October is a month marked by a unique distinction in the world of birthstones: it is one of the few months associated with two gemstones—opal and tourmaline. While many months are assigned a single stone, October reflects the evolving traditions and practices of the gemstone industry, which has expanded to include multiple stones when necessary. This dual designation not only reflects the rich diversity of available gemstones but also highlights the importance of October’s birthstones in both historical and modern contexts.
This article will explore the characteristics, history, symbolism, and cultural significance of these two captivating stones. From their geological origins to their use in jewelry and their place in various belief systems, we will uncover what makes opal and tourmaline so special to those born in October.
History and Lore
The practice of assigning gemstones to specific months dates back centuries, with roots in ancient religious texts, such as the Biblical Breastplate of Aaron, which listed twelve stones to represent the twelve tribes of Israel. Over time, these associations evolved, particularly in Western cultures, where the National Association of Jewelers (NAJ) played a key role in standardizing the list of birthstones in 1952. This list has since been updated to reflect changing fashion trends and the availability of gemstones.
In 1952, the NAJ included opal as the October birthstone. However, due to questions about its durability and perceived femininity, tourmaline was later added to the list. This dual designation reflects a more inclusive and practical approach, acknowledging the wide range of gemstones that can represent October.
Opal: The Stone of the Rainbow
Opal has a long and storied history. Known as Upala in ancient India, it was one of the first gemstones imported into the Western world. In ancient Rome, it was called opalus, and it was highly prized for its play-of-color—a phenomenon where the stone displays a shifting spectrum of colors when moved under light. This effect, sometimes compared to fireworks, galaxies, or lightning, made opal a symbol of mystery and wonder.
Opal was revered by ancient Greeks, who believed it contained the virtues of all colored stones and had prophetic powers. The Bedouins of the desert believed opal contained lightning, and that it fell from the sky during thunderstorms. In Europe, opal was associated with purity, truth, and hope, and it was even used as a 14th-anniversary gift.
Despite its beauty, opal has often been the subject of superstition. In the 15th century, a French writer described it as a "gem of the devil", and in the 19th century, British author Sir Walter Scott wrote a novel titled Anne of Geierstein, which portrayed opal as an omen of death. These negative associations led to a decline in opal’s popularity in some regions, but its allure has persisted in others, especially in Australia, where it is naturally abundant.
Tourmaline: The Stone of Mixed Colors
Tourmaline, like opal, has a fascinating history. Its name comes from the Sinhalese word "toramalli", meaning "stone with mixed colors", a fitting description for a gemstone that comes in a vast array of colors, from deep reds and greens to striking pinks and blues. This diversity has led to misidentification in the past. For example, a red tourmaline was once mistaken for a ruby in the Russian Crown Jewels, where it was known as the "Caesar's Ruby".
Tourmaline was first recognized as a distinct mineral in the 19th century, after centuries of being confused with other gemstones. The green tourmalines discovered by Spanish conquistadors in Brazil in the 1500s were initially believed to be emeralds, but later studies confirmed their identity as tourmaline.
Throughout history, tourmaline has been associated with healing and spiritual properties. Black tourmaline is believed to ward off negativity, while pink tourmaline symbolizes love and compassion. Green tourmaline is thought to promote courage and strength. These associations reflect the emotional and physical diversity of the stone, making it a popular choice for those seeking emotional balance.
Geological Formation and Sources
Opal: A Unique Silica-Based Gem
Opal is not a true mineral in the traditional sense, but rather a hydrous amorphous form of silica (SiO₂·nH₂O). Unlike most gemstones, which have a crystalline structure, opal is composed of tiny silica spheres arranged in a three-dimensional lattice. These spheres diffract light, producing the play-of-color that makes opal so visually striking.
Opals form in volcanic and sedimentary environments, particularly in cavities and cracks within rock formations. The most widely accepted theory of opal formation involves silica-rich water seeping through the earth and depositing layers of silica gel. Over time, as water evaporates and acidity changes, this gel hardens into solid opal.
There are two main types of opal:
- Precious opal, known for its play-of-color.
- Common opal, which does not exhibit this effect.
Opal is also known to form as a replacement for fossils, when original organic material (such as shells, bones, or wood) dissolves and is replaced by silica.
The most famous opal-producing countries are:
- Australia, which is responsible for 90% of the world’s precious opal.
- Ethiopia, known for its "Ethiopian opal", which is hydrophane (able to absorb water).
- Brazil, Mexico, and the United States also produce notable opals.
Tourmaline: A Versatile Mineral
Tourmaline is a borosilicate mineral with a complex chemical formula, which can vary depending on the colors and trace elements present. Its general formula is:
$$ A\left(B3O3\right)\left(Si6O{18}\right)\left(XY3Z6\right) $$
Where the letters represent different elements that can be present in the crystal structure. This chemical variability is why tourmaline can come in such a wide range of colors.
Tourmaline typically forms in pegmatite deposits, which are coarse-grained igneous rocks that allow for the slow crystallization of minerals. These deposits are rich in boron and other trace elements, which contribute to the color diversity of tourmaline.
The most well-known tourmaline varieties include:
- Rubellite (red tourmaline)
- Paraíba tourmaline (green-to-blue, high in copper)
- Chrome tourmaline (deep green, high in vanadium)
- Black tourmaline (schorl)
- Pink tourmaline (dravite or elbaite)
The most famous sources of tourmaline are:
- Brazil, particularly the Paraíba region, which is known for producing vivid green-to-blue tourmalines.
