Opal, celebrated as one of the birthstones of October alongside tourmaline, holds a captivating place in the world of gemstones. Revered for its unique “play-of-color,” a mesmerizing display of shifting rainbow hues, opal has inspired awe and attributed with diverse meanings throughout history. This article delves into the origins, geological formation, historical significance, and gemological properties of this enchanting gemstone.
History and Lore
The story of opal’s name is somewhat ambiguous. While most accounts trace its origin to the Latin word opalus, first recorded around 250 BC, the root of this term 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 the Sanskrit word upala, meaning “precious stone,” as a more likely source.
Ancient civilizations imbued opal with rich symbolism. In India, where the first opals were imported into the West, the stone was known as Upala and considered a precious gem. Ancient Romans associated opal with hope and love, giving it the name opalus. The Bedouin tribes believed opals contained lightning and fell from the sky during thunderstorms. Ancient Greeks attributed prophetic gifts and protection from disease to the stone. In Europe, opal became a symbol of purity, hope, and truth, believed to embody the virtues of all colored stones.
Despite its long history of positive associations, a superstition arose in the 19th century suggesting that wearing an opal was unlucky if it wasn’t one’s birthstone. This belief is often attributed to Sir Walter Scott’s 1831 novel, Anne of Geierstein, where an opal’s changing colors mirrored the moods of a character, ultimately fading with her death. This narrative, though fictional, contributed to a temporary decline in opal’s popularity. Opal is also traditionally given as a gift to celebrate the 14th wedding anniversary.
Geological Formation and Sources
Opal is unique among gemstones as it is a mineraloid, rather than a true mineral. It is formed by the gradual natural heating of silica gel found in the cracks and crevices of rocks. This silica-rich solution, carried by seasonal rains, seeped into ancient rock formations, particularly in areas with dry ground. As the water evaporated, deposits of silica were left behind, slowly solidifying into opal over extended periods.
While opal can be found in various locations worldwide, Australia is by far the most significant source, yielding the majority of the world’s supply. Other notable sources include Ethiopia, Mexico, and Brazil. Deposits have also been discovered in the United States, Central Europe, Honduras, Indonesia, Madagascar, Peru, and Turkey.
Opals are broadly classified into two categories: precious and common. The distinction lies in the presence of “play-of-color,” the iridescent display of rainbow hues that characterizes precious opal. Common opal lacks this effect.
Gemological Properties
Opal’s composition is primarily hydrated amorphous silica (SiO2·nH2O), meaning it contains water within its structure. This water content contributes to its relative softness and susceptibility to damage from heat or dehydration. On the Mohs hardness scale, opal ranks between 5.5 and 6.5, making it more fragile than many other gemstones.
The defining characteristic of precious opal is its “play-of-color,” caused by the diffraction of light through microscopic spheres of silica within the stone. The size and arrangement of these spheres determine the colors observed. Different types of opal exhibit different play-of-color patterns, including harlequin (patchwork), floral, pinfire, and broadflash.
While opal comes in a variety of colors, including white, black, and crystal, it is the play-of-color that determines its value. Black opal, with a dark body tone, is generally the most valuable, as it provides a striking contrast for the play-of-color.
Symbolism and Metaphysical Beliefs
Throughout history, opal has been associated with a range of symbolic meanings and metaphysical properties. Ancient cultures believed it possessed the power to bestow prophetic visions and protect against disease. It was considered a stone of hope, purity, and truth. Some believed that opals contained the virtues and powers of all colored stones.
More recently, opal has been linked to confidence and hope, making it a meaningful gift for those born in October. It has also been credited with numerous supernatural origins and powers, though these claims are not substantiated by scientific evidence.
Care and Cleaning
Due to its relatively low hardness and water content, opal requires careful handling and maintenance. It is susceptible to scratching, chipping, and cracking, particularly from sudden temperature changes or exposure to high heat.
The safest way to clean opal jewelry is with warm, soapy water and a soft cloth. Avoid harsh chemicals, ultrasonic cleaners, and steam cleaners, as these can damage the stone. It is also advisable to avoid prolonged exposure to sunlight or heat, as this can cause the opal to lose its color and become brittle.
Interesting Facts
The most expensive opal in the world, known as “Virgin Rainbow,” is valued at $750,000 per gram. Opal is not only the birthstone for October but also the traditional gemstone for the 14th wedding anniversary. The stone’s reputation for being unlucky is a relatively recent phenomenon, stemming from a 19th-century novel.
Conclusion
Opal remains a captivating and cherished gemstone, prized for its unique play-of-color, rich history, and symbolic significance. From its ancient origins in India to its modern status as a beloved birthstone, opal continues to inspire awe and wonder. Its delicate nature requires careful handling, but the beauty and mystique of this gemstone make it a treasured possession for generations to come.