Amazing Elegant 14.64ctw Diamond & 22.5 X 14.3mm Opal PendantFine Opal Emerald Cluster 9ct Gold Ring 9k 375Huge 15ct Freeform Natural Australian Opal Vintage 14k Gold 1960s PendantEstate 10.50ctw Natural Opal And Diamond Ring In 14k Yellow Gold Antique 9ct Gold Pendant Set With Natural Large Black Opal Diamond 15.92ct Opal 18k Yellow Gold Drop Pendant Necklace 13.2 Grams NrVintage Black Opal 14k Gold Diamond 1.28 Tcw Approx Tennis BraceletVintage Estate Natural Untreated 1.50ctw Fire Opal And Diamond 14k Gold PendantCertified Estate Stunner 2.8 Ct Rare Natural Mexican Fire Opal Diamond 14k Ring!Estate $1600 14k Yellow Gold 0.70 Ct Natural Black Opal And Diamond Ring Vintage 14k Gold Beautiful 20 X 12mm Oval Opal Solitaire Cocktail Ring Size 6.25Victorian Design Ladies Opal & 9ct Gold Cluster Ring F0817Fine Vintage 14k Solid Gold Opal Pierced Stud Earrings9ct/9k Fine Vicorian Style Opal Type Rose Gold Ring 375Vintage Antique 1930's 9ct Art Deco Venetian Opal Opalescent Glass Bead NecklaceEstate 6.94ctw Natural Opal And Diamond Ring In 14k White Gold **antique Platinum Opal Ring 17x11.7mm Size 8.25 2.4 GramsVintage Natural Opal Cornflower Blue Topaz 14k Gold Teardrop Dangle EarringsAntique Victorian 10k Rose Gold Diamond & 4 Opal Stone Ring Gorgoeus Look $9.9914k Solid Black Opal Ring Vintage Australian Victorian Box Huge 15.45 Carats!Antique 1930s $10,000 7ct Natural Black Opal Emerald Platinum RingAntique 1920s Art Deco 1.25ct Opal Old Mine Cut Diamond 14k Gold Platinum RingBeautiful 9ct Gold 3.00 Carat Oval Opal Decorate Pendant & Chain Beautiful Vintage 14k Gold Opal Dangle Earrings56.4ct Natural Ethiopian Black Opal Play Of Color Facet Rough Specimen Yzo405718ct/ 18k Gold Diamond & Opal Victorian Style Ring, 750Estate $2900 14k Yellow Gold Natural Colorful Opal And Synthetic Sapphire RingEstate Australian Opal & Diamond Ring 14k Yellow Gold Natural Cabochon VintageEstate 5.502ctw Natural Opal And Diamond Ring In 14k Yellow Gold Estate Natural 3.05ctw Australian Opal & Diamond 14k Gold Drop Pendant NecklaceEstate 7.68ct Natural Ethiopian Opal And Diamond 14k Solid Rose Gold Ring4 Ct Tanzanite & Australian Opal Earrings Yellow Gold Round & Cabochon CutVintage Antique 1930's Art Deco Opal Peacock Venetian Foil Bead Drop NecklaceAustralian Opal Estate Brooch 14k Yellow Gold High Detail Finish Fine Vintage9ct/9k Gold Opal And White Paste Stone Pendant And Chain 375Antique Art Deco Large Black Opal Diamond Floral 14k Gold Ring Estate 4.23ctw Natural Mexican Fire Opal And Diamond Ring In 14k White Gold A Stunning Vintage Large Opal & 9ct Gold Cluster RingEstate 4.40ct Natural Opal And Diamond Ring In14k Yellow GoldAntique Victorian 10kt Gold Seed Pearls & Opal Fleur De Lis Cross Pendant 2gramsVintage 14k White Gold Natural Opal Filigree Ring - Size 7.251 Ct Australian Opal Pendant 14k Yellow Gold Natural Cabochon Cut EstateEstate $1700 14k Yellow Gold 1.50 Ct Natural Colorful Opal And Sapphire RingVintage Natural White Opal Oval Cabochon 14k Yellow Gold Cluster PendantVintage Designer Sterling 925 Silver Blue Topaz Opal Diamond Estate Ring! Sz 6.5Estate 6.12ctw Natural Mexican Fire Opal And Diamond Ring In 14k White Gold 14k Gold Antique Ob Solitaire Ring By Ostby BartonVintage 14k Gold Opal & Diamond Pierced EarringsA Beautiful Dainty Pair Of Oval Opal Earrings In 9ct Gold Rope Design MountsVintage European Hallmarked 18k Gold 23mm X 12.5mm Doublet Opal Cocktail RingEstate 4.10ctw Natural Mexican Fire Opal And Diamond Ring In 14k White Gold Fantastic Antique Edwardian Real Opal Beads Faceted Crystal Necklace Beautiful56.65ct Natural Ethiopian Black Opal Play Of Color Facet Rough Specimen Yzo4047