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Lightning Trapped: A Guide to Opals

There is in them a softer fire than the ruby, there is the brilliant purple of the amethyst, and the sea green of the emerald - all shining together in incredible union. Some by their splendor rival the colors of the painters, others the flame of burning sulphur or of fire quickened by oil.

-Pliny the Elder


In his landmark 1st Century AD encyclopedic work, Natural History, Roman author, naturalist, and philosopher Pliny the Elder describes the opal's ability to fascinate and mesmerize. The finest opals, it was believed, were imbued with the best qualities of all the other gemstones. They seem to be lit from within, and they flash rainbow hues in kaleidoscope patterns. This “play of color” is the opal's calling card and ensures that no two opals are exactly alike.


These unique gems are some of the oldest, most coveted, diverse precious stones in history, and many of them come with interesting stories attached. You might have previously admired vintage opal gemstone necklaces or antique opal rings, but do you know where the opal stones originated? Learn more about this precious gem and the science and legends behind them with this guide to opals.



A necklace featuring a 20.56 carat black opal

A necklace featuring a 20.56 carat black opal

Origins and Formation


Opals are a mineral composed primarily of silicon and oxygen with water. Water can account for about 3-20% of the opal's weight, but, on average, it is around 10%. Over millions of years, water from seasonal rains in dry regions such as the Australian Outback dissolves chemical ingredients in desert sand, carrying silica (a silicon and oxygen compound) down into the cracks of underground rock. When these silica deposits harden, an opal gemstone is formed. Don't let the relatively simple explanation fool you - the solidification process of this precious gem occurs at a rate of only about 1 inch per 20 million years. Before it is even unearthed, an opal boasts a fascinating history!

This chocolate opal specimen from Ethiopia displays a full rainbow of color.

This chocolate opal specimen from Ethiopia displays a full rainbow of color.


Compared with other precious gems, opal is unique in its ability to diffract light, resulting in the stone's distinctive “play of color.” According to the Gemological Institute of America, the scientific explanation for this phenomenon was discovered in the 1960s by Australian scientists. Under a electron microscope, they saw that spheres of silica gel were stacked in a grid-like pattern. These spheres caused interference, refraction and diffraction of light, the result of which was the opal's distinctive color play. As light waves pass through the opal, they bend around the tiny particles of hydrated silica, as well as bits of silicon and oxygen suspended within the stone, then break up into the entire spectrum of colors. A kaleidoscope of colors is the result.


Although opal deposits have been found all over the world (including in Brazil, Ethiopia, Guatemala, Honduras, Indonesia, Japan, Mexico, Russia and even in the United States), most fine opal hails from Australia. In fact, upwards of 95% of opals come from the land down under, with the majority being white opal from the fields of Coober Pedy in the southern part of the continent. Other famous deposits have been discovered in New South Wales, especially those at Lightning Ridge and White Cliffs. The country produces so much opal that it was officially adopted as the national stone of Australia.



A black opal from the Lightning Ridge region of Australia.

A black opal from the Lightning Ridge region of Australia.




Types of Opal


Opals come in dozens of varieties and nearly every color of the rainbow. While these gems can be transparent, translucent or opaque, almost all of them display the opal's signature play of color. In the realm of fine jewelry, the most coveted gemstones include the following:



    • White Opal - The most common opal type, this stone has a translucent to opaque white or light gray base with play of color.
    • Black Opal - The rarest and costliest of all the opal types, this gem should display a translucent to opaque base of black or some other dark color with play of color.
    • Crystal Opal - Transparent on a colorless to dark gray base with play of color
    • Fire Opal - These opals are quite unique compared to their cousins. The fire opal may or may not show play of color, but is instead coveted for their red, orange or yellow bases that are transparent to translucent (rather than opaque). They achieve this color thanks to the presence of iron during their formation. Fire opals are often faceted, setting them apart from the standard cabochon cut of most opals that enhances color play. The best examples of fire opals are found in the state of Querétaro, Mexico.

This fire opal and diamond ring exhibits some play-of-color.

This fire opal and diamond ring exhibits some play-of-color.



History and Lore


Pinning down the origin of the word opal is difficult, but it likely comes from the Sanskrit upala, meaning precious stone or jewel. The word itself is adapted from the Latin term opalus, and there is debate that this might have come from the Ancient Greek, opallios, meaning “to see a change in color.” It also could have been adapted from the wife of Saturn and goddess of fertility in Roman mythology, Ops.


There is archaeological evidence of opal gem mining from more than 10,000 years ago, but the gemstone really began its rise in popularity in the Western world during the Roman Empire. The stones were thought to be worthy of the gods and, therefore, imbued with supernatural powers. They were presented to the gods as offerings, soldiers would carry them for protection, and men would give them to their wives to enhance desire or faithfulness. One legend even tells the story of a Roman Emperor trading one-third of his kingdom for a single opal.


The ancient Greeks also treasured the opal, and the poet Onomacritus penned a poem dubbing it “the gem of cupid.” They believed opals had to power to grant prophecy and protect from harm and disease.


