There is perhaps no other gemstone that captures the imagination as much as the opal. It’s no surprise, however, given the vast array of colors that these unique mineraloids can display…from opaque and nearly colorless to possessing every color of the rainbow, opals have adorned our jewelry for thousands of years. In fact, it was in 1939 that the famous anthropologist, Louis Leakey, found ancient jewelry artifacts adorned with opals buried in a cave in Kenya that dated back to 4000 B.C.!
Opal is composed of hydrated silicon dioxide. The hydrated part refers to water, and opals can have from 3 to 30% water content. Due to its potential for high moisture, opal is sensitive to extreme temperature fluctuations, and can dry out and even crack in areas with low humidity and high heat. Opal is also quite soft, with a rating of 5.5 to 6.5 on the Mohs scale. In comparison, the emerald (fragile due to its naturally included and flawed formation) is rated a 7.5 to 8.0, while the diamond tops the list at 10. For this reason, care should be taken when wearing rings with opal stones (one hard knock and that beautiful opal could be ruined!). Though they’re best suited for earrings, pendants and necklaces, it’s hard to resist an opal ring or bracelet where you are able to admire its beauty along with everyone else.
Opal is found all over the world, but Australia alone is responsible for about 97% of all opal gemstones on the market. All one has to do is Google ‘opal images’ to see the incredible variety that’s out there. Even with all the variety, opals are generally divided into three subgroups: common opal, precious opal, fire opal.
Common opals usually display what has been termed opalescence, which is the milky-bluish hue that most people associate with opal gemstones. Precious opals diffract light, also known as ‘play of color’, and this is what gives an opal its unique rainbow color effect that changes when viewed at different angles. Though fire opals can diffract light as the precious opals do, they are more known for their overall vivid and intense color.
Though the cabochon (/ˈkæbəˌʃɒn/) cut seems to dominate the opal market, opals can be cut into a variety of faceted shapes, and also inlayed into everything from guitars to furniture. Some types of opal are rare, and thus very valuable. Below is a list of some of the more popular and well known opal varieties:
Black opal - a precious opal, highly sought after for jewelry design. Very rare and valuable.
Fire opal - Intense body color that is often translucent. Can be red, yellow, or orange. Sometimes called sun or Mexican opal.
Chocolate opal - This precious opal, brown in color, is the most rare and expensive opal in the world.
Common opal - An opaque and rarely translucent opal, these demonstrate no play of color.
Opal is the birthstone for October. In mythological lore, opals were thought to have absorptive powers, allowing the wearer to sense others’ thoughts or emotions. They were also thought to enhance creativity. Whatever their power, opals continue to captivate and inspire us through all their beauty and uniqueness.
Because opals are relatively soft, it is recommended to clean them gently with mild soap in warm water. You can use a soft toothbrush or a soft cotton cloth. When cleaning opal doublets or triples, do not immerse them in water (or swim with them!) as the glue that binds the layers together may weaken. When storing your opal jewelry, consider placing it in an airtight bag with a piece of damp cotton to prevent the stone from drying out.