Opal, often lauded as the “Queen of Gems,” holds a captivating place in the world of gemstones. Celebrated as one of the birthstones for October, alongside tourmaline, this mineraloid is prized for its remarkable play-of-color – a dazzling display of iridescent hues that shift and change with the viewing angle. Traditionally associated with loyalty, faithfulness, purity, hope, and confidence, opal is believed to enhance both visual acuity and the power of imagination. While historically a rare and highly valued gem, particularly within European aristocracy, significant discoveries in the 19th century, and more recently, have broadened its availability and cemented its status as a cherished gemstone.
A History Shrouded in Etymology
The origins of the name “opal” remain a subject of debate. Most scholars trace it back to the Latin word opalus, first recorded around 250 BC. However, the ultimate source of this term is uncertain. Some propose a connection to the Ancient Greek opallios, meaning “to see a change in color,” aptly describing the gem’s defining characteristic. Others suggest the Sanskrit upala, meaning “precious stone,” as a more likely root.
For centuries, opal was considered a symbol of good fortune, and some even believed it could bestow invisibility upon its wearer. Before the substantial finds in Australia, European access to opal was limited to a single location in present-day Slovenia, contributing to its mystique and high value. The gem’s historical significance extends beyond adornment; it was burned as incense and valued for its perceived magical properties.
Geological Formation and Modern Sources
Opal is not a true mineral but a mineraloid – an amorphous solid with a chemical composition similar to hydrated amorphous silica. It forms through the gradual natural heating of silica gel found within cracks in rocks. The resulting structure allows for the diffraction of light, creating the mesmerizing play-of-color that distinguishes precious opal from its common counterpart.
Historically, yellow amber and opal were often confused, both reaching the Middle East and Western Europe through trade routes. Yellow amber, derived from evergreen trees, shares a similar color profile and was also valued for its ornamental and incense-burning qualities.
While Australia remains a significant source, Ethiopia has emerged as a major player in the opal market. Discoveries in 2008 near Wegel Tena, and subsequently in 2013 to the north, have positioned Ethiopia as a rival to Australia in both quality and production. These Ethiopian opals, often referred to as Welo, Wollo, or Wolo opals, are found in the Tsehay Mewcha region, a volcanic plateau at the headwaters of the Blue Nile. The gems may also be associated with geographical names like Delanta and Wegel Tena. Prior to these discoveries, the Baltic Sea coast, particularly the area around Königsberg (now Kaliningrad), was the world’s leading source of amber and, historically, a key location for opal as well.
Gemological Properties and Varieties
Opal is categorized into two main varieties: precious and common. The defining characteristic separating them is the presence, or absence, of the play-of-color effect. This phenomenon occurs when light enters the opal and is diffracted by microscopic silica spheres within its structure, resulting in a spectrum of vibrant colors.
Precious opal exhibits this play-of-color, while common opal does not. Common opal can be translucent, yellow, orange, or brown, and often contains numerous minute bubbles, resulting in a cloudy or opaque appearance known as “bony amber.”
Ethiopian opals, particularly those from the Welo region, are known for their vibrant colors and are often found with a harlequin pattern. A particularly rare variety, blue opal, found in the Dominican Republic, displays a striking blue fluorescence under ultraviolet light. Dominican amber is also known for its transparency, contrasting with the more common cloudy and opaque varieties.
Symbolism and Metaphysical Beliefs
Throughout history, opal has been imbued with various symbolic meanings. Traditionally, it represents loyalty, faithfulness, purity, hope, and confidence. Beyond these virtues, opal is believed to possess properties relating to vision, both in terms of physical eyesight and the realm of imagination and dreams.
The gem’s association with good fortune dates back centuries, with some believing it could even grant invisibility. This belief likely stemmed from its captivating play-of-color, which seemed to create an illusion of shifting forms. The stone’s varied colors were also thought to embody the virtues associated with monochromatic gems of corresponding hues.
Care and Cleaning
Opal requires careful handling due to its relatively delicate nature. While not exceptionally rare today, its composition makes it susceptible to damage. As a hydrated amorphous silica, opal contains a significant amount of water. Exposure to prolonged heat or dehydration can cause it to crack or craze – develop a network of fine fractures.
Cleaning opal jewelry should be done with mild soap and lukewarm water. Avoid harsh chemicals, ultrasonic cleaners, and steam cleaners, as these can damage the stone. It is also advisable to avoid sudden temperature changes and store opal jewelry separately from other gemstones to prevent scratching.
Imitations and Treatments
Due to its desirability, opal has been subject to various imitations throughout history. These include young resins from trees, such as Kauri resin from New Zealand and copals from various regions. Other natural resins, like burmite from Burma and rumanite from Romania, have also been used as substitutes.
In more recent times, plastics like celluloid, cellulose nitrate, and various phenolic resins have been employed to mimic the appearance of opal. Some of these imitations are even marketed under misleading names, such as “African amber.”
Amber: A Related Resin
While this article focuses on opal, it is important to note the historical connection and occasional confusion with amber. Amber, a fossilized tree resin, shares some visual similarities with opal, particularly yellow amber. Like opal, amber was historically valued for its ornamental qualities and was also burned as incense. The term “amber” itself is believed to have originated from the Arabic word kahraba, which later became the Arabic word for electricity, referencing amber’s electrical properties when rubbed.
Conclusion
Opal, the “Queen of Gems,” continues to captivate with its ethereal beauty and rich history. From its uncertain etymological origins to its modern-day sources in Australia and Ethiopia, this mineraloid has held a prominent place in human culture for centuries. Its unique play-of-color, coupled with its symbolic associations of hope, faithfulness, and imagination, ensures that opal will remain a treasured gemstone for generations to come. The recent discoveries in Ethiopia have further solidified its position in the global gem market, making this mesmerizing stone more accessible to enthusiasts and collectors worldwide.