Opal, alongside tourmaline, holds the distinction of being the birthstone for October. Celebrated for its captivating “play-of-color,” this gemstone has a rich history steeped in lore and symbolism, and continues to be a prized possession for jewelry enthusiasts. This article will delve into the origins, geological formation, gemological properties, historical significance, and care of this remarkable birthstone.
History and Lore
The story of opal’s name is somewhat shrouded in mystery. While most agree its origins lie in the Latin word opalus, first recorded around 250 BC, the source of that term remains debated. Some scholars believe it stems from the Ancient Greek opallios, meaning “to see a change in color,” aptly describing the gem’s defining characteristic. Others suggest the Sanskrit word upala, meaning “precious stone,” as a more likely root.
Ancient civilizations attributed various powers to opal. Ancient Greeks believed the stone bestowed the gift of prophecy and offered protection from disease. In contrast, Bedouins held the belief that opal contained lightning and fell to earth during thunderstorms. Europeans, for centuries, considered opal a symbol of purity, hope, and truth, even believing it embodied the virtues of all colored stones.
Geological Formation and Sources
Opal is unique in that it is not a crystalline mineral, but rather a mineraloid – a naturally occurring amorphous substance. It forms through a fascinating geological process. Millions of years ago, silica-rich water seeped into cracks and spaces within the earth. As this water gradually evaporated, it left behind deposits of silica gel. Over time, this gel hardened and solidified, creating opal.
The ability of opal to display “play-of-color” – the shifting, iridescent hues within the stone – depends on its structure. This phenomenon occurs when light diffracts through microscopic spheres of silica within the opal. The size and arrangement of these spheres determine the colors observed.
Historically, India was the primary source of opals brought to the Western world, where it was known as upala in Sanskrit. However, the discovery of rich opal mines in Australia dramatically increased the gem’s availability. Today, Australia remains the world’s leading producer of opal. Significant deposits are also found in Ethiopia, Brazil, and parts of the United States.
Gemological Properties
Opal’s defining characteristic is its play-of-color, which can manifest in a spectrum of hues, including clear, white, gray, red, orange, yellow, green, blue, magenta, rose, pink, slate, olive, brown, and black. The most rare and valuable opals display vibrant reds against a black background. White and green opals are more commonly found.
Opal’s hardness ranges from 5 to 6.5 on the Mohs scale of hardness, making it relatively softer than many other gemstones. This means it is susceptible to scratches and requires careful handling. It is composed of hydrated silica, with a chemical formula of SiO₂·nH₂O, where 'n' indicates a variable amount of water content.
Opal exists in two primary varieties: precious and common. Precious opal exhibits play-of-color, while common opal does not. Within precious opal, there are further classifications based on body tone and pattern. These include white opal, black opal, fire opal, and boulder opal. Opal doublets and triplets are also common, consisting of a thin slice of opal glued to a base material and covered with a clear quartz dome. These are created to enhance the play-of-color and provide stability.
Symbolism and Metaphysical Beliefs
Throughout history, opal has been associated with various symbolic meanings. It is often considered a stone of hope, confidence, and great achievement. Some believe it possesses powerful healing properties. Pink opal, for example, is thought to offer relief from ailments affecting the eyes, spleen, throat, pancreas, or bone marrow.
Beyond physical healing, opal is believed to promote a sense of peace and foster loving, devoted relationships within families. Modern metaphysical beliefs suggest opal can amplify emotions and encourage individuality. Tourmalines, also an October birthstone, are believed to balance hormones and fight against genetic disorders, and to calm nerves and elevate creativity.
Care and Cleaning
Due to its relatively low hardness and porous nature, opal requires special care. The safest method for cleaning opal is with warm, soapy water. Harsh chemicals or abrasive cleaners should be avoided, as they can damage the stone or any filler material present in doublets or triplets.
Prolonged exposure to water should also be minimized, as it can weaken the adhesive in opal doublets and triplets. Natural opal can fracture if exposed to high heat or sudden temperature changes. To prevent scratching, opal jewelry should be stored separately from harder gemstones like diamonds, rubies, sapphires, and emeralds. Opal may be treated by impregnation with oil, wax or plastic to enhance its appearance and stability, and these treatments can be affected by improper cleaning.
Conclusion
Opal, the captivating birthstone of October, is a gemstone steeped in history, lore, and geological wonder. From its debated origins to its mesmerizing play-of-color, opal continues to fascinate and inspire. Its association with hope, confidence, and healing adds to its enduring appeal. While requiring careful handling due to its relative softness, opal remains a cherished and beautiful gemstone for those born in the tenth month, and a prized possession for gemstone enthusiasts worldwide.