October, the tenth month of the year, holds a unique distinction in the world of birthstones: it is the only month officially recognized with two gemstones—opal and tourmaline. While the majority of months are associated with a single birthstone, October’s duality reflects both the richness of gemological diversity and the cultural and historical evolution of birthstone traditions. This duality is not unique to October alone, as months like June, November, and December also have multiple birthstone options in the modern list. However, October’s pairing of opal and tourmaline has captured the imagination of gemstone lovers for centuries, and the two stones continue to be cherished for their beauty, symbolism, and varied applications in jewelry.
This article explores the historical background, gemological properties, cultural significance, and practical considerations of October’s two birthstones—opal and tourmaline. Drawing on a range of authoritative and historical sources, it provides a detailed account of how these gemstones came to represent October and what they signify in both traditional and modern contexts.
History and Lore
The concept of birthstones is ancient, with roots stretching back to biblical times. In the Old Testament, the High Priest’s breastplate was adorned with twelve stones, each representing a tribe of Israel. These were interpreted as the foundation of the modern birthstone calendar. However, the modern association of specific gemstones with each month began to take shape in the 19th and 20th centuries.
The modern birthstone list was formalized in 1912 by the National Association of Jewelers (now the Jewelers of America). At that time, opal was designated as the primary birthstone for October, and tourmaline was included as an alternative. This decision was influenced by the gemstones’ popularity and cultural significance in the early 20th century.
Opal had long been associated with October. It was featured in a poem published by Tiffany & Co. in 1870, which described the gemstone as a symbol of hope and purity. The poem, part of a series of “Gregorian Birthstone Poems,” helped cement opal’s place as a prominent birthstone. Meanwhile, tourmaline, with its rich and varied colors, was also gaining recognition for its beauty and versatility in jewelry.
The inclusion of both opal and tourmaline in the official list reflects the gemological and cultural diversity of the time. Opal’s iridescent play of color made it a favorite among European royalty, including Queen Victoria, who was known for her love of opal jewelry. Tourmaline, on the other hand, was becoming increasingly popular in the United States for its durability and wide range of colors.
It is also worth noting that October is not the only month with multiple birthstones. For instance, June has both pearl and alexandrite, and November has topaz and citrine. However, October’s pairing of opal and tourmaline is particularly notable due to the distinct visual and symbolic qualities of each stone.
Geological Formation and Sources
Opal
Opal is a hydrous amorphous form of silica, meaning it lacks the crystalline structure of most gemstones. Instead, opal is formed when silica-rich water seeps into cracks in rocks and evaporates, leaving behind a silica gel that hardens over time. The unique play of color seen in precious opal is due to the microscopic arrangement of silica spheres that diffract light into a spectrum of colors.
The most famous source of opal is Australia, which produces over 90% of the world’s precious opal. Opal mining in Australia began in the late 19th century, and the country is known for its high-quality black opals and crystal opals. Other notable opal-producing countries include Ethiopia, Mexico, Brazil, and Indonesia.
Opal is typically cut into a cabochon, a smooth, rounded shape that showcases its play of color, rather than being faceted like other gemstones. This is because opal’s structure makes it unsuitable for faceting and also because its colors are best displayed in a smooth surface.
Tourmaline
Tourmaline is a borosilicate mineral that comes in a wide range of colors, often within a single stone. This is due to the presence of different trace elements that influence the color of the gemstone. The most famous and valuable variety is Paraíba tourmaline, which is known for its striking neon blue-green color. It was first discovered in Paraíba, Brazil, in the 1980s, and later found in Nigeria and Mozambique.
Tourmaline forms in pegmatite and metamorphic rocks, where it crystallizes under high-temperature conditions. The mineral is composed of a complex chemical structure that includes elements like aluminum, boron, and oxygen, as well as trace elements like manganese, iron, and copper, which affect the color of the stone.
Tourmaline is generally harder than opal, with a Mohs hardness of 7 to 7.5, making it more suitable for everyday wear in jewelry. This is one of the reasons why tourmaline is often considered a more practical alternative to opal for rings and other frequently worn pieces.
The most significant sources of tourmaline include Brazil, Nigeria, Mozambique, and Afghanistan. Brazil, in particular, is known for producing a wide variety of tourmaline colors, including the rare and valuable Paraíba tourmaline.
Gemological Properties
Opal
- Chemical Formula: SiO₂·nH₂O
- Crystal System: Amorphous
- Hardness (Mohs): 5–6.5
- Refractive Index: 1.34–1.59 (varies depending on the type)
- Luster: Vitreous to waxy
- Color: Opal can be found in a wide range of colors, from clear and white to black and vibrant multicolored patterns. The most valuable opals display a play of color, where different colors appear as the stone is moved.
- Cut: Typically cut as a cabochon to display its play of color.
- Clarity: Opal is generally opaque or translucent. The presence of inclusions or fractures can affect its value.
- Special Optical Effects: Play of color is the defining characteristic of precious opal. This effect occurs when light is diffracted by the microscopic silica spheres within the stone.
Opal is one of the few gemstones that can display multiple colors simultaneously, and the most valuable specimens are known as black opals, which have a dark body tone that enhances the contrast of the play of color.
