Opal, designated as the primary birthstone for October, is a gemstone celebrated for its captivating “play-of-color”—a mesmerizing display of iridescent hues. Often referred to as the “Queen of Gemstones,” opal holds a unique position in the world of precious stones, admired for its beauty and steeped in history and lore. This article will delve into the origins, geological formation, gemological properties, historical significance, and care of this remarkable gemstone, drawing exclusively from available sources.
History and Lore
The story of opal’s name is somewhat ambiguous, with origins potentially tracing back to the Sanskrit word upala, meaning “precious stone,” or the Latin opalus, first recorded in 250 BC. Some interpretations suggest a connection to the Ancient Greek opallios, meaning “to see a change in color,” aptly describing the gem’s defining characteristic. Ancient Romans considered opal a symbol of hope and love, giving it the name opalus, meaning “precious stone.”
Throughout history, opal has been imbued with diverse meanings. Ancient Greeks believed it bestowed the gift of prophecy and protection from disease. Europeans long regarded it as a symbol of purity, hope, and truth, and for centuries, it was thought to embody the virtues of all colored stones. Bedouins once believed opal held lightning and fell from the sky during thunderstorms.
However, a superstition arose in the 19th century, popularized by Sir Walter Scott in his novel Anne of Geierstein, suggesting that wearing an opal brought bad luck unless it was one’s birthstone. The novel depicted an opal changing color with the moods of its wearer and losing its brilliance upon her death, contributing to the gem’s temporary decline in popularity. This superstition is considered a relatively recent development, not deeply rooted in historical belief.
Geological Formation and Sources
Opal is unique in that it is not a crystalline gemstone but rather a mineraloid—a substance with a mineral-like structure but lacking a defined crystalline form. It forms from the gradual natural heating of silica gel found in the cracks and crevices of rocks. Seasonal rains play a crucial role in its creation; rainwater carrying dissolved silica seeps into the ground, particularly in arid regions. As the water evaporates, these silica deposits are left behind, slowly accumulating over time to form opal.
Australia is by far the most significant source of opal globally, yielding the most abundant supplies. However, opal can also be found in Ethiopia, Mexico, and Brazil. Deposits have also been discovered in the United States, Central Europe, Honduras, Indonesia, Madagascar, Peru, and Turkey.
Gemological Properties
Opal typically ranges from 5 to 6.5 on the Mohs scale of hardness, making it relatively softer than many other gemstones. This softness makes it susceptible to scratches and abrasions, requiring careful handling and storage. Opal’s composition is characterized by a hydrated amorphous form of silica (SiO2), often containing between 3% and 30% water. This high water content contributes to its sensitivity to temperature changes and prolonged exposure to dryness.
Opals are broadly classified into two categories: precious and common. The key distinction lies in the presence of “play-of-color,” the iridescent display of rainbow hues. Precious opal exhibits this phenomenon, while common opal does not. This play-of-color is caused by the diffraction of light as it passes through microscopic spheres of silica within the stone.
Opal doublets and triplets are also common. Doublets consist of a thin slice of opal glued to a base material, while triplets feature a slice of opal sandwiched between two layers of clear quartz. These constructions enhance the appearance of the opal and provide added durability.
Symbolism and Metaphysical Beliefs
Opal is traditionally associated with hope, purity, and truth. It is believed to bring confidence and inspire artistic expression, owing to its diverse and captivating color palette. Historically, it was credited with numerous supernatural origins and powers, and was thought to bestow good luck upon its wearer. As the birthstone for October, it is considered to symbolize happiness and love, strengthening relationships for those born in that month.
Care and Cleaning
Due to its relatively soft nature and high water content, opal requires specific care to maintain its beauty. Prolonged exposure to heat or sudden temperature changes can cause cracking and scratching. It is also porous and susceptible to damage from detergents and harsh chemicals.
The safest method for cleaning opal is with warm, soapy water. However, the cleaning process should be brief, and prolonged immersion in water should be avoided, particularly for opal doublets and triplets, as it can weaken the adhesive binding the layers together.
To prevent scratching, opal should be stored separately from harder gemstones like diamonds, rubies, sapphires, and emeralds. Maintaining a slightly humid environment can also help prevent the opal from drying out and cracking. Adding a soaked cotton ball to a jewelry box can help achieve this. Opal that has been treated with oil, wax, or plastic requires particularly gentle cleaning to avoid removing the treatment.
Conclusion
Opal remains a captivating and historically significant gemstone. Its unique play-of-color, combined with its rich history and symbolic associations, continues to fascinate and inspire. While its relative softness and sensitivity to environmental factors require careful handling, the beauty and allure of opal ensure its enduring appeal as a prized possession and the cherished birthstone of October.