Arabic legends liken opal to flashes of lightning. The Bedouins of the Sahara believed the opals fell from the heavens during storms and had lightning trapped inside of them. Around 290 B.C., the Romans were calling it ceraunium, which comes from the Bedouins meaning “thunderstone.”


Opals also have a mysterious side, and at certain points in history have been regarded as bad luck or even cursed objects. This reputation likely began with the novel Anne of Geierstein written by Sir Walter Scott in 1829. In it, a Baroness wears an opal with magical powers in her hair. When the opal gem comes in contact with a drop of holy water, it turned dark and the Baroness dies with both her and the gem reduced to only ash.


Opal is the October birthstone, and some even consider it bad luck for anyone born outside of that month to wear it. It was also once believed to be a charm able to preserve the color of blonde hair.


Opal is the October birthstone, and some even consider it bad luck for anyone born outside of that month to wear it. It was also once believed to be a charm able to preserve the color of blonde hair.


Famous Opals



An antique Edwardian opal and diamond pendant.

An antique Edwardian opal and diamond pendant.



Opals have held a fascination with emperors and royalty for centuries. In Ancient Rome, Mark Antony was said to have loved opals and gave them as gifts to his lover, Cleopatra. According to Pliny the Elder, Antony coveted an opal belonging to Senator Nonius and offered to purchase it for 2,000,000 sesterces, which was much more money than it was worth. For reference, 1,000 sesterces could pay a year's salary for a soldier. Nonius refused to sell, and Antony gave him an ultimatum - sell or be banished. Nonius chose banishment, leaving his wife and family behind, but keeping his precious opal.


Opals were Queen Victoria's favorite precious stone, and she presented them to her five daughters on their weddings days. At the time, the Royal Court was considered the height of fashion, so with the Queen and her daughters wearing opal, they were in high demand.


Andy Warhol was a huge fan of opals and became an avid collector. He even devoted a photography project to the stone entitled “Opal: the Rainbow Gem,” where he depicted them through the lens of a microscope.


Below are a few especially notable examples of opals:


The Burning of Troy

This was a 700-carat black opal with dramatic red flashes given by Napoléon to his beloved Empress Joséphine. After her death, the stone disappeared and was not seen for a century. It then turned up quite mysteriously in Vienna, and is now owned by the city government. It was valued by the city so highly that even after the economic devastation of World War I, they refused to sell it. It disappeared again after World War II and has yet to resurface.


The Flame Queen Opal

Often regarded as the most famous opal in the world, it weighs over 52 grams and is exceptionally beautiful. It has the appearance of an eye with a central section that can appear either golden or red, surrounded by a ring of deep blue-green. Discovered in the Lightning Ridge region of Australia in 1914 at 35 feet underground, it was an extraordinary find. John D. Rockefeller purchased it in 1949 for $75,000 - the equivalent of $1.4 million today.


The Queen's Opal

Also known as the Andamooka Opal, this stone was discovered in an opal mining town in South Australia called Andamooka and weighs 40.6 grams. Queen Elizabeth II was gifted this precious opal in 1954 during her first visit to Australia, and it was later set into a palladium necklace with diamonds.


The Pride of Australia

Appropriately named for its shape resembling the continent itself, it was discovered in 1915 and has blue and black veins with red streaks. It was stolen from the Forest Lawn Museum in 1961 and never recovered.


Caring for Your Opal Jewelry



A beautiful black opal and diamond jewelry suite.

A beautiful black opal and diamond jewelry suite.



Opals are some of the softest, and therefore most delicate precious stones around, and they require gentle wear and care. They rank at a 5.5 to 6.5 on the Mohs scale, which is a scale of hardness and scratch resistance used in classifying minerals. In comparison to an emerald at 7.5 or a diamond at 10, a natural opal is far softer than the average gemstone.


In fact, ordinary dust is largely made up of quartz, which ranks at a 7 on the Mohs scale. This means that simply wiping dust off an opal stone can reduce its polish over time. To prevent this, use a soft cloth to wipe your opal jewelry and mild soap if necessary; never use harsh chemical cleaners or steamers.


The Mohs scale is also an indication of the wearability of a gemstone. As already discussed, because opals are soft they can scratch or ding easily. This makes them less popular for rings and better suited for earrings, pendants or brooches. However, wearing opal rings only on occasion or removing them before engaging in vigorous physical activity can extend the life and luster of the stone.


Finally, opals are high in water content (up to 20%), putting them in danger of drying out and cracking if not taken care of properly. If an opal stone dries out, it is prone to cracking and losing its play of color. This can be combated by storing them wrapped in soft, damp cotton. You want to make sure you do not keep opals in a dehumidified space or near sources of heat or cold.


With proper care, your opals can maintain their delicate play of color and extraordinary brilliance for generations. Would you like to add a piece of opal jewelry to your collection? You can Browse M.S. Rau's collection of fine opal jewelry and opal rings for women.


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