Opal, the traditional birthstone for October, is a gemstone unlike any other. Its defining characteristic, known as play-of-color, is a breathtaking display of iridescent flashes that seem to dance and shift within the stone. This captivating phenomenon, combined with its rich history and diverse symbolism, has made opal one of the most revered and storied gemstones in the world. For those born in the tenth month, opal offers a personal connection to a stone that embodies both the wonders of nature and the depth of human culture. This article explores the multifaceted world of opal, from its geological formation and global sources to its gemological properties, historical lore, and practical care.
History and Lore
The history of opal is steeped in myth, legend, and shifting perceptions. The very name of the stone is believed to have ancient roots. According to multiple sources, the word "opal" is thought to originate from the Sanskrit word upala, meaning "precious stone." This term was later adapted into Greek as opallios, which translates to "to see a change in color"—a fitting description for a stone renowned for its dynamic play-of-color. In ancient Rome, the name evolved into opalus, and the stone was held in exceptionally high regard. Roman writers noted that opal was considered second only to the emerald in value, and Roman Caesars frequently gifted opals to their wives, believing the stone would bring them good fortune.
This perception of opal as a bringer of good luck and protection was widespread in the ancient world. The ancient Greeks believed that opal bestowed the gift of prophecy and offered protection from disease. In Bedouin folklore, a mystical belief held that opal contained lightning and was formed when it fell from the sky during thunderstorms. Over time, opal came to be seen as a symbol of hope, purity, and truth, particularly in European cultures. Its ability to display the colors of all other gems led to the belief that it embodied the virtues and powers of every colored stone.
However, opal’s reputation experienced a dramatic reversal in more recent centuries. A persistent superstition suggests that it is bad luck to wear an opal if it is not one’s birthstone. This belief, however, is not rooted in ancient history. Sources indicate it likely emerged in the early or middle 19th century. One theory attributes its popularization to Sir Walter Scott’s 1831 novel, Anne of Geierstein. In the story, a character possesses an opal that reflects her moods with changing colors and loses its vibrancy upon her death. This narrative may have inadvertently reinforced the idea of opal as an unstable or unlucky stone. In reality, the story’s observation may have been based on a geological fact: opals can deteriorate over time, changing from a vibrant, glassy gem to a colorless, chalky mass of silicon dioxide as they pass through an unstable phase on their journey to becoming crystalline quartz.
Despite this period of superstition, opal’s intrinsic beauty and historical significance endured. Its journey to becoming a modern birthstone was formalized in the early 20th century. By 1912, opal was officially recognized as the primary birthstone for October. Later, in 1952, the Jewelry Industry Council suggested the addition of an alternative birthstone to provide more options. This was accepted and approved by the American Gem Society and the National Retail Jewelers Council, solidifying opal’s status alongside its companion stone, tourmaline. Today, opal is also traditionally given to celebrate the 14th wedding anniversary.
Geological Formation and Sources
Opal is a unique gemstone in the mineral kingdom. Unlike most gemstones, which are crystalline, opal is amorphous. It is a form of hydrated silica, with the chemical formula often represented as SiO₂·nH₂O. This means it is composed of silicon dioxide (the same material as quartz) but with a variable amount of water integrated into its structure. The gem forms when silica-rich water seeps into cracks and cavities in rocks. As the water evaporates, it leaves behind deposits of silica spheres, which stack together in a grid-like pattern. It is the size and regularity of these spheres that create opal’s signature play-of-color. Light passing through these microscopic spheres diffracts, breaking into the spectral colors of the rainbow.
Opal can be categorized into two main types: precious opal, which displays play-of-color, and common opal, which does not. The sources of precious opal are geographically concentrated, with Australia being the most significant producer globally. The fields of New South Wales, South Australia, and Queensland, discovered in the late 19th century, remain the primary sources of the world’s opal. These Australian mines yield a wide variety of opals, including the prized black opal with its dark body color that makes the play-of-color exceptionally vivid.
In recent decades, other important sources have emerged. Ethiopia has become a key producer, with mines in regions like Wollo yielding opals with body colors ranging from white, yellow, and orange to brownish-red and even "chocolate" brown, some of which exhibit strong play-of-color. Another mine in Ethiopia’s Shewa Province is noted for producing coveted black opal, as well as orange, white, and crystal opal. Mexico is renowned for its fire opal, typically found in shades of yellow, orange, and reddish-orange to red, with some varieties showing good play-of-color. The mines in Querétaro, for instance, are known destinations, though reaching them requires navigating challenging terrain.
Other notable sources include Brazil, Guatemala, and Honduras. Historically, Old World sources included Czechoslovakia and Hungary, which were important before the major Australian discoveries. This global distribution means that while Australia remains the powerhouse of opal production, the gemstone can be found in many parts of the world, each region offering stones with distinct characteristics.
Gemological Properties
Opal’s physical and optical properties make it a distinctive and sometimes challenging gem for jewelers and wearers. Its most celebrated feature is its play-of-color, which can display flashes of blue, green, orange, and red across the visible spectrum. The quality of this phenomenon is judged by the intensity, distribution, and size of the color flashes. The finest opals have an even distribution of colors in fairly large splotches; pinpoints of light are considered less desirable. Gray or brown undertones in the body color can detract from the stone’s value.
