October is unique among the calendar months, boasting not one, but two recognized birthstones: opal and tourmaline. Both gemstones offer a stunning array of colors and captivating optical phenomena, making them cherished additions to the world of jewelry and gemstone collecting. While opal holds the distinction as the traditional October birthstone, tourmaline has risen to prominence as a modern alternative, reflecting evolving tastes and gemstone availability. This article will delve into the history, geological origins, gemological properties, and cultural significance of both opal and tourmaline, providing a comprehensive overview of these fascinating October birthstones.
History and Lore
The story of opal stretches back to antiquity. Its name is believed to originate from the Sanskrit word upala, meaning “precious stone,” adopted into the Roman opalus. Ancient Greeks associated opal with prophecy and protection from disease, referring to it as opallios, meaning “to see a change in color,” a direct reference to its characteristic play-of-color. Europeans, for centuries, considered opal a symbol of purity, hope, and truth, believing it embodied the virtues of all colored stones. Romans, similarly, viewed opal as a symbol of hope and love.
Tourmaline’s history, while also ancient, gained significant traction later. In the late 19th century, the Empress Dowager Tzu-Hsi of China developed a fervent passion for pink tourmaline, acquiring nearly the entire output from California mines. She was even buried with a pillow of pink tourmaline, and her remaining collection was crafted into intricate carvings.
The formalization of birthstone lists began in the 19th century. Tiffany & Co. published a pamphlet of “Gregorian Birthstone Poems” in 1870, assigning opal to October. The National Association of Jewelers (now Jewelers of America) initially designated opal as the sole October birthstone in 1912. However, in 1952, the association curated a revised list, and in subsequent years, tourmaline was added as a co-birthstone, particularly pink tourmaline, to address concerns about opal’s durability and cater to modern preferences.
Geological Formation and Sources
Opal is not a true crystal but a mineraloid – a material with a crystalline structure but lacking a defined crystal lattice. It is formed from the gradual natural heating of silica gel found in cracks and voids within rocks. As the silica gel dries, microscopic silica spheres accumulate, creating the characteristic play-of-color. While once sourced primarily from India, Australia is now the world’s leading producer of opal, with significant deposits also found in Ethiopia, Mexico, and the United States.
Tourmaline, conversely, is a crystalline borosilicate mineral. It forms in distinctive prism-like crystals with long hexagonal structures. The diverse range of colors in tourmaline arises from trace elements within its chemical composition. Tourmaline crystals can even exhibit multiple colors within a single stone, known as watermelon tourmaline. While found globally, significant sources include Brazil, Sri Lanka, Nigeria, and the United States (California and Maine).
Gemological Properties
Opal: Opal’s defining characteristic is its “play-of-color,” a phenomenon caused by the diffraction of light through microscopic silica spheres. This creates flashes of rainbow hues that shift and change with the viewing angle. Opals are categorized as either precious or common, based on the presence or absence of this play-of-color. Precious opals display vibrant colors, while common opals lack this effect.
Tourmaline: Tourmaline exhibits a wide range of colors, including pink, green, blue, black, and even colorless. The most common variety is black tourmaline. Most jewelry-grade tourmalines consist primarily of the mineral elbaite. Tourmaline’s hardness varies depending on its composition, but generally ranges from 7 to 7.5 on the Mohs scale. Pink tourmaline, the modern October birthstone, is particularly prized for its delicate hues.
The following table summarizes key gemological properties:
| Property | Opal | Tourmaline |
|---|---|---|
| Chemical Formula | Hydrated amorphous silica (SiO₂·nH₂O) | Complex borosilicate (variable) |
| Hardness (Mohs) | 5.5 – 6.5 | 7 – 7.5 |
| Specific Gravity | 1.98 – 2.50 | 3.06 – 3.98 |
| Optical Phenomenon | Play-of-color | Pleochroism (some varieties) |
| Crystal System | Amorphous | Trigonal |
Symbolism and Metaphysical Beliefs
Throughout history, both opal and tourmaline have been imbued with symbolic meaning. Opal has been associated with confidence, hope, and creativity. Ancient cultures believed it held prophetic powers and offered protection from disease.
Tourmaline, particularly pink tourmaline, is often linked to love, compassion, and emotional healing. It is believed to promote self-love and reduce stress. The diverse colors of tourmaline also contribute to its varied metaphysical associations; green tourmaline is linked to growth and abundance, while black tourmaline is considered a protective stone.
Care and Cleaning
Due to its relatively lower hardness, opal is more susceptible to scratches and damage than tourmaline. It should be stored separately from harder gemstones to avoid abrasion. Cleaning opal involves gentle washing with mild soap and warm water; avoid harsh chemicals or ultrasonic cleaners.
Tourmaline is more durable and can withstand more rigorous cleaning. It can be cleaned with warm soapy water, a soft brush, and rinsed thoroughly. Ultrasonic cleaners are generally safe for tourmaline, but caution should be exercised with stones that have been fracture-filled.
The Evolution of October’s Birthstone Designation
The inclusion of two birthstones for October reflects a shift in the jewelry industry and consumer preferences. Originally, opal held sole claim to the month. However, concerns about its durability and a desire to offer more variety led to the addition of tourmaline. This dual designation provides October-born individuals with a choice that reflects their personal style and preferences. The story of October’s birthstones is a testament to the enduring appeal of gemstones and the evolving relationship between humans and the natural world.
Conclusion
Opal and tourmaline, the captivating birthstones of October, represent a rich tapestry of history, geological wonder, and cultural significance. From ancient beliefs in their protective powers to modern appreciation for their breathtaking beauty, these gemstones continue to enchant and inspire. Whether drawn to the shifting colors of opal or the vibrant hues of tourmaline, those born in October are fortunate to have two exceptional gemstones to celebrate their birth month.