- Nigeria, where Paraíba-type tourmaline is also found.
- Afghanistan, China, and the United States, which produce a wide range of tourmaline colors.
Gemological Properties
Opal
| Property | Value |
|---|---|
| Chemical Formula | SiO₂·nH₂O |
| Hardness (Mohs Scale) | 5–6.5 |
| Specific Gravity | 1.9–2.3 |
| Refractive Index | 1.34–1.50 |
| Transparency | Transparent to opaque |
| Color | Multicolored (play-of-color in precious opal) |
| Luster | Vitreous to waxy |
| Cleavage | None |
| Special Properties | Play-of-color, water-sensitive |
Opal is not a mineral in the traditional sense, as it lacks a crystalline structure. Instead, it is an amorphous form of hydrated silica, which makes it relatively soft and fragile. It is also hydrophilic, meaning it absorbs water, which can affect its durability and appearance.
Opal is prone to cracking and dehydration, especially if exposed to high heat or dry environments. This is why it is often set in protective settings and stored in a humid environment.
Tourmaline
| Property | Value |
|---|---|
| Chemical Formula | Varies (e.g., Na(LiAl)Si₂O₆ for elbaite) |
| Hardness (Mohs Scale) | 7–7.5 |
| Specific Gravity | 3.0–3.2 |
| Refractive Index | 1.62–1.64 |
| Transparency | Transparent to opaque |
| Color | Wide range (red, green, blue, black, pink, etc.) |
| Luster | Vitreous |
| Cleavage | Perfect in one direction |
| Special Properties | Piezoelectric and pyroelectric properties |
Tourmaline is a mineral in the beryl family, and it is known for its piezoelectric and pyroelectric properties, meaning it can generate an electric charge when subjected to pressure or heat. This property was once used in electronic devices, though modern technology has largely replaced it.
Tourmaline is harder and more durable than opal, making it more suitable for everyday jewelry. Its wide range of colors makes it a versatile choice for designers, and its cleavage means it must be cut carefully to avoid damage.
Symbolism and Metaphysical Beliefs
Opal
Opal has long been associated with mystery, intuition, and emotional balance. In ancient Greece, it was believed to contain the virtues of all colored stones, making it a powerful symbol of unity and harmony. The Aztecs believed opal was a stone of destruction and creation, symbolizing the cycle of life and rebirth.
In Europe, opal was considered a stone of purity, truth, and hope, and it was often used in wedding jewelry to symbolize faithfulness and enduring love. During the Victorian era, opal was a popular gemstone, and it was believed to enhance intuition and psychic abilities.
However, opal has also had a controversial reputation. In the 19th century, it was often associated with bad luck, and British author Sir Walter Scott even wrote a novel in which opal was a symbol of death. This led to a decline in its popularity in some regions, though it remains a beloved gemstone in Australia and other parts of the world.
Tourmaline
Tourmaline is known for its diverse symbolism, reflecting the wide range of colors it comes in. Black tourmaline is considered a stone of protection, believed to ward off negative energy and promote self-confidence. Pink tourmaline is associated with love, compassion, and emotional healing, making it a popular choice for those seeking emotional balance.
Green tourmaline is believed to promote courage, strength, and vitality, making it a stone of personal power. Blue tourmaline is associated with communication and clarity, while red tourmaline is believed to stimulate passion and creativity.
Tourmaline is also associated with spiritual growth and emotional stability, and it is often used in energy healing practices. It is believed to ground and stabilize the wearer, helping them to stay centered and focused.
Care and Cleaning
Both opal and tourmaline require special care due to their unique physical properties.
Opal
- Avoid high heat and dry environments, as opal is hygroscopic and can dry out and crack.
- Store opal in a cool, humid place, such as a closed jewelry box with a damp cloth.
- Avoid exposure to harsh chemicals, including ammonia and acids, which can damage the surface.
- Clean opal with a soft, damp cloth using mild soap and water. Do not use ultrasonic or steam cleaners, as these can damage the stone.
Tourmaline
- Tourmaline is more durable than opal, with a hardness of 7–7.5, but it is prone to cleavage, so it should be handled with care.
- Avoid exposure to high heat, as it can alter the color of some tourmalines, especially paraíba and chrome tourmalines.
- Clean tourmaline with a soft cloth and mild soap, and avoid abrasive materials.
- Ultrasonic and steam cleaners can be used with caution, but ultrasonic cleaners may cause stress due to vibrations along the cleavage planes.
Conclusion
October is a month of dual gemstone blessings, with opal and tourmaline as its birthstones. These two stones represent a rich blend of history, beauty, and symbolism, and their inclusion in the birthstone list reflects the evolving nature of gemstone traditions.
Opal, with its play-of-color and ethereal beauty, has captivated people for centuries. Despite its delicate nature, it remains a symbol of mystery and transformation, valued for its spiritual and emotional properties. Tourmaline, on the other hand, is a versatile and durable gemstone, known for its wide range of colors and healing properties. Its scientific properties, such as piezoelectricity and pyroelectricity, add to its fascination and value.
Together, these stones make October a month of vibrant color and deep meaning, offering a rich legacy for those born under its sign. Whether worn as jewelry, used in energy healing, or simply admired for its beauty, opal and tourmaline continue to inspire and enchant gemstone lovers around the world.