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    

Vintage Handmade 14k Gold & Blue-green Opal Filigree Ring, Size 7, NrAntique Victorian Gold Gf Diamond Slide Watch Chain Opal Photo Locket NecklaceAntique Art Deco 14 K White Gold Filigree Sugar Loaf Polished Cabochon Opal RingGia Estate 29.59 Ct Natural Ethiopian Black Opal Diamond 18k Yellow Gold Ring18k Opal Diamond Ring Vintage Huge Box Fine Antique Vs Fg Cocktail 9.05 Carats!Very Pretty Art Deco 18ct Gold Opal / Diamond Ring.wow.Vintage Estate Genuine Solid 2.00ctw Semi-black Australian Opal 14k Gold RingAntique 1920s Hallmark 9ct 9 Carat Rose Gold & Fiery Opal Slave Bangle BraceletFine Victorian Style Opal Gold Cluster RingFine Art Deco 18k Gold 3 Carat Opal & Diamond RingRetro Vintage 2.46cttw Opal G/vs Diamond Estate Ring Deco 14k White Gold Jewelry Victorian Ring - Natural Opal 5 Stone 18ct Ring Set With DiamondsAntique Victorian 15ct Gold Opal & Amethyst Ring Size MEstate Diamond 4.40ct Opal 14k Gold Cluster Ring 6.4 Grams NrAntique 18ct Gold Small Beautiful Crystal Opal BroochVintage Genuine 2.65ctw Solid Australian Opal And Diamond Halo 14k Gold Ring14k Opal Cultured Pearl Necklace Vintage Strand Box Fine Real Deco 21" Long 7mmCollection Of Six 9ct Gold Diamond Sapphire Opal Garnet & More Ladies PendantsVintage Designer 14.85ctw Natural Australian Opal Diamond 18k Gold Bracelet10k Gold Vintage Ruby & Opal Cluster Cocktail Ring Sz.72.50 Ct Vivid Opal Cocktail Ring 14k Yellow Gold Natural Faceted Oval CutEdwardian Colorful Estate 10k Opal Emerald Seed Pearl Ring Not Scrap Size6.25 NrRare Art Nouveau 9 Ct Pink Rose Gold Fire Opal Pendant Fine Art Deco Design Opal And Diamond Gold Cluster Ring1 Ct Australian Opal Ring 14k Yellow Gold Estate Vintage Natural Cabochon CutVintage Estate 2.12ctw Natural Australian Opal And Diamond 14k Gold RingVintage 14k White Gold Natural Solid Opal & Diamond Halo Ring 14k Solid Gold Antique Handcrafted Australian Black Opal Ring Sz 7.25 IncredibleStunning Dainty Opal Clip In Earrings Vintage 9ct GoldVintage 14k Gold .36ctw Cabochon Fiery Australian Opal Solitaire Stud EarringsBeautiful Antique 9ct Gold Precious White Boulder Opal Solitaire Ring Fine 1922 Art Deco Opal 5 Stone 18ct Gold RingVictorian 10k Gold 3 Opals Band Style Ring Size 7 1/2 Dainty Estate No ReserveBeautiful 9ct Yellow Gold Vintage Opal And Diamond Cluster Ring Size JA Fine Vintage 14ct Opal And Diamond Ring$1650 Antique Vintage 3.5ctw Marquise Cut Opal & Diamond 14k Yel Gold Ring 4.3gEstate 2.20ct Three Stone Opal Gold Ring Nr$5,900 Victorian 28.54ct Rose Cut Diamond & Aaa Genuine Opal Bangle Bracelet 29gArt Deco 9 Ct / 9k Yellow Gold Opal Tear Drop / Dangling Earrings Beautiful 14k Gold Mexican Fire Opal Ring Size 6 No ReserveFine Tourmaline,peridot & Orange Fire Opal? Gold RingVintage 18k Yg Opal & Diamond Ring - Size 6 1/4 Stunning!!!!$2,100 Antique 14k Y Gold 4ct Natural Rhodolite Garnet & 1ctw Opal Ring 5.6g14kt Large Black Opal Pendant / Pin Or BroachVintage 10k Yellow Gold Australian Opal & Garnet Ring 2.6g Sz 9 No ReserveVintage Art Deco Black Opal Ring Large Unique Bezel Set Sterling Silver FineStunning 9ct Gold Vintage Opal Ring Size OVintage Marked 14k Gold Carved Opal & Diamond Ring 9 Grams Size 6.5 W Sizer Nice14k Solid Gold Top Quality Handcrafted Modernist Australian Black Opal PendantVictorian...14k.....opal....seed Pearls Ring...no ReserveUnbelievable Certified Natural 3+ct Black Fire Opal & Diamond 14k Vintage Ring!1.50 Ct Fine Australian Opal & Diamond Ring 14k Yellow Gold Natural Cabochon Cut10k Solid Gold Vintage Black Hills Opal Ring Sz 5.25 Rare FindBeautiful Vintage Pair Of Oval Opal 9ct Gold EarringsRare Stunning 24 Large Fire Opal & Hallmarked Solid Gold BraceletLarge Vintage 9ct Gold Opal Ring London 1985 Uk Size P Usa 8 No Reserve$1,750 14k Yellow Gold 1.5ct Natural Oval Cut Opal & .50ctw Tanzanite Ring 3.3g~ Antique White Fire Opal Red Ruby & Diamond Bypass Crossover Gold 10k Ring 7.75Antique C. 1940 Deco 18k Yellow Gold Opal Ruby Emerald Sapphire Princess Ring!Beautiful Vtg 5 Opal Sterling Silver Hinged Bracelet! Pg436