Color and Body Tone: The base color of opal, known as body color, can vary widely. Traditionally, opals are classified as black or white, but other base hues include red, purple, and orange. The body color is influenced by the presence of certain chemical impurities. Black opal, with a dark body tone, is the most valuable due to the dramatic contrast it provides for the play-of-color. White opal, or light opal, has a light or white body color. Fire opal is prized for its warm, transparent body color, which can range from yellow to red, and may or may not show play-of-color.
Hardness and Durability: On the Mohs scale of hardness, opal ranges from 5 to 6.5. This places it in the mid-range, making it softer than many other popular gemstones like quartz (7) or sapphire (9). This relative softness means opal is susceptible to scratching and abrasion. Furthermore, opal is not very tough; it has a conchoidal to splintery fracture and can be brittle. It is also sensitive to sudden temperature changes and prolonged exposure to water, which can cause it to crack or craze. These properties necessitate careful handling and appropriate jewelry settings.
Clarity and Structure: Solid opal is the most highly preferred form. However, the play-of-color is often confined to thin layers of horizontally banded opal. To enhance durability and appearance, opal is frequently fashioned into doublets or triplets. A doublet consists of a thin slice of opal glued to a base material (often black onyx or ironstone) and covered with a thin dome of clear quartz. A triplet adds another layer, with a colored back beneath the opal slice. These composite stones account for many opals in the market, as they provide a larger, more stable gem at a lower cost. Some opals may also exhibit chatoyancy, producing a fine eye-like reflection, which is desirable even when play-of-color is insignificant.
| Property | Description |
|---|---|
| Chemical Formula | SiO₂·nH₂O (Hydrated Silicon Dioxide) |
| Crystal System | Amorphous |
| Hardness (Mohs) | 5 - 6.5 |
| Refractive Index | ~1.45 (variable) |
| Specific Gravity | ~2.15 (variable) |
| Key Feature | Play-of-color (iridescence) |
| Common Treatments | Impregnation (oil, wax, plastic), Doublets/Triplets |
| Common Origins | Australia, Ethiopia, Mexico, Brazil |
Symbolism and Metaphysical Beliefs
Beyond its geological and gemological attributes, opal is rich in symbolism and has been attributed with various metaphysical powers throughout history. In ancient cultures, including Hindu, Greek, and Roman societies, opal was highly regarded for its perceived powers of foresight. It was seen as a talisman and amulet, symbolizing ever-changing fortune and healing powers.
The stone’s meaning is deeply connected to its visual nature. Its ability to reflect a multitude of colors has led it to symbolize confidence, loyalty, hope, purity, happiness, and faithfulness. These positive concepts add an extra layer of personal meaning for those who wear it.
In the realm of holistic or alternative beliefs, opal is said to possess healing properties. Historically, it was believed to be able to heal various diseases, including eye disease, and to ward off evil, keeping the wearer safe. Some modern sources suggest it can help estranged family members find their way home for reconciliation. For business people and travelers, opal is admired and considered a safe traveling charm. It is also believed to give the wearer an understanding of higher powers. While these metaphysical beliefs are not supported by scientific gemology, they remain an important part of opal’s cultural legacy and appeal to many enthusiasts.
Care and Cleaning
Due to its unique composition and physical properties, opal requires specific care to maintain its beauty and integrity. The primary rule is to protect it from harsh conditions and chemicals.
Cleaning: The safest method for cleaning opal jewelry is with warm, soapy water and a soft brush. It is crucial to avoid ultrasonic cleaners, steam cleaners, and harsh chemicals, as these can damage the stone or the adhesive used in doublets and triplets. For doublets and triplets, prolonged exposure to water should be avoided, as it can weaken the glue holding the layers together. After washing, the jewelry should be dried thoroughly with a soft, lint-free cloth.
Storage: Because opal is relatively soft (5-6.5 on the Mohs scale), it can be easily scratched by harder gems. Therefore, it should be stored separately from other jewelry, ideally in a soft pouch or a lined jewelry box. This prevents contact with diamonds, sapphires, rubies, and even other opals that might have sharper edges.
Handling and Environment: Opal is sensitive to sudden temperature changes and high heat, which can cause fractures or crazing (a network of fine cracks). It should not be exposed to direct, intense sunlight or high-temperature environments for extended periods. When wearing opal jewelry, it is wise to remove it during activities that could subject it to physical impact, such as gardening, sports, or heavy housework. For rings or pieces that will make frequent contact with solid objects, opal doublets or triplets are often recommended for their enhanced durability.
Conclusion
Opal remains a gemstone of unparalleled allure, captivating observers with its internal play-of-color that mimics a miniature universe. As the traditional birthstone for October, it carries a legacy that spans from ancient Sanskrit roots to modern jewelry settings. Its journey through history is marked by reverence, superstition, and a lasting appreciation for its natural beauty. Geologically, it is a testament to the slow, patient processes of nature, forming from silica-rich waters in specific regions of the world, with Australia, Ethiopia, and Mexico standing out as key sources. Its gemological profile, characterized by moderate hardness, brittleness, and a unique amorphous structure, dictates careful handling and specialized cleaning methods. Whether valued for its historical symbolism of hope and protection, its metaphysical associations with healing and travel, or simply its stunning visual spectacle, opal continues to be a cherished stone. For the October-born individual, it offers a personal connection to a gem that is as dynamic and multifaceted as life itself.