October Birthstone Jewelry: The Opulent Opal
What is the October Birthstone? Composition and History
The opal is a unique gemstone because it’s not actually a mineral, but rather a mineraloid. This is because the composition of an opal is amorphous, formed of water and microscopic spheres of silica. In precious opals, these silica spheres are stacked on top of each other in thin layers which refract the light like a prism, giving the opal its fiery “play-of-color,” or iridescence. Common opals also exist, but their structure doesn’t allow any light to pass through the same way, so they don’t exhibit any iridescent “play-of-color”.
Opals have existed since the days of Ancient Greece and Rome. The Greeks believed opals would bestow the powers of prophecy and foresight, while the Romans believed opals were the most powerful of all the gemstones because they contained the colors of all other stones. Most opals today (about 95%) are mined in Australia, but other major opal deposits have been discovered in Ethiopia, Nevada, Mexico, and Idaho. In 2008, NASA even announced it had found opal deposits on Mars.
What Color is Opal?
As mentioned above, precious opals have a distinct play-of-color quality, allowing light to pass through the silicon spheres and display a rainbow of color – but there are also specific colors of opal. White opals are the most common, and these are considered to be the true October birthstone. Fire opals mostly lack the shimmering play of color, and are instead a translucent red, yellow, or orange. Black opals are the rarest form of opal with a mostly dark background, usually dark gray or blue-black, allowing a bolder play-of-color because of the contrast. These variations occur due to the conditions under which the opal was formed, but all you need to remember is this: the darker and more multicolored the opal, the rarer and more valuable it is.
Genuine vs. Lab-Created Opal
When the layered spherical structure of precious opal was discovered by scientists, it enabled them to create artificial opal in 1974. Since then, the creation of lab-created opals has been refined to the point where they are almost indistinguishable from genuine opals; the primary giveaway is that lab-created opals don’t contain any inclusions, whereas genuine opals do. As with other lab-created gemstones, lab-created opals are a more affordable option for those seeking to purchase opal jewelry, while still retaining the look and feel of genuine opals.
