Opal is a gemstone defined by its extraordinary visual character, a play of color that has captivated humanity for centuries. It holds a unique and sometimes contradictory status in the world of birthstones, serving as a primary gem for October and a traditional, though less common, choice for May. Its composition, unlike most gemstones, is amorphous, leading to a suite of properties and lore that set it apart from its crystalline counterparts. This article explores the multifaceted nature of opal, drawing from its recognized place in popular culture, its historical associations with luck and misfortune, its scientific identity as hydrated silica, and its practical considerations for care and wear.
The Dual Birthstone Identity: May and October
The association of opal with specific months is not as straightforward as for many other gems, presenting a fascinating case of historical evolution and cultural divergence.
Opal as a May Birthstone
While modern lists in the United States primarily designate emerald as the birthstone for May, opal maintains a strong, albeit alternative, connection to this month. This link is particularly evident in popular culture and historical calendars. The provided sources highlight opal's appearance in crossword puzzles as a frequent clue for "May's birthstone," demonstrating a widespread public recognition of this association. One source notes the clue "Milky birthstone" as a direct answer for opal, while another connects the answer "Milky resource found in the outback" to the gem, reinforcing both its descriptive qualities and its primary source in Australia.
The connection to May also extends to older and different cultural systems. The old Hebrew calendar, for instance, listed carnelian (a variety of chalcedony, which is microcrystalline quartz) as a May birthstone, but also designated chalcedony itself. As opal is composed of silica, it exists in a broader mineralogical family with chalcedony. Furthermore, chrysoprase, a green variety of chalcedony and a modern addition to May's stones, was historically a zodiac stone for Gemini, which falls partly in May. This network of associations within the silica mineral group helps contextualize opal's historical place among May's gems. Another source mentions that sapphire was the birthstone for May in the old Tibetan calendar, further illustrating the global diversity of birthstone traditions. In these contexts, opal's role is one of a traditional or regional alternative rather than the primary, universally accepted gem.
The Predominance of Opal for October
The primary and most widely accepted birthstone for October is opal. The sources clarify that opal was the gem trade's original recognized birthstone for this month. Its position was so strong that when an alternative was proposed, it was added as a supplement rather than a replacement. In 1952, the Jewelry Industry Council suggested pink tourmaline be offered as an alternate stone. This change was subsequently approved by the American Gem Society and the National Retail Jewelers Council. This historical event created the dual-stone option available to those born in October today, with opal retaining its primary status.
The Lore of Luck and Misfortune
Few gemstones are as entwined with superstition as opal. A powerful narrative of both good and bad fortune surrounds it, largely stemming from its unique optical properties and a specific literary influence.
The "Cursed" Gemstone
A persistent superstition warns that it is bad luck to wear an opal if it is not one's birthstone. The provided sources indicate that this belief is not rooted in ancient history but likely originated in the early to middle 19th century. A compelling theory points to Sir Walter Scott's 1831 novel, Anne of Geierstein, as the catalyst. In the novel, the character Lady Hermione wears an opal that reflects her moods—shining red when she was angry, blue when she was sad, and green when she was happy. The gem ultimately loses its color and fades upon her death. The book's immense popularity is believed to have single-handedly damaged the opal's reputation, linking its characteristic play of color to volatility and misfortune.
This literary effect was so profound that it reportedly caused a crash in the European opal market. However, the sources also note a kernel of truth that may have lent the story an air of credibility. Opals are indeed unstable relative to many other gems. They are a form of hydrated silica and can, over time, deteriorate. This process, known as "crazing," involves the loss of water, causing the stone to become opaque, develop cracks, and lose its play of color, transforming it into a "colorless mass of a chalky silicon dioxide." This physical reality of potential degradation likely made the fictional account in Scott's novel more believable to the public.
A Symbol of Hope and Purity
Despite the curse narrative, opal has also been a symbol of positive attributes. Its dazzling array of colors has linked it to hope, innocence, and purity. In ancient Rome, it was considered a symbol of good fortune and hope, second only to emerald in value. The Romans believed it combined the beauty of all other gems. The ancient Greeks also held opal in high regard, believing it gave the owner the power of prophecy and protection from disease. For centuries, opal has been associated with creativity, inspiration, and the amplification of one's thoughts and emotions.
Geological Formation and Global Sources
Opal's formation is a geological rarity, and its primary sources are concentrated in a few key regions of the world.
The Science of Silica Gel
Opal is not a crystal like quartz or diamond. It is an amorphous solid, meaning it lacks a defined crystal structure. Its chemical composition is silicon dioxide (SiO₂), the same as quartz, but with a variable and significant amount of water (typically 3% to 21% by weight). Its formula is often written as SiO₂·nH₂O. Opal forms from a silica-rich gel that seeps into cracks and voids within rocks, such as volcanic ash and sedimentary rock. Over millions of years, this gel hardens and, under the right conditions of pressure and temperature, forms the precious gemstone.
The defining characteristic of precious opal, its "play-of-color," is a result of this formation process. The silica is composed of millions of microscopic spheres stacked in a grid-like pattern. When light enters the stone, it is diffracted by this regular array of spheres, breaking it into its spectral colors. The size of the spheres determines which colors are displayed; smaller spheres produce blues and violets, while larger spheres produce reds and oranges.
