October is unique in the gemological calendar, offering not one, but two distinct and spectacular birthstones: opal and tourmaline. While opal has long been the traditional emblem of the month, tourmaline has been added as a modern counterpart, providing a kaleidoscope of options for those born in this autumnal month. These gemstones are united by their extraordinary color, yet they are fundamentally different in their chemical composition, physical properties, and the visual phenomena they exhibit. Opal is celebrated for its mesmerizing play-of-color, a shifting iridescence that seems to contain fire and light, while tourmaline is renowned as the "Rainbow Gemstone," occurring in every color of the spectrum and often within a single crystal. Together, they symbolize hope, creativity, and emotional balance, offering a rich narrative of geological wonder, historical lore, and enduring beauty. This article will explore the history, origins, gemological properties, and cultural significance of both opal and tourmaline, providing a comprehensive guide to October's captivating birthstones.
History and Lore of Opal
The history of opal is steeped in myth and reverence, tracing back to antiquity. The very name of this traditional October birthstone is believed to have originated in India, the source of the first opals brought to the Western world. In Sanskrit, it was called upala, meaning "precious stone." This term was later adopted by the Romans, who called it opalus. The Romans held opal in the highest regard, considering it the "queen of gems" because it contained the colors of all other gems. A first-century Roman writer, Pliny the Elder, described opal as "a gemstone which combines the fiery red of the carbuncle (garnet), the brilliant purple of the amethyst, and the sea-green of the emerald, all shining together in a single stone."
Ancient beliefs surrounding opal were powerful and varied. Bedouins believed that opal held lightning and fell from the sky during thunderstorms. The ancient Greeks thought opals bestowed the gift of prophecy and provided protection from disease. For centuries, Europeans maintained that opal was a symbol of purity, hope, and truth. It was believed to embody the virtues and powers of all colored stones. However, opal's reputation suffered a significant blow following the publication of Sir Walter Scott's 1829 novel, Anne of Geierstein. The novel featured a cursed opal, and its immense popularity led to a sharp decline in the opal market, as the public associated the gem with misfortune. It took decades for opal to recover its standing as a beloved gemstone.
In contrast, the history of tourmaline is more modern, though no less colorful. The name tourmaline comes from the Sinhalese word turmali, meaning "mixed colored stones," which accurately reflects its incredible diversity of hues. For centuries, tourmaline was often mistaken for other gemstones, such as emeralds, rubies, and sapphires, due to its wide color range. Spanish conquistadors in the 16th century discovered green tourmaline in Brazil and initially confused it with emeralds. It wasn't until the late 19th century that tourmaline was recognized as a distinct mineral species. A pivotal moment in tourmaline's history occurred in the late 1800s when Chinese Empress Dowager Tzu-Hsi developed a profound passion for pink tourmaline. She purchased nearly the entire production from a California mine, establishing a significant market for the pink variety that continues to this day.
Geological Formation and Sources
The formation of opal and tourmaline could not be more different, reflecting their unique chemical structures. Opal is not a crystalline mineral but a "mineraloid," an amorphous solid composed of silica (silicon dioxide). It forms when water carrying dissolved silica seeps into cracks and voids within rocks, such as limestone. Over millions of years, as the water evaporates, the silica is deposited in microscopic spheres. It is the arrangement and size of these spheres that create opal's signature play-of-color, a phenomenon where light is diffracted as it passes through the structure. The most significant source of opal in the world is Australia, which produces the vast majority of the world's supply. Other important sources include Ethiopia, Mexico, and Brazil. Ethiopian opal, particularly from the Welo province, has gained prominence for its vibrant play-of-color and is sometimes found in a "precious" form that does not require treatment to be stable. Mexican opal is often found in a "fire opal" variety, which is prized for its intense body color, ranging from yellow to orange and red, and may or may not exhibit play-of-color.
Tourmaline, on the other hand, is a complex crystalline borosilicate mineral. Its intricate chemical formula allows for the substitution of various elements (such as iron, manganese, lithium, and aluminum) within its crystal lattice, which is responsible for its vast spectrum of colors. Tourmaline forms in pegmatites—coarse-grained igneous rocks—as molten rock cools and crystallizes. This process allows for the growth of large, well-formed crystals. The gemstone is mined in numerous locations across the globe. Brazil is a leading producer, yielding a wide array of colors. Other significant sources include Afghanistan, Pakistan, Sri Lanka, and Nigeria. The United States, particularly California and Maine, also has a history of tourmaline production, with Maine known for its fine pink and green varieties and California for its pink and bi-colored tourmalines.
Gemological Properties
Understanding the gemological properties of October's birthstones is crucial for appreciating their value and durability. While both are celebrated for their color, their physical characteristics differ significantly.