Tourmaline
- Chemical Formula: Complex borosilicate mineral, often represented as XY₃Z₆(BO₃)₃(SiO₄)₃(O, OH, F)
- Crystal System: Trigonal (uniaxial)
- Hardness (Mohs): 7–7.5
- Refractive Index: Varies depending on the type, typically 1.62–1.64
- Luster: Vitreous
- Color: Tourmaline is known for its wide range of colors, including red, pink, green, blue, yellow, and black. Some stones display color zoning, where different colors appear in different sections of the crystal.
- Cut: Tourmaline is commonly faceted, and it can also be cut into cabochons or freeform shapes.
- Clarity: Tourmaline is often found with inclusions, which are generally considered acceptable and even desirable in some cases, as they can add character to the stone.
- Special Optical Effects: Tourmaline can exhibit pleochroism, meaning it appears different in color when viewed from different angles. Some varieties, like Paraíba tourmaline, display a vivid neon blue-green color that is highly sought after.
Tourmaline’s durability and hardness make it a popular choice for a wide range of jewelry, including rings, pendants, and earrings.
Symbolism and Metaphysical Beliefs
Opal
Opal has long been associated with hope, purity, and spiritual awakening. In ancient Roman times, opal was considered a symbol of hope and innocence, and it was believed to bring good fortune to its wearer. The gemstone was also thought to enhance love and passion, and it was often used in love charms and talismans.
In medieval Europe, opal was believed to have healing properties and was used in amulets to protect against illness and misfortune. Some cultures believed that opal could predict the future and that it was a stone of divine inspiration.
However, opal’s reputation was not always positive. In the 19th century, Sir Walter Scott’s novel Anne of Geierstein portrayed opal as a stone of bad luck, which led to a sharp decline in its popularity. This negative association lasted for several decades, but opal eventually regained its status as a beloved gemstone.
In modern metaphysical beliefs, opal is associated with emotional balance, creativity, and self-expression. It is believed to help the wearer see the beauty in life and to enhance intuition and insight. Some practitioners use opal in crystal healing to promote inner peace and emotional healing.
Tourmaline
Tourmaline is associated with a wide range of symbolic meanings, largely due to its diverse color palette. Different colors of tourmaline are believed to have different properties and energies.
Black tourmaline is one of the most popular varieties and is associated with protection, grounding, and energy cleansing. It is often used in spiritual practices to shield the wearer from negative energies and to promote a sense of inner strength and stability.
Pink tourmaline is believed to promote love, compassion, and emotional healing. It is often used in love spells and heart-centered meditations.
Green tourmaline is associated with abundance, prosperity, and vitality. It is believed to attract good luck and financial success.
Blue tourmaline is associated with calmness, clarity, and communication. It is often used to help the wearer speak their truth and to promote a sense of peace and understanding.
Red tourmaline is associated with passion, courage, and vitality. It is believed to enhance energy and motivation, and it is often used in fitness and performance practices.
In modern metaphysical practices, tourmaline is considered a versatile and powerful stone that can be used for a wide range of purposes. It is often used in chakra work, particularly for the root chakra, where it is believed to promote stability and grounding. It is also used in energy healing to clear blockages and restore balance.
Care and Cleaning
Proper care is essential to preserving the beauty and value of both opal and tourmaline. Each gemstone has different requirements due to its unique physical properties.
Opal
Opal is a relatively soft and porous gemstone, with a Mohs hardness of 5–6.5, making it more vulnerable to scratches and damage. It is also hygroscopic, meaning it can absorb and lose moisture, which can cause it to become cracked or dehydrated if not handled properly.
To care for opal jewelry:
- Avoid exposure to extreme heat or dry environments, such as direct sunlight or hot cars.
- Store opal separately from other gemstones to prevent scratches.
- Clean with a soft cloth and mild soap and water. Avoid using harsh chemicals or ultrasonic cleaners.
- Do not expose opal to sudden temperature changes, which can cause it to crack.
Opal is best suited for occasional wear rather than everyday use, particularly in rings or bracelets that are more likely to be subjected to impact.
Tourmaline
Tourmaline is much more durable than opal, with a Mohs hardness of 7–7.5, making it suitable for everyday wear in a variety of jewelry settings.
To care for tourmaline jewelry:
- Clean with a soft cloth and mild soap and water.
- Avoid exposure to high heat for extended periods, as tourmaline can be sensitive to thermal shock.
- Store tourmaline separately from softer gemstones to prevent scratches.
- Avoid using ultrasonic or steam cleaners, as they can damage the stone or loosen its setting.
Tourmaline is generally easy to maintain and is a practical choice for a wide range of jewelry, including rings, pendants, and earrings.
Conclusion
October’s dual birthstones—opal and tourmaline—are two of the most fascinating and versatile gemstones in the world of birthstones. Their unique geological properties, rich historical significance, and symbolic meanings make them highly valued in both traditional and modern contexts.
Opal, with its iridescent play of color, has been cherished for centuries for its beauty and spiritual significance. It is a symbol of hope and purity and is best suited for occasional wear due to its relative softness and porosity.
Tourmaline, on the other hand, is a hard and durable gemstone that comes in a wide range of colors, making it a versatile choice for jewelry. It is associated with a variety of metaphysical properties, from protection and grounding to love and prosperity, and it is well suited for everyday wear.
Together, these two gemstones reflect the diversity and richness of October’s birthstone tradition. Whether worn for aesthetic beauty, spiritual significance, or practical use, opal and tourmaline continue to captivate gemstone lovers around the world.