For those born on October 28th, the birthstone tradition assigns a unique duality, linking them to two remarkable gemstones: opal and tourmaline. These stones, though distinct in appearance and origin, share a common thread in their symbolic meanings—opal representing hope and tourmaline symbolizing stability and emotional balance. This duality reflects the richness of gemstone lore and the evolving nature of birthstone traditions. This article delves into the historical, geological, and cultural significance of these two gemstones, exploring their enduring appeal and their roles in the world of jewelry and gemology.
History and Lore
Opal: A Stone of Ancient Reverence
Opal has been cherished for thousands of years, with its name derived from the Sanskrit word “upala,” meaning “precious stone.” The ancient Romans later adapted this term to “opalus,” which evolved into the English “opal.” The earliest known opals were brought to the Western world from India, but significant deposits were later discovered in regions such as Australia, which now accounts for the majority of the world's opal production.
Throughout history, opal has been regarded with a mixture of awe and superstition. The ancient Greeks believed that opals granted the gift of prophecy and protection from disease. In medieval Europe, opal was associated with purity, hope, and truth. However, some cultures feared the stone, believing it to be a symbol of bad luck. Despite these varied beliefs, opal has remained a popular gemstone, especially in the 19th and 20th centuries, when its iridescent beauty captivated jewelers and collectors alike.
In the early 20th century, opal was designated as the official October birthstone. Its ethereal play-of-color—created by the diffraction of light within the stone—was seen as a metaphor for the many facets of human emotion and experience. Opal is also the stone given to celebrate the 14th wedding anniversary.
Tourmaline: A Stone of Stability and Diversity
Tourmaline, a relatively recent addition to the October birthstone list, represents the modern evolution of gemstone traditions. Known for its wide range of colors—often referred to as the “jewel of the rainbow”—tourmaline is a versatile and expressive gemstone. The name “tourmaline” is thought to derive from the Singhalese word “turmali,” meaning “mixed stones,” a reference to the variety of colors and forms the gemstone can take.
Tourmaline has been used in jewelry for centuries, though it was not officially recognized as a birthstone until the 20th century. Its inclusion alongside opal for October 28th reflects the gemstone's role in balancing the emotional and spiritual aspects of life. In metaphysical traditions, tourmaline is believed to promote emotional stability and grounding, making it a fitting companion to opal’s symbolic hope.
Geological Formation and Sources
Opal: A Unique and Iridescent Gemstone
Opal is a hydrated amorphous form of silica (SiO₂·nH₂O), meaning it lacks a definite crystalline structure. It is formed when water carrying dissolved silica seeps into the spaces of sedimentary rock and evaporates, leaving behind a network of tiny silica spheres. The way these spheres are arranged determines the play-of-color, the phenomenon that makes opal so visually striking.
The most significant source of opal is Australia, which produces over 90% of the world’s opal. Deposits are also found in Ethiopia, Mexico, and Brazil. In Ethiopia’s Shewa Province, for example, miners extract black opal and crystal opal from steep cliffs. In Mexico’s Querétero state, fire opal—known for its yellow, orange, and red hues—is a notable product of the region.
Tourmaline: A Diverse Silicate Mineral
Tourmaline is a complex borosilicate mineral that forms in a variety of geological environments, including igneous and metamorphic rocks. Its wide range of colors is due to trace elements such as iron, magnesium, and manganese, which influence the gemstone’s hue. The most famous varieties include black tourmaline (schorl), pink tourmaline (rubellite), and green tourmaline (verdelite).
Tourmaline is found in numerous countries around the world, with significant deposits in Brazil, Afghanistan, Nigeria, and the United States. Brazil, in particular, is known for producing high-quality tourmaline in a vast array of colors. The gemstone’s formation in pegmatite deposits—coarse-grained igneous rocks—contributes to its clarity and brilliance.
Gemological Properties
Opal
- Chemical Composition: Hydrated amorphous silica (SiO₂·nH₂O)
- Hardness (Mohs Scale): 5 to 6.5
- Luster: Vitreous to waxy
- Color: Opal can appear in a wide range of colors, but it is best known for its play-of-color, an optical phenomenon that displays a shimmering spectrum of colors when viewed from different angles.
