October boasts not one, but two recognized birthstones: opal and tourmaline. However, opal holds the distinction as the traditional October birthstone, steeped in history, lore, and renowned for its captivating play-of-color. This article delves into the fascinating world of opal, exploring its origins, gemological properties, historical significance, and the symbolism that has made it the “Queen of Gems” for centuries.
History and Lore
The story of opal begins in India, where the earliest opals traded westward were known as upala, a Sanskrit term meaning “precious stone.” This name evolved into opalus in ancient Rome, where the gem was highly prized, considered a symbol of hope and purity, and valued as much as diamonds. Ancient Greeks believed opals bestowed the gift of prophecy and offered protection from disease. Throughout Europe, opal was long regarded as a symbol of truth and purity, embodying the virtues of all colored stones.
However, the perception of opal has shifted over time. While once universally admired, a 19th-century novel falsely linked opal to bad luck, briefly diminishing its popularity. This association was largely unfounded, and today, opal is once again celebrated for its beauty and positive attributes. It is also the traditional stone gifted for the 14th wedding anniversary.
Geological Formation and Sources
Opal is unique in its composition: a hydrated amorphous form of silica. This means it lacks a crystalline structure, setting it apart from many other gemstones. The “play-of-color,” opal’s most defining characteristic, is a result of the diffraction of light by microscopic spheres of silica within the stone.
The vast majority of the world’s opal supply originates from Australia, accounting for over 95% of production. Within Australia, specific regions are known for particular types of opal. Lightning Ridge is famous for its black opal, characterized by a dark background that intensifies the play-of-color. White opal is found in Coober Pedy and White Cliffs, while boulder opal, distinguished by its reddish hue due to the presence of ironstone, is sourced from Queensland.
However, Australia is not the sole source of this captivating gem. Mexico, particularly the state of Querétaro, yields fire opal, often translucent with a base color ranging from yellow to red. These can be either “precious” (displaying iridescence) or “common” (lacking iridescence, and sometimes referred to as jelly opals). Other sources include Ethiopia and Brazil, though these are less prominent than Australia and Mexico.
Gemological Properties
Opal’s properties differ significantly from those of more conventional gemstones. Its amorphous structure contributes to its relatively lower hardness, ranging from 5.5 to 6.5 on the Mohs scale. This means opal is more susceptible to scratches and abrasions than harder stones like sapphires or rubies.
Here’s a summary of key gemological properties:
| Property | Details |
|---|---|
| Chemical Formula | Hydrated Silica (SiO₂·nH₂O) |
| Hardness (Mohs) | 5.5 - 6.5 |
| Specific Gravity | 1.98 - 2.15 |
| Refractive Index | 1.45 |
| Color | White, black, orange, with rainbow flashes |
| Crystal System | Amorphous |
The defining characteristic of opal is its “play-of-color,” the iridescent flashes of red, orange, yellow, green, blue, and violet. This phenomenon is caused by the diffraction of light as it passes through microscopic silica spheres. The size and arrangement of these spheres determine the colors displayed. Different varieties of opal exhibit different patterns and intensities of play-of-color. Black opal, with its dark body tone, provides the most striking contrast and is generally the most valuable.
Varieties of Opal
Several distinct varieties of opal are recognized, each with unique characteristics:
- Black Opal: Characterized by a dark body tone (black, dark blue, or grey) that enhances the play-of-color. Primarily sourced from Lightning Ridge, Australia.
- White Opal: Exhibits a light or milky body tone. Found in Coober Pedy and White Cliffs, Australia.
- Fire Opal: Typically translucent with a yellow to red base color. Sourced from Mexico. Precious fire opal displays iridescence, while common fire opal does not.
- Boulder Opal: Contains ironstone within the stone, giving it a reddish hue. Found exclusively in Queensland, Australia.
Symbolism and Metaphysical Beliefs
Throughout history, opal has been imbued with various symbolic meanings. As previously mentioned, it was once considered a symbol of hope, purity, and truth. Bedouins believed opal held lightning and fell from the sky during thunderstorms.
While some maintain that opal is unlucky, this belief is largely a result of historical fiction and is not supported by gemological evidence. Today, opal is often associated with creativity, luck, and emotional balance. It is believed to stimulate imagination, enhance self-expression, and promote emotional healing.
Care and Cleaning
Due to its relatively low hardness, opal requires careful handling and cleaning. It is susceptible to scratches and can be damaged by harsh chemicals or extreme temperatures.
Here are some guidelines for opal care:
- Avoid exposure to harsh chemicals, such as household cleaners, cosmetics, and hairspray.
- Clean opal jewelry with a soft cloth and lukewarm soapy water.
- Avoid ultrasonic cleaners and steam cleaners, as these can damage the stone.
- Store opal jewelry separately from harder gemstones to prevent scratches.
- Opal can dehydrate and crack if exposed to prolonged heat or dryness. It’s advisable to occasionally immerse the stone in water to replenish its moisture content.
Conclusion
Opal, the traditional October birthstone, is a gemstone of remarkable beauty and captivating lore. From its ancient origins in India to its modern-day appreciation as the “Queen of Gems,” opal has enchanted jewelry lovers and spiritual seekers for centuries. Its unique play-of-color, diverse varieties, and symbolic associations make it a truly special and cherished gemstone. While requiring careful handling due to its relative softness, the allure of opal continues to endure, solidifying its place as a treasured birthstone and a testament to the wonders of the natural world.