Opal, the traditional birthstone for October, is a gemstone celebrated for its captivating play-of-color and rich history. While tourmaline was added as a secondary birthstone in 1912, opal remains the most widely recognized gem associated with this month. Valued for centuries across diverse cultures, opal’s origins are traced back to India, where it was known as upala, meaning “precious stone.” This article will delve into the history, geological formation, gemological properties, and cultural significance of this remarkable gemstone.
History and Lore
The story of opal is interwoven with tales of hope, love, and even supernatural power. Ancient Romans referred to opal as opalu, a term derived from the Sanskrit upala. Throughout history, different civilizations have attributed unique meanings to the stone. Ancient Greeks believed opal bestowed the gift of prophecy and offered protection from disease. In Europe, opal long symbolized purity, hope, and truth, and was once thought to embody the virtues of all colored stones.
Bedouin tribes held the belief that opal contained lightning and descended from the sky during thunderstorms. Aztec civilizations associated the stone with necessary destruction for new creation. During the Middle Ages, opal was considered a lucky stone, while in Victorian times, Queen Victoria was a noted collector and admirer of opals. Ancient Romans associated the gem with hope and love. These varied beliefs demonstrate the enduring fascination with opal’s unique beauty and perceived powers.
Geological Formation and Sources
The formation of opal is a complex process that continues to be studied by scientists. While a definitive explanation remains elusive, the most prevalent theory suggests that opal forms when water flows through the earth, dissolving silica from sandstone. As this silica-rich water travels, it deposits silica in crevices and voids. Over time, changes in acidity and evaporation lead to the formation of opal.
Alternative theories include the Syntectonic Model, which proposes that silica-rich groundwater is pushed up through the Earth’s surface, and the Microbe Model, credited to Dr. Hans-Jurgen Behr. This model suggests that opal formation involves a combination of bacteria, enzymes, and acids from the soil, supported by the discovery of fossils within some opal stones.
Unlike many gemstones that form as crystals, opal is formed as a “lump,” a non-crystalline structure.
Australia is the world’s most abundant source of opal, particularly the rare black opal found in Lightning Ridge, a small town in New South Wales. Significant opal deposits are also found in Ethiopia, Mexico, and Brazil. Other locations where opal has been discovered include the United States, Central Europe, Honduras, Indonesia, Madagascar, Peru, and Turkey.
Gemological Properties
Opal is a unique gemstone distinguished by its “play-of-color,” the shifting rainbow hues that characterize precious opal. This phenomenon is what sets it apart from common opal, which lacks this vibrant display. The play-of-color has been likened to fireworks, galaxies, and volcanoes, inspiring awe and wonder for centuries.
On the Mohs hardness scale, opal ranks between 5.5 and 6.5, making it relatively softer than many other gemstones. This means it requires careful handling and protection from scratches and abrasions. Opal is composed of hydrated amorphous silica, with a variable water content that can range from 3% to 21%.
Opal is classified into two broad categories: precious and common. Precious opal exhibits play-of-color, while common opal does not. Within precious opal, there are several varieties, including white opal, black opal, fire opal, and crystal opal. Black opal, prized for its dark body tone, is the rarest and most valuable type.
Symbolism and Metaphysical Beliefs
Throughout history, opal has been imbued with symbolic meaning. Ancient cultures believed it held protective powers and could bestow prophetic abilities. In the context of modern birthstone symbolism, opal is associated with hope, purity, and truth. It is also the traditional gemstone given to celebrate the 14th wedding anniversary.
While not scientifically verifiable, some modern sources suggest that opal promotes emotional healing and encourages individuality. It is believed to stimulate creativity and inspire a sense of wonder. These metaphysical beliefs contribute to opal’s enduring appeal and its continued use in jewelry and spiritual practices.
Care and Cleaning
Due to its relatively low hardness, opal requires special care to maintain its beauty. It is susceptible to scratches and can be damaged by harsh chemicals or extreme temperatures. To clean opal jewelry, it is best to use a soft cloth and lukewarm soapy water. Avoid ultrasonic cleaners and steam cleaners, as these can cause damage.
Opal is also sensitive to dehydration. Prolonged exposure to dry air can cause the stone to crack or become dull. To prevent this, it is recommended to occasionally immerse opal jewelry in water for a short period. Storing opal jewelry separately from other gemstones will help prevent scratches.
Conclusion
Opal, the captivating birthstone of October, is a gemstone steeped in history, lore, and geological intrigue. From its ancient origins in India to its modern-day appreciation for its unique play-of-color, opal continues to fascinate and inspire. Its delicate nature requires careful handling, but the rewards – a shimmering display of rainbow hues and a connection to centuries of cultural significance – are well worth the effort. Whether admired for its beauty, cherished for its symbolic meaning, or simply enjoyed as a stunning piece of jewelry, opal remains a truly exceptional gemstone.