October boasts not one, but two captivating birthstones: opal and tourmaline. Both gemstones are celebrated for their remarkable range of colours and fascinating histories, offering a vibrant choice for those born in the tenth month. This article delves into the unique characteristics, historical significance, geological origins, and symbolism of these radiant gems, drawing exclusively from available sources.
A History of Shifting Colours and Imperial Favour
The story of opal stretches back to ancient times. Its name is believed to originate from the Sanskrit word upala, meaning “precious stone,” used in India, the original source of opals traded westward. The Romans referred to it as opalus. Throughout history, opal has been imbued with diverse meanings and beliefs. Ancient Bedouins believed opals contained lightning, falling from the sky during thunderstorms, while the ancient Greeks associated the stone with prophecy and protection from disease. In Europe, opal became a symbol of purity, hope, and truth, and was once thought to embody the virtues of all coloured stones. It is also traditionally given as the gift for the 14th wedding anniversary.
Tourmaline’s history, while also rich, has a slightly different trajectory. For centuries, tourmaline was often misidentified as other gemstones due to its wide spectrum of colours. A notable example is the “Caesar’s Ruby” in the Russian crown jewels, which is, in fact, a red tourmaline (rubellite). Green tourmaline crystals discovered in Brazil during the 1500s were initially mistaken for emeralds. It wasn’t until the 19th century that tourmaline was formally recognised as a distinct mineral species. More recently, in the late 1800s, the Chinese Empress Dowager Tzu-Hsi developed a profound fondness for pink tourmaline, acquiring nearly the entire production from a California mine. Her devotion continued after her death, as she was buried with a pink tourmaline pillow, and the remainder of her collection was crafted into exquisite carvings.
Geological Formation and Sources
Opals are formed from silica and water within the Earth’s crust. The majority of the world’s opal originates in Australia, though significant deposits are also found in Mexico and, historically, in India. Mexican fire opal, a particularly vibrant variety, emerged as a significant source only in the mid-nineteenth century, and remains relatively limited in availability.
Tourmaline, conversely, forms in distinctive prism-like crystals with long hexagonal structures. It occurs naturally in a diverse range of geological environments and contains a variety of elements. While tourmaline is found in many locations, specific sources are noted for particular colours. California was a significant source for pink tourmaline, attracting the attention of Empress Tzu-Hsi. Brazil was also an early source of tourmaline, with green crystals initially mistaken for emeralds.
Gemological Properties: A Kaleidoscope of Characteristics
Both opal and tourmaline exhibit a remarkable diversity of gemological properties, contributing to their unique appeal.
Opal is prized for its “play-of-colour,” a shifting display of rainbow hues. This phenomenon is difficult to describe adequately, with comparisons drawn to fireworks, galaxies, and volcanoes. The value of opal is determined by the evenness and vibrancy of its base colour and the intensity of its play-of-colour. There are several types of opal, including:
- Fire Opal: Characterized by red, orange, or yellow backgrounds, often lacking play-of-colour.
- Crystal Opal: Transparent with superior play-of-colour effects.
- Water Opal: Displays a subtle background hue with play-of-colour.
Unlike most gemstones, fire opal is exempt from the traditional classification of “precious” versus “potch” (common opal) due to its value being derived from its base colour rather than play-of-colour.
Tourmaline is equally diverse in its properties. It is known for its wide range of colours, including pink, red, green, and blue, and can even exhibit multiple colours within a single crystal – a variety known as “watermelon tourmaline.” Most tourmalines found in jewellery consist primarily of the mineral elbaite. The colour variations are due to the presence of different elements within the crystal structure.
The following table summarizes key properties:
| Property | Opal | Tourmaline |
|---|---|---|
| Chemical Formula | Hydrated amorphous silica (SiO₂·nH₂O) | Complex borosilicate (variable) |
| Play-of-Colour | Present in many varieties | Absent |
| Transparency | Transparent to opaque | Transparent to opaque |
| Hardness (Mohs) | 5.5 - 6.5 | 7 - 7.5 |
| Colour Range | All colours, often iridescent | Pink, red, green, blue, multicoloured |
Symbolism and Metaphysical Beliefs
Throughout history, both opal and tourmaline have been attributed with various symbolic meanings and metaphysical properties.
Opal has long been associated with hope, purity, and truth. Ancient beliefs suggest it could bestow the gift of prophecy and protect against disease. More recently, some sources suggest black tourmaline protects the wearer from negativity and increases self-confidence.
Tourmaline’s symbolism varies depending on its colour. Pink tourmaline is associated with compassion and gentleness, embodying love. Green tourmaline is believed to promote courage, strength, and stamina. Black tourmaline is thought to offer protection and boost self-confidence.
Care and Cleaning
Due to their differing hardness levels, opal and tourmaline require different care. Opal, with a Mohs hardness of 5.5-6.5, is relatively soft and susceptible to scratches. It should be handled with care and protected from impacts. Tourmaline, with a hardness of 7-7.5, is more durable but still requires careful handling to avoid damage.
Both gemstones can be cleaned with warm, soapy water and a soft cloth. Avoid harsh chemicals, ultrasonic cleaners, and steam cleaners, as these can damage the stones. Opal, in particular, should not be subjected to prolonged exposure to water, as it can dehydrate and crack.
The Standardization of Birthstones
The current list of birthstones, including the designation of opal and tourmaline for October, was created by the National Association of Jewellers in 1952 to standardize birthstone assignments. This list has been modified over time to reflect changing styles and the availability of gemstones. The addition of tourmaline to October’s birthstone list was partly influenced by perceptions that opal was too feminine or lacked sufficient durability.
Conclusion
Opal and tourmaline, the birthstones of October, represent a captivating duality of colour and history. From the ancient beliefs surrounding opal’s mystical properties to the imperial favour bestowed upon pink tourmaline, these gemstones have held a significant place in human culture for centuries. Their diverse geological origins, unique gemological properties, and varied symbolism make them cherished treasures for those born in October and gemstone enthusiasts alike. Their enduring appeal lies in their ability to capture the imagination and inspire a sense of wonder.