October boasts the unique distinction of having two recognized birthstones: the captivating opal and the richly colored tourmaline. Both gemstones offer a stunning array of hues and optical phenomena, making them popular choices for jewelry and cherished possessions. While opal traditionally held the sole designation as October’s birthstone, tourmaline was officially added as an alternative in 1912 by the National Association of Jewellers, now known as Jewellers of America. This article will delve into the history, geological origins, gemological properties, and cultural significance of both opal and tourmaline, exploring their enduring appeal as symbols of October.
History and Lore
The association of gemstones with specific months and zodiac signs dates back to ancient times, though the formalized lists we recognize today are relatively recent. The earliest standardized lists emerged in 1870 with the publication of “Gregorian Birthstone Poems” by Tiffany & Co., which initially featured opal as October’s sole birthstone. Prior to this, various cultures attributed different meanings and powers to gemstones, often based on their color and perceived resemblance to natural phenomena.
Ancient Romans associated opals with purity, hope, and perspective, referring to them as cupid paederos, or “child as beautiful as love.” Conversely, despite positive associations in some cultures, opals experienced a period of superstition in the 19th century, wrongly believed to be cursed unless worn by those born in October. Chinese cultures, however, traditionally viewed opals as symbols of good luck.
Tourmaline’s history is somewhat less documented in ancient lore, but its name originates from the Sinhalese word toramalli, meaning “mixed gems,” reflecting the stone’s diverse color range. Green tourmalines were historically mistaken for emeralds, and in the late 1800s, pink tourmaline gained prominence as an “American Gem” thanks to the efforts of Tiffany & Co.’s gemologist, George F. Kunz.
Geological Formation and Sources
Opals are formed from seasonal rains that seep into the ground, dissolving silica in ancient underground rock formations. This process is particularly prevalent in regions like Australia’s semi-desert “outback.” As the water evaporates during dry periods, solid deposits of silica accumulate in cracks and layers within sedimentary rock. Over approximately five million years, this silica solidifies, creating the mesmerizing play of color characteristic of opals. Over 95% of the world’s fine opals originate in Australia, with varieties including precious opals, white opals, boulder opals, crystal opals, and fire opals.
Tourmaline’s formation occurs in a variety of geological environments, resulting in its diverse chemical composition and color variations. The stone can become magnetic under heat or pressure, a phenomenon known as pyroelectricity. Different varieties of tourmaline are distinguished by their color, including chrome tourmaline (deep green), rubellite tourmaline (red), kunzite or pink tourmaline (pink), Paraíba tourmaline (bluish-green), Savannah tourmaline (yellow to orange), watermelon tourmaline (pink center with green outer ring), and parti-colored tourmaline (displaying multiple colors).
Gemological Properties
Both opal and tourmaline exhibit unique gemological properties that contribute to their beauty and value.
Opal: Precious opals are characterized by their play of color, created by the diffraction of light as it passes through microscopic silica spheres. The background color of an opal is determined by impurities within the silica, while the play of color arises from the way silica forms together, creating tiny gaps that diffract light. Opals are typically cut into cabochons or beads, though fire opals can be faceted. Transparency ranges from translucent to opaque, with black opals generally being more opaque.
Tourmaline: Tourmaline’s chemical formula is complex and varies depending on the specific variety. It exhibits a wide range of colors, with the rarest and most valuable being Paraíba tourmaline. Other valuable colors include black, red, and pink. Tourmalines are often faceted, particularly in long rectangular shapes, with brilliant cuts favored for more valuable varieties. Clarity generally falls into Type II, meaning minor inclusions are expected, though some varieties like chrome and green tourmalines are Type I (usually inclusion-free), while others like Paraíba, rubellite, and watermelon tourmaline are Type III (always visibly included).
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 |
| Transparency | Translucent to opaque | Transparent to opaque |
| Typical Cut | Cabochon, bead | Faceted, cabochon |
| Play of Color | Present in precious opals | Absent |
| Pyroelectric | Absent | Present |
Symbolism and Metaphysical Beliefs
Both opal and tourmaline are imbued with symbolic meanings and purported metaphysical properties.
Opal is often associated with purity, hope, and perspective. It is believed to possess healing powers related to vision and the mind, potentially treating eyesight problems, boosting cognitive abilities, and even offering glimpses into the future. Despite past superstitions, many still consider opal a lucky stone.
Tourmaline, as a whole, symbolizes compassion, open-mindedness, and forgiveness, earning it the nickname “Stone of Reconciliation.” Different colors of tourmaline are believed to have specific healing properties. Pink tourmaline, for example, is said to boost energy, encourage love, and smooth relationship troubles.
Care and Cleaning
Due to their differing hardness levels, opal and tourmaline require different care approaches. Opal, with a Mohs hardness of 5.5-6.5, is relatively soft and susceptible to scratches. It should be stored separately from harder gemstones and cleaned with a soft cloth and mild soapy water. Avoid ultrasonic cleaners and harsh chemicals.
Tourmaline, with a hardness of 7-7.5, 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 significant inclusions.
Conclusion
Opal and tourmaline, the dual birthstones of October, represent a captivating blend of history, geological wonder, and symbolic meaning. From the ancient Roman association of opal with love and hope to the modern recognition of tourmaline’s healing properties, these gemstones continue to enchant and inspire. Whether chosen for their aesthetic beauty, their perceived metaphysical benefits, or simply as a celebration of an October birthday, opal and tourmaline remain cherished symbols of this vibrant month.