October is unique among the months, boasting not one, but two recognized birthstones: opal and tourmaline. Both gemstones offer a stunning array of colors and a rich history, making them cherished adornments for those born in the tenth month. While opal holds the distinction as the traditional October birthstone, tourmaline was added to the list in 1952, offering a wider spectrum of choice and reflecting evolving tastes in jewelry. This article will delve into the history, geological origins, gemological properties, and symbolism of both opal and tourmaline, providing a comprehensive overview of these captivating gemstones.
A History of Reverence and Recognition
Opal’s history stretches back millennia, with its origins traced to India, where it was known as “upala,” meaning precious stone. The Romans referred to it as “opalus.” Throughout history, opal has been imbued with diverse meanings. Ancient Bedouins believed opals contained lightning and fell from the sky during thunderstorms, while the ancient Greeks associated the gem with prophecy and protection from disease. In Europe, opal symbolized purity, hope, and truth, and was even believed to embody the virtues of all colored stones. It remains the stone traditionally given to celebrate the 14th wedding anniversary.
Tourmaline’s history is somewhat more recent in terms of formal recognition. For centuries, tourmaline crystals were often misidentified as other gemstones, such as emeralds and rubies. A red tourmaline featured in the Russian crown jewels was, in fact, mistaken for a ruby and became known as “Caesar’s Ruby.” It wasn’t until the 1800s that tourmaline was definitively recognized as a distinct mineral species. The name “tourmaline” itself originates from the Sri Lankan Sinhalese word “turamali,” meaning “stone with mixed colors,” a fitting description given the gem’s remarkable color range. The National Association of Jewellers added tourmaline as an official October birthstone in 1952, partly due to concerns that opal was considered too feminine or lacked durability.
Geological Formation and Global Sources
Opal’s formation is unique and often occurs in sedimentary environments. The gemstone is hydrated amorphous silica, meaning it contains water within its structure. It forms in cracks and voids within rocks, where silica-rich solutions seep in and deposit the silica. The “play-of-color,” opal’s most defining characteristic, is created by the diffraction of light as it passes through microscopic spheres of silica within the stone.
The most productive opal fields in the world are located in Australia, accounting for the vast majority of global opal production. However, significant deposits are also found in Ethiopia, Mexico, Brazil, Central Europe, Honduras, Indonesia, Madagascar, Peru, Turkey, and the United States. Each location contributes to the unique character and hues of the opal found there.
Tourmaline, on the other hand, forms in igneous and metamorphic rocks. It is a complex borosilicate mineral, and its diverse colors are attributed to trace elements within its chemical composition. Tourmaline crystallizes in a variety of forms, often exhibiting long, prismatic crystals.
Tourmaline is found in numerous locations worldwide. Brazil is a significant source, with discoveries dating back to the 1500s when green tourmaline was initially mistaken for emeralds. Other important sources include Sri Lanka, Africa, and the United States. Paraiba tourmaline, renowned for its vibrant neon blue and green colors, is primarily sourced from Brazil, though deposits have also been found in Nigeria and Mozambique.
Gemological Properties: A Comparative Look
Both opal and tourmaline possess distinct gemological properties that contribute to their beauty and desirability.
Opal:
- Chemical Formula: Hydrated amorphous silica (SiO₂·nH₂O)
- Hardness (Mohs Scale): 5.5 – 6.5
- Specific Gravity: 1.98 – 2.15
- Optical Phenomenon: Play-of-color (diffraction of light)
- Transparency: Typically translucent to opaque
Tourmaline:
- Chemical Formula: Complex borosilicate (XY₃Z₆(BO₃)₃Si₆O₁₈(OH,F)₄) – composition varies with color
- Hardness (Mohs Scale): 7 – 7.5
- Specific Gravity: 3.06 – 3.98 (varies with composition)
- Optical Phenomenon: Pleochroism (exhibits different colors when viewed from different angles)
- Transparency: Transparent to opaque
| Property | Opal | Tourmaline |
|---|---|---|
| Hardness | 5.5 - 6.5 | 7 - 7.5 |
| Chemical Formula | SiO₂·nH₂O | Complex Borosilicate |
| Key Characteristic | Play-of-Color | Color Variety |
Tourmaline’s hardness of 7 to 7.5 on the Mohs scale makes it a more durable gemstone than opal, which ranges from 5.5 to 6.5. This difference in hardness impacts their suitability for different types of jewelry; tourmaline is generally more appropriate for everyday wear, while opal may require more careful handling.
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. It was believed to inspire creativity and enhance intuition. The dramatic play-of-color was often likened to fireworks, galaxies, and volcanoes, symbolizing passion and transformation.
Tourmaline’s symbolism varies depending on its color. Pink tourmaline is associated with love, compassion, and gentleness. Black tourmaline is believed to protect against negativity and promote self-confidence. Green tourmaline is thought to foster courage, strength, and stamina. Ancient mystics believed that tourmaline could inspire artistic expression due to its diverse color palette.
Care and Cleaning
Due to their differing properties, opal and tourmaline require different care routines. Opal, being relatively softer and containing water, is susceptible to damage from heat and dehydration. It should be protected from direct sunlight, extreme temperatures, and harsh chemicals. Cleaning opal jewelry involves gently wiping it with a soft cloth and lukewarm soapy water. Avoid ultrasonic cleaners and prolonged soaking.
Tourmaline, being harder and more durable, is less prone to damage. It can be cleaned with warm soapy water and a soft brush. Ultrasonic cleaners are generally safe for tourmaline, but caution should be exercised with stones that have been fracture-filled.
Conclusion
Opal and tourmaline, the captivating birthstones of October, offer a diverse range of colors, histories, and symbolic meanings. Opal, with its iridescent play-of-color, embodies hope and inspiration, while tourmaline, with its remarkable color variety, represents love, protection, and strength. Whether chosen for their aesthetic beauty, historical significance, or metaphysical properties, these gemstones continue to enchant and captivate jewelry lovers and gemstone enthusiasts alike.