The October birthstone, opal, is a gem celebrated for its captivating play-of-color and rich history. Alongside tourmaline, opal offers a diverse range of hues and a legacy steeped in lore, from ancient beliefs about prophetic powers to modern associations with confidence and hope. This article delves into the origins, properties, historical significance, and care of this mesmerizing gemstone, drawing exclusively from available sources.
History and Lore
The story of opal’s name is somewhat shrouded in mystery. While most agree the term originates from the Latin opalus, first recorded around 250 BC, the precise etymology 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.
Throughout history, opal has inspired a wealth of stories and beliefs. Ancient Greeks believed opals bestowed the gift of prophecy and protection from disease. Europeans long considered it a symbol of purity, hope, and truth, with some believing it embodied the virtues of all colored stones. Bedouins held the belief that opal contained lightning and fell from the sky during thunderstorms. In ancient Rome, the gem was known as opalus and was prized for its vibrant display of colors.
Geological Formation and Sources
Opal is unique in that it is not a crystalline gemstone but rather a mineraloid – a material with a similar chemical composition to minerals but lacking a defined crystalline structure. It forms through the gradual natural heating of silica gel found in cracks within rocks. This silica gel, rich in water, solidifies over time, creating the characteristic play-of-color.
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 mines in Australia dramatically altered the opal landscape. Australia now dominates the opal market, producing a wide variety of colors and qualities.
Other sources include Myanmar (formerly Burma), where fine-quality peridot crystals can sometimes be found in crevices, and Tanzania, which has become known for producing pinkish and orangy red spinel, as well as purple and blue hues of opal.
Gemological Properties
Opal is categorized into two main varieties: precious and common, based on its ability to exhibit the play-of-color effect when exposed to white light. This phenomenon, a shifting display of rainbow hues, is what makes precious opal so highly valued. The dramatic play-of-color has been likened to fireworks, galaxies, and volcanoes by writers throughout history.
While not as rare as it once was, the varied colors and their interaction within opal continue to make it a prized gem. Opal’s hardness ranges from 5.5 to 6.5 on the Mohs scale, making it softer than many other gemstones and therefore less suitable for daily wear in rings. It is also vulnerable to thermal shock and can be damaged by some acids and even long-term exposure to acidic perspiration.
Symbolism and Metaphysical Beliefs
Opal is often associated with confidence and hope, making it a meaningful gift for those born in October. It is also the traditional stone given to celebrate the 14th wedding anniversary. Ancient beliefs attributed various powers to opal, including the ability to bestow prophetic visions and offer protection from illness. For centuries, the bands of color within sardonyx, another October birthstone, have made it a popular material for carving cameos and intaglios.
Care and Cleaning
Due to its relatively lower hardness, opal requires careful handling and cleaning. Steam or ultrasonic cleaners should never be used, as they can cause thermal shock and damage the stone. The safest method is to use a soft-bristle brush with mild dish soap in warm water. Opal should be stored with care to avoid scratching by harder gemstones. Exposure to high heat can also cause some colors to fade.
Other October Birthstones: A Brief Overview
While opal is the traditional October birthstone, tourmaline also shares this honor. Tourmaline boasts an equally impressive range of colors, offering a diverse selection for those seeking an alternative to opal.
August Birthstones: Peridot, Spinel, and Sardonyx
The August birthstones – peridot, spinel, and sardonyx – each possess unique histories and characteristics. Peridot, a yellowish-green to greenish-yellow gem variety of olivine, has often been mistaken for emerald and topaz. It is found in hardened lava, meteorites, and locations like Arizona and Myanmar. Spinel, named from the Latin word spina (thorn) referencing its crystal shape, comes in a wealth of colors and was historically mistaken for ruby. Major sources include Tajikistan, Myanmar, Sri Lanka, Vietnam, Tanzania, and Pakistan. Sardonyx, the most ancient of the August birthstones, is a combination of sard and onyx, popular in ancient Rome for seals and signet rings.
Gemstone Hardness Comparison
The following table provides a comparison of the hardness of the discussed gemstones on the Mohs scale:
| Gemstone | Mohs Hardness |
|---|---|
| Opal | 5.5 - 6.5 |
| Peridot | 6.5 - 7 |
| Spinel | 8 |
| Sardonyx | 6.5 - 7 |
Conclusion
Opal, the fiery October birthstone, continues to captivate with its mesmerizing play-of-color and rich historical significance. From ancient beliefs in its prophetic powers to modern associations with hope and confidence, this unique mineraloid holds a special place in the world of gemstones. Its delicate nature requires careful handling, but the beauty and mystique of opal make it a treasured gem for generations to come. The other birthstones discussed – peridot, spinel, and sardonyx – each offer their own unique appeal and historical context, enriching the world of colored gemstones.