The Roman senator Nonius owned a hazelnut-sized opal so beautiful that Mark Antony coveted it for Cleopatra. Nonius refused to part with it. He chose exile and the loss of his entire fortune over surrendering the stone—or so Pliny the Elder recorded in his *Natural History*. Eighteen centuries later, that same stone was ruined by a single novel, only to be saved by a queen. October has two birthstones—opal and tourmaline—and no other month has been assigned such a contrasting pair: one stone with a turbulent history, and another that, for most of its existence, didn't even have a name.
Opal: Light Captured in Water
Opal is not a crystal. It is a hydrated silica—containing anywhere from a few to over a dozen percent water by weight—structured as microscopic spheres. If these spheres are uniform in size and arranged in orderly rows, they diffract light like a diffraction grating, causing the stone to shimmer with colors that shift with every movement. This phenomenon is known as "play-of-color," and for a long time, it remained a mystery. It was not until the 1960s that Australian researchers, using electron microscopy, revealed the internal structure of opal and explained the source of its radiance.
All of opal’s virtues and flaws stem from this unique structure. One advantage is that no other stone displays such a multitude of colors simultaneously; the Romans believed that opal embodied the qualities of all other gemstones because it possessed the hues of each one.
One drawback is its softness: opal has a hardness of 5.5–6.5 on the Mohs scale—lower than that of quartz, the main component of ordinary dust. Furthermore, because it contains water, it reacts poorly to high temperatures and rapid drying, which can cause a fine network of cracks to form.
About ninety percent of the world's supply comes from Australia. Coober Pedy produces white and crystal opals, while the world's most valuable black opals—characterized by a play-of-color against a dark background—come from Lightning Ridge in New South Wales. Since 2008, Ethiopia has also become a significant source; however, opals from the Wollo region have a specific trait one should know before buying: they are porous and absorb water, causing them to lose their transparency and play-of-color for several hours after getting wet. They regain their original appearance once dry, though not every owner is aware of this.
How a single novel tarnished the stone's reputation
Throughout antiquity and the Middle Ages, the opal was considered a stone of good fortune. It was believed to bring hope, purity, and protection; it was thought to strengthen eyesight and—when worn by blondes—prevent their hair from darkening. A single literary event changed this perception. In 1829, Walter Scott published the novel *Anne of Geierstein*, in which the mysterious Lady Hermione wears an opal in her hair that reacts to her moods. When a drop of holy water falls on the stone, the opal loses its luster, and its owner dies the following day.
The novel was a bestseller, and that was all it took. Within a year, opal sales in Europe plummeted by half, and the belief that the stone brought bad luck persisted for fifty years—even though, in Scott’s story, the stone brings misfortune to no one but simply shares in the heroine’s fate. The tide only turned thanks to Queen Victoria, who loved opals, gave them to her daughters as wedding gifts, and wore them in public. When Australian deposits were discovered in the second half of the 19th century, the stone regained its popularity and has remained in favor ever since.
Tourmaline: A Stone of Many Names
The story of tourmaline was quite the opposite: no one was afraid to wear it, yet for centuries, no one even realized they were wearing it. Red tourmalines were mistaken for rubies, green ones for emeralds, and blue ones for sapphires. The name itself comes from the Sinhalese word *turamali*—meaning simply "stone of mixed colors"—under which Dutch merchants imported these multicolored stones from Ceylon in the early 18th century, unaware that they were all the same mineral. They did, however, discover a peculiar property: when heated, tourmaline attracts ash and dust particles. Consequently, they used the stones to clean their pipes and called them *aschentrekker*, or "ash-puller." Today, this phenomenon is known as pyroelectricity, and tourmaline serves as a textbook example of it.
Chemically, tourmaline is a complex borosilicate with a variable composition, and it is precisely this variability that gives rise to its colors. Pink and red tourmaline—known as rubellite—owes its hue to manganese; blue indicolite to iron; and green verdelite to iron and chromium. Bicolored tourmalines also exist; a crystal cross-section featuring a pink center and a green rim reveals why they are called "watermelon tourmalines." With a hardness of 7–7.5, tourmaline is significantly more durable than opal, making it perfectly suitable for everyday rings.
Throughout history, tourmaline has had two great admirers.
The first was the Empress Dowager Cixi, who ruled China in the late 19th century and purchased pink tourmalines from California’s Himalaya Mine in such vast quantities that, upon her death in 1908, the mine lost its primary buyer and soon closed. The second is the modern jewelry industry, which gained a new gemstone in 1989: copper-bearing tourmalines discovered in the Brazilian state of Paraíba, boasting a neon blue-green hue unlike that of any other mineral. Today, Paraíba tourmaline is one of the most expensive colored gemstones in the world, with a price per carat that can exceed that of sapphire.
Which stone to choose for October
Opal has appeared on the list of birthstones since 1912; tourmaline was later added as an alternative, and a 1952 revision specified pink tourmaline. In practice, the choice between them depends on how the jewelry will be worn.
Opal is a stone suited for earrings, pendants, brooches, and rings worn on special occasions. If worn daily on the finger, it requires a setting that protects its edges and an owner willing to remove it before gardening, using a sauna, or washing dishes in hot water. Many opals found in more affordable jewelry are doublets or triplets—thin slices of opal bonded to a dark backing and sometimes topped with a layer of quartz.
It is not a deception, provided it is disclosed, but it is worth asking.
Tourmaline comes with no such caveats. It withstands daily wear, is unaffected by water or cosmetics, and offers a wider range of colors than any other gemstone. The only thing to watch out for is ultrasonic cleaning, as tourmalines often contain internal fractures that vibrations could enlarge.
Opals and tourmalines at INKLUZ
At INKLUZ, we set natural Australian opals—including large stones with an intense play-of-color—as well as natural tourmalines in a full spectrum of hues, ranging from pink rubellites to greens and blues. We have dedicated a separate silver collection to tourmalines, while larger, certified stones are set in gold. You can view them all at inkluz.com and at INKLUZ boutiques located at 64 Mokotowska Street in Warsaw and 4 Szafirowa Street in Lublin; with opals, in particular, it is well worth seeing in person how the stone’s appearance shifts with every movement of the hand.