- Transparency: Translucent to opaque
- Specific Gravity: 1.90 to 2.30
- Refractive Index: Varies depending on the type of opal
- Cleavage: None
- Fracture: Uneven to conchoidal
Tourmaline
- Chemical Composition: Borosilicate mineral with a complex formula that varies depending on the type of tourmaline (e.g., schorl: NaFe₃Al₆(Si₆O₁₈)(BO₃)₃(OH)₃O)
- Hardness (Mohs Scale): 7 to 7.5
- Luster: Vitreous
- Color: Available in nearly every color of the rainbow, including black, green, pink, blue, and yellow
- Transparency: Transparent to translucent
- Specific Gravity: 3.00 to 3.25
- Refractive Index: 1.62 to 1.64
- Cleavage: Poor in one direction
- Fracture: Conchoidal
| Gemstone | Hardness (Mohs) | Color Range | Luster | Transparency | Refractive Index |
|---|---|---|---|---|---|
| Opal | 5–6.5 | White, yellow, orange, red, and with play-of-color | Vitreous to waxy | Translucent to opaque | Varies |
| Tourmaline | 7–7.5 | Black, green, pink, blue, yellow, and more | Vitreous | Transparent to translucent | 1.62–1.64 |
Symbolism and Metaphysical Beliefs
Opal
Opal has long been associated with hope, inspiration, and the ability to see the many facets of life. In ancient Greece, it was believed to grant the power of prophecy and protection from disease. During the Middle Ages, opal was considered a symbol of purity, hope, and truth. However, in some European cultures, opal was also regarded as an omen of bad luck, particularly if it was not the first gemstone the wearer encountered.
In modern metaphysical traditions, opal is believed to enhance creativity, emotional balance, and spiritual insight. It is said to help individuals connect with their inner selves and embrace the full spectrum of their emotions. Opal is also associated with the throat chakra, which governs communication and self-expression.
Tourmaline
Tourmaline is known for its grounding and stabilizing properties. Different colors of tourmaline are believed to have different effects. For example:
- Black tourmaline (schorl): Known as a powerful protective stone, it is believed to absorb negative energy and promote emotional stability.
- Pink tourmaline (rubellite): Associated with love, compassion, and emotional healing.
- Green tourmaline (verdelite): Linked to growth, abundance, and a connection to nature.
Tourmaline is also believed to help with physical ailments, particularly those related to the endocrine system and the spine. It is considered a versatile and powerful gemstone, making it a popular choice for those seeking balance and harmony in their lives.
Care and Cleaning
Opal
Opal requires careful handling due to its relatively low hardness and sensitivity to water and heat. It is recommended to clean opal with warm, soapy water and a soft cloth. Avoid using ultrasonic or steam cleaners, as these can cause the stone to lose water content and crack.
Opal should also be stored separately from harder gemstones to prevent scratches. Prolonged exposure to water can weaken the adhesive in opal doublets and triplets, so it is best to avoid soaking these stones. Opal should not be exposed to high heat or sudden temperature changes, as this can cause it to fracture.
Tourmaline
Tourmaline is more durable than opal, with a higher hardness on the Mohs scale. It can be cleaned with warm, soapy water or a mild jewelry cleaner. Ultrasonic and steam cleaners are also generally safe for tourmaline, although it is advisable to check for any inclusions or treatments that may be sensitive.
Tourmaline should be stored in a dry place, away from other abrasive gemstones. It is also recommended to avoid exposing tourmaline to extreme heat, as some varieties may contain iron, which can cause discoloration.
Conclusion
The dual birthstones for October 28th—opal and tourmaline—represent a fascinating blend of history, geology, and symbolism. Opal, with its iridescent play-of-color and ancient associations with hope and prophecy, continues to captivate gemstone enthusiasts. Tourmaline, with its diverse range of colors and grounding properties, complements opal’s ethereal beauty with a sense of stability and balance.
These gemstones not only serve as beautiful adornments but also carry deep cultural and metaphysical significance. Whether worn for their aesthetic appeal or their symbolic meanings, opal and tourmaline remain treasured stones in the world of birthstones and jewelry.