October is unique among the months, possessing not one, but two recognized birthstones: opal and tourmaline. Both gemstones offer a stunning array of colors and optical phenomena, making them highly prized by collectors and jewelry enthusiasts alike. While opal holds the distinction as the traditional October birthstone, tourmaline was formally recognized as a modern alternative in 1912, offering a wider range of choices for those born in the tenth month. This article will delve into the history, geological origins, gemological properties, symbolism, and care of these captivating gemstones.
History and Lore
The story of October’s birthstones is one of evolving tradition. The earliest records indicate opal as the sole stone associated with the month. The name “opal” is believed to originate from the Sanskrit word upala, meaning “precious stone,” and was adopted into Roman language as opalus. Ancient civilizations attributed various powers to opal. Bedouins believed opals contained lightning and fell from the sky during thunderstorms, while ancient Greeks associated the gem with prophecy and protection from disease. Europeans considered opal a symbol of purity, hope, and truth, believing it embodied the virtues of all colored stones.
Tourmaline’s history is somewhat more recent in terms of its association with October. Formalized birthstone lists began to emerge in the late 19th century, with Tiffany & Co. publishing a pamphlet in 1870 designating opal for October. However, the National Association of Jewellers (now Jewellers of America) in 1912 officially recognized tourmaline as an alternative birthstone for the month.
Notably, the late 19th century saw a surge in demand for pink tourmaline, particularly from the Chinese Empress Dowager Tzu-Hsi, who acquired nearly the entire production from California mines. She valued the stone so highly that she was buried with a pink tourmaline pillow, and the remainder of her collection was crafted into intricate carvings.
Geological Formation and Sources
Both opal and tourmaline have distinct geological origins. Opal is unique in that it is not a crystalline mineral like most gemstones. Instead, it is a hydrated amorphous form of silica, meaning it lacks a defined crystal structure. It forms from silica-rich water that seeps into cracks and voids in the earth, depositing microscopic spheres of silica. The size and arrangement of these spheres determine the play-of-color, the characteristic iridescent effect for which opal is famous. Significant opal deposits are found in Australia, but also in Mexico, where “fire opal” – characterized by its red, orange, or yellow background – is sourced. Crystal opal, known for its transparency and superior play-of-color, is also highly valued. Water opal, a more affordable option, exhibits a subtle play-of-color.
Tourmaline, on the other hand, is a crystalline borosilicate mineral. It forms in pegmatites, which are coarse-grained igneous rocks, and in metamorphic rocks. The diverse chemical composition of tourmaline results in a wide range of colors. Most jewelry-quality tourmaline consists of the elbaite variety, forming in distinctive prism-like crystals with long hexagonal structures. While tourmaline occurs in many locations globally, specific varieties are associated with particular regions. Pink tourmaline, the modern October birthstone, has been historically sourced from California, while fire opal is primarily found in Mexico.
Gemological Properties
Opal’s properties differ significantly from those of tourmaline. Opal’s hardness ranges from 5.5 to 6.5 on the Mohs scale, making it relatively soft and susceptible to scratches. Its specific gravity typically falls between 1.98 and 2.20. The defining characteristic of opal is its play-of-color, caused by the diffraction of light through the silica spheres. This effect is not present in all opals; fire opal, for example, is valued for its vibrant body color rather than its play-of-color.
Tourmaline, in contrast, boasts a hardness of 7 to 7.5 on the Mohs scale, making it considerably more durable than opal. Its specific gravity ranges from 3.02 to 3.22. Tourmaline exhibits strong pleochroism, meaning it displays different colors when viewed from different angles. This property is particularly noticeable in some tourmaline varieties. As a corundum gem, like ruby, it occurs in a full rainbow variety of colors, except red. The term "tourmaline" on its own typically refers to the blue variety, but it is marketed according to its color (e.g., yellow sapphire, purple sapphire). Some tourmaline crystals even exhibit dichroism, displaying multiple colors within a single crystal, known as “watermelon tourmaline.”
The following table summarizes key gemological properties:
| Property | Opal | Tourmaline |
|---|---|---|
| Hardness (Mohs) | 5.5 - 6.5 | 7 - 7.5 |
| Specific Gravity | 1.98 - 2.20 | 3.02 - 3.22 |
| Crystal System | Amorphous | Trigonal |
| Play-of-Color | Often Present | Absent |
| Pleochroism | Absent | Present |
Symbolism and Metaphysical Beliefs
Throughout history, both opal and tourmaline have been imbued with symbolic meaning. As previously mentioned, opal was historically associated with purity, hope, and truth, and believed to bestow prophetic abilities and protection from disease.
Tourmaline, while having a shorter history as a birthstone, is also associated with positive attributes. Sapphires, of which tourmaline is a variety, are considered protective gemstones, shielding the wearer from harm and negative intentions. Blue sapphires, in particular, were highly regarded by priests for their spiritual significance. Tourmaline is also believed to promote emotional healing and balance.
Care and Cleaning
Due to their differing hardness levels, opal and tourmaline require different care routines. Opal, being relatively soft, is susceptible to scratches and should be handled with care. It is advisable to avoid wearing opal jewelry during activities that could cause impact or abrasion. Cleaning opal should be done gently with a soft cloth and lukewarm soapy water. Avoid ultrasonic cleaners and harsh chemicals, as these can damage the stone.
Tourmaline, being more durable, can withstand more rigorous wear. However, it is still advisable to avoid harsh impacts and chemicals. Cleaning tourmaline can be done with warm soapy water and a soft brush. Ultrasonic cleaners can be used with caution, but avoid subjecting tourmaline to sudden temperature changes.
Conclusion
Opal and tourmaline, the dual birthstones of October, represent a captivating blend of history, geological wonder, and symbolic meaning. Opal, with its ethereal play-of-color, embodies hope and inspiration, while tourmaline, with its diverse hues and durability, symbolizes protection and emotional balance. Whether one prefers the traditional allure of opal or the modern vibrancy of tourmaline, these gemstones offer a beautiful and meaningful connection to the tenth month of the year.