Opal Properties
Opal's value is primarily determined by its play-of-color, body color, and pattern. The most prized opals display a vibrant, multi-colored play-of-color against a dark or black body color (Black Opal), though white and crystal opals are also highly valued. The gem's hardness on the Mohs scale is relatively low, ranging from 5.5 to 6.5. This makes opal a softer gemstone that requires careful handling to avoid scratches and impacts. A critical characteristic of opal is its water content, which can be as high as 21%. This high water content makes certain types of opal, particularly those from Australia, susceptible to "crazing" (cracking) if they dry out too quickly. Ethiopian hydrophane opals are also known to absorb water, which can temporarily alter their appearance. Opal has no cleavage, meaning it does not have natural planes of weakness along which it might split, but it has a conchoidal fracture, meaning it breaks in a smooth, curved pattern like glass.
Tourmaline Properties
Tourmaline is significantly more durable than opal, making it a more practical choice for everyday jewelry, especially rings. It rates between 7 and 7.5 on the Mohs scale of hardness, providing excellent resistance to scratching. Tourmaline has no cleavage, which reduces the risk of breakage along internal planes, though it can be brittle and may fracture if subjected to hard blows. One of the most distinctive features of tourmaline is its ability to become electrically charged when heated or put under pressure—a property known as pyroelectricity and piezoelectricity. This characteristic was known to Dutch traders in the 18th century, who used tourmaline to pull ash from their pipes.
The color varieties of tourmaline are vast and are often given their own trade names. Pink and red tourmaline are known as rubellite. Blue tourmaline is known as indicolite. The most famous is probably the bi-colored or tri-colored variety known as watermelon tourmaline, which features a pink center and a green "rind." Paraíba tourmaline, a neon-blue to green variety from Brazil, is one of the most valuable and sought-after gems in the world due to its intense color caused by trace amounts of copper.
| Property | Opal | Tourmaline |
|---|---|---|
| Chemical Family | Mineraloid (Silica) | Borosilicate Mineral |
| Mohs Hardness | 5.5 - 6.5 | 7 - 7.5 |
| Crystal System | Amorphous | Trigonal |
| Key Feature | Play-of-Color | Spectrum of Colors |
| Care Level | Moderate (Avoid heat, dryness, impacts) | Low (Durable for most jewelry) |
Symbolism and Metaphysical Beliefs
Both opal and tourmaline are rich in symbolism and have been attributed with various metaphysical powers throughout history. Opal has long been associated with hope, innocence, and purity. Its shifting colors are said to inspire creativity, spontaneity, and emotional expression. In modern crystal healing practices, opal is often used to enhance self-confidence and to bring about a sense of calm and clarity. It is also considered a stone of love and passion, particularly in its fiery red and orange varieties.
Tourmaline, with its rainbow of colors, carries a broader spectrum of symbolic meanings. Pink tourmaline is strongly associated with love, compassion, and emotional healing. It is believed to open the heart chakra and attract love in both the material and spiritual realms. Black tourmaline is one of the most powerful protective stones, thought to repel and block negative energies and psychic attacks. Green tourmaline is linked to life force energy, vitality, and success. Watermelon tourmaline is considered a stone of reconciliation and balance, harmonizing the heart and mind. Across its varieties, tourmaline is seen as a stone of purification, cleansinging the body and spirit of negative influences.
Care and Cleaning
The significant difference in durability between opal and tourmaline dictates very different care requirements. Opal is a delicate gemstone and must be handled with care. It is best suited for pieces that are not subject to hard wear, such as pendants and earrings. Cleaning opal should be done gently with warm water, a mild soap, and a soft brush. It is critical to avoid ultrasonic cleaners, steam cleaners, and harsh chemicals, as these can damage or even destroy the stone. Sudden temperature changes should also be avoided. For opals with a high water content, it is important to store them in a stable, moderately humid environment to prevent crazing.
Tourmaline, by contrast, is quite resilient and is generally easy to care for. Its hardness makes it resistant to everyday scratches. It can be safely cleaned with warm, soapy water and a soft brush. While it is generally stable, some tourmaline varieties may have been fracture-filled or treated with heat or irradiation to enhance their color. Therefore, it is still prudent to avoid ultrasonic and steam cleaners unless you are certain of the stone's history and any treatments it has undergone.
Conclusion
October's birthstones, opal and tourmaline, offer a remarkable study in contrast. Opal, the traditional choice, captivates with its ethereal play-of-color, a phenomenon born from water and silica, embodying hope and creativity. Its softer nature demands a respectful and careful approach. Tourmaline, the modern addition, showcases the power of crystalline complexity, presenting an unparalleled spectrum of colors and offering a durable and versatile option for jewelry. From the ancient Roman belief in opal as the queen of gems to the Chinese Empress's passion for pink tourmaline, both stones have woven themselves into the fabric of human history and culture. Whether drawn to the mystical, shifting fire of opal or the vibrant, protective energy of tourmaline, those born in October are represented by two of the most colorful and fascinating gemstones on Earth.