Opal, alongside tourmaline, holds the distinction of being the birthstone for October. Revered for its captivating “play-of-color,” this mineraloid has fascinated cultures for millennia, embodying notions of hope, purity, and creativity. While not as consistently rare as once believed due to significant Australian discoveries, the unique optical phenomenon that defines opal continues to make it a prized gemstone. This article will delve into the history, geological origins, gemological properties, symbolism, and care of this remarkable October birthstone, drawing solely from available sources.
History and Lore
The story of opal’s naming is somewhat ambiguous. Most sources agree the term originates from the Latin opalus, first recorded around 250 BC, but the root of opalus remains debated. Some scholars suggest a connection to the Ancient Greek opallios, meaning “to see a change in color,” aptly describing the gem’s defining characteristic. Others propose a link to the Sanskrit upala, translating to “precious stone.”
Ancient civilizations attributed various powers to opal. Ancient Greeks believed the stone bestowed the gift of prophecy and offered protection from disease. In contrast, Europeans historically viewed opal as a symbol of purity, hope, and truth, believing it embodied the virtues of all colored stones. Bedouins held a more dramatic belief, associating opal with lightning and claiming it fell from the sky during thunderstorms.
The tradition of assigning gemstones to specific months dates back to the biblical breastplate of Aaron, adorned with twelve gemstones representing the tribes of Israel. This practice evolved over time, with Josephus, a first-century Jewish historian, linking these stones to both months and zodiac signs. The modern standardization of birthstones occurred in 1912 by the National Association of Jewelers (now Jewelers of America), solidifying opal’s place as a primary October birthstone. Opal is also traditionally given to celebrate the 14th wedding anniversary.
Geological Formation and Sources
Opal is unique in that it is not a true crystal but a mineraloid – an amorphous solid with a defined chemical composition. It forms from the gradual natural heating of silica gel found within cracks in rocks. The defining characteristic of precious opal, which constitutes approximately 5% of all opals, is its ability to exhibit “play-of-color” when exposed to white light. This phenomenon arises from the arrangement of microscopic spheres of silica, with water present between them. The size of these spheres dictates the range of colors displayed.
Historically, India served as the primary source of opals introduced to the Western world. However, Australia now dominates global opal production. Significant deposits are also found in Mexico, Ethiopia, and Brazil. Additional, though less prolific, opal occurrences have been identified in Honduras, Indonesia, Madagascar, Central Europe, Turkey, Peru, and the United States.
Gemological Properties
The most striking feature of opal is its play-of-color, a visual effect caused by the diffraction of light within the gemstone. This iridescence presents as flashes of various jewel tones, creating a dynamic and captivating appearance. Opals come in a range of colors, including black (the rarest and most valuable), gray, green, and white, and can even be colorless.
While the provided sources do not detail specific chemical formulas or refractive indices, they emphasize the gem’s composition of silica spheres and water. The arrangement of these spheres is crucial to the play-of-color effect. The sources do not provide information on opal’s hardness on the Mohs scale, cleavage, or specific gravity.
Symbolism and Metaphysical Beliefs
Throughout history, opal has been imbued with symbolic meaning. As previously mentioned, ancient cultures associated it with prophecy, protection, and purity. Modern interpretations continue to emphasize opal’s positive attributes. It is often believed to bring confidence and hope to the wearer, making it a meaningful gift for those born in October.
Contemporary metaphysical beliefs suggest opal protects against negative energy and enhances creativity. Some believe it fosters emotional balance and encourages individuality. The varied colors within an opal are also thought to represent different facets of its symbolism, offering a unique and personal connection to the stone.
Care and Cleaning
The sources do not provide detailed care instructions for opal. However, given its composition of silica and water, it is reasonable to infer that opal may be susceptible to damage from extreme temperatures or prolonged exposure to dryness. The sources mention that opal was sometimes considered too delicate for everyday use, leading to tourmaline being offered as a more durable alternative. Further research beyond the provided sources would be necessary to provide comprehensive care guidelines.
October’s Dual Birthstone Designation
The designation of two birthstones for October – opal and tourmaline – stems from a practical consideration. Historically, opal was perceived as a relatively delicate gemstone. To provide those born in October with a more durable and versatile option, tourmaline was added to the list, expanding the choices available. This dual designation reflects a desire to cater to diverse preferences and practical needs.
Conclusion
Opal remains a captivating and historically significant gemstone. From its debated origins to its mesmerizing play-of-color, it continues to inspire awe and wonder. As the traditional birthstone for October, it symbolizes hope, purity, and creativity, offering a unique and meaningful connection to those born during this month. While the provided sources offer a foundational understanding of opal, further research would be beneficial to fully appreciate its complex gemological properties and nuanced cultural history.