Mining Locations
The sources identify Australia as the world's foremost source of opal, particularly for the prized black opal from Lightning Ridge. This connection is explicitly made in the crossword clue "Milky resource found in the outback." Other famous Australian opal fields include Coober Pedy and Mintabie, known for their white opal. While Australia dominates the market, other significant sources exist around the world, including Ethiopia, Mexico (known for fire opal), and Brazil.
Gemological Properties and Varieties
Understanding opal's physical and optical properties is essential for appreciating its uniqueness and ensuring its proper care.
A Profile of Opal
Opal's properties are distinct from most colored gemstones due to its amorphous nature and high water content. The sources provide several key characteristics.
| Property | Description |
|---|---|
| Chemical Composition | Hydrated Silicon Dioxide (SiO₂·nH₂O) |
| Crystal System | Amorphous |
| Hardness (Mohs Scale) | 5.5 - 6.5 |
| Toughness | Poor (prone to breakage) |
| Cleavage | None |
| Luster | Vitreous to resinous; can exhibit an opalescent or pearly sheen |
| Special Characteristic | Play-of-color (in precious opal) |
The hardness of opal is relatively low compared to many popular gems. This, combined with its poor toughness, makes it susceptible to scratching and breakage. The sources explicitly group opal with emerald and zircon as gems "prone to breakage" and note that, along with pearl and turquoise, it has a "low hardness and are easily scratched." This inherent fragility is a critical consideration for jewelry use.
Varieties of Opal and Other May Gems
The term "opal" encompasses a range of appearances. While the sources do not detail specific varieties like boulder opal or fire opal, they do describe opal as having a "milky" and "iridescent" appearance. "Milky opal" refers to the translucent to opaque white or light-colored body tone, while "iridescent" points to the play-of-color.
The sources also list several other traditional and modern birthstones for May, many of which are varieties of the mineral chalcedony (microcrystalline quartz): * Chrysoprase: A new addition to the modern list, this green chalcedony is chosen to align with the green color theme of May, similar to emerald. * Carnelian: A red variety of chalcedony, listed as a May birthstone in the old Hebrew calendar. * Agate: A banded variety of chalcedony, a traditional May stone in Roman, Italian, Hebrew, and Hindu calendars. * Chalcedony: The white or bluish variety itself was designated as a May stone in the old Hebrew calendar. * Sapphire: Listed as the May birthstone in the old Tibetan calendar.
This variety underscores that the concept of a "birthstone" is not monolithic but has evolved across different cultures and time periods.
Symbolism and Metaphysical Beliefs
Beyond its physical beauty, opal is rich in symbolic meaning and is believed by many to possess metaphysical properties.
- Emotional Balance: Chrysoprase and chalcedony, both related to May, are believed to stabilize emotions, relieve depression, and bring emotional balance. Chrysoprase is specifically noted for helping to "stave off depression."
- Creativity and Inspiration: Opal is widely regarded as a stone of inspiration and creativity. It is thought to stimulate original thought and enhance imagination.
- Amplification: A common belief is that opal amplifies thoughts, feelings, and emotions. It is said to be a karmic stone, reflecting back the user's own energy.
- Protection and Hope: Historically, opal was seen as a protective talisman and a symbol of hope and purity.
- Passion and Desire: Carnelian, a red chalcedony and May birthstone, is believed to "strengthen passion and desire."
- Intelligence and Articulation: Agate is associated with enhancing intelligence and making the wearer more articulate.
Care and Cleaning
Given its unique composition and physical properties, opal requires specific care to maintain its beauty and integrity.
Handling and Wear
The sources provide clear guidance on opal's vulnerabilities. Its low hardness (5.5-6.5 on the Mohs scale) means it can be easily scratched by everyday objects, including dust. Its poor toughness makes it prone to chipping or breaking if subjected to impact. For these reasons, opal is not an ideal choice for rings that are worn daily, such as engagement rings, where it would be exposed to hard knocks and abrasive wear. It is better suited for pendants, earrings, and brooches, where the risk of impact is significantly lower.
Cleaning Methods
Cleaning opal requires a gentle approach. The high water content and potential for crazing mean that harsh chemicals, extreme temperatures, and ultrasonic cleaners should be strictly avoided.
- Safe Cleaning: The best method is to use warm, soapy water and a very soft brush or cloth. Gently wipe the stone to remove dirt and oils.
- Drying: After washing, pat the opal dry with a soft, lint-free cloth. Allow it to air dry completely before storing.
- Avoid: Do not use steam cleaners, ultrasonic cleaners, or harsh detergents. Avoid sudden changes in temperature and prolonged exposure to intense heat or direct sunlight, as this can cause the stone to lose water and become damaged.
Conclusion
Opal stands as a testament to the diversity and wonder of the mineral kingdom. Its status as a birthstone is complex, with a firm place in October and a historical, though more niche, connection to May. This duality is mirrored in its lore, which swings between a 19th-century curse and ancient symbols of hope and creativity. Scientifically, it is an anomaly—a non-crystalline, water-bearing gem whose signature play-of-color is a trick of light within a microscopic lattice of silica spheres. Its relative fragility, characterized by a low hardness and poor toughness, demands careful handling and thoughtful placement in jewelry. Ultimately, opal is more than just a gemstone; it is a geological marvel and a cultural icon, whose shifting colors continue to fascinate and inspire.