What is an opal?
There are two types of opal: precious and common, but in jewellery we really only see the precious rainbow-coloured gemstones. Opals are naturally occurring gems that can be found in the fissures of a variety of common rocks.
Made up of hydrated silica these entrancing stones are formed by silica deposits collected by water as it runs through the earth. The silica-rich water eventually travels into tight cracks and fissures in rocks where it gets trapped, as the host rock heats up the water evaporates but the silica remains and grows into opal. This process may sound simple enough but it takes between 5-30 million years to complete, so it’s not one you can get in an instant.
Where does the name opal derive from?
Opal comes from the Latin ‘Opalus’ which translates as “to perceive a colour change” and refers to the unique play of colour seen as opals turn in the light.
Why do opals have rainbows?
Opals are made of billions of microscopic spheres of silica all irregular in size and squashed together in a matrix to form a gemstone. As light enters the gemstone it is forced to squeeze into the tiny gaps between these spheres and then burst out the other side, splitting the white light into the spectral colours of the rainbow. The colours we see dancing across the surface of the stone depends on the size of the silica sphere and the gaps between it and the next sphere.
Where in the world do we find opals?
As with most gemstones there are many countries where opals can be found and mined, these include: Mexico, Brazil, Honduras and parts of the USA, however 95% of all opals are mined from Australia, with the first Australian opals were found in 1849 by geologist Johannes Menge.
History of opal discovery
Whilst Australian opals were discovered in 1849, there have been opal relics found in Kenya that are believed to date back as far as 4000BC and opals have been revered for centuries. A famous quote comes from Pliny in 75AD who wrote “For in the opal you shall see the burning fire of the carbuncle or ruby, the glorious purple of the amethyst, the green sea of the emerald and all glittering together, mixed after an incredible manner”
Opals, much like many gemstones, have long been shrouded in superstition. It used to be believed that their colourful surfaces could preserve the colour of blond hair and health when worn. However Opals also came with negative connotations with a popular book by Sir Walter Scott creating a superstition that it was unlucky for anyone not born in the month of October to wear the gemstone.
Due to the near monopoly Australia has on the opal market it is no surprise that many of the famed stone trace their provenance back to the continent. One of the most famed stones is the Fire Queen. Originally known as the Dunstan’s stone, it was found in 1901 by Charlie Dunstan this precious stone weighed an incredible 900ct, however black opals were not in demand at the time and the miner sold it for a pitiful £100. The stone resurfaced in 1928 with a valuation from the Chicago Museum of £40,000. The stone eventually was sold at auction for a sizeable £75,000 to J.D. Rockefeller and she remains in the family’s collection.
Caring for your opal
As opals come from Silica and water they are stones that love moisture and the main key when caring for your opal is to make sure that your glorious little silica spheres don’t de-hydrate as this can lead to fine cracks appearing across the surface of your stone, known as crazing. It is therefore recommended that you keep opals in a dark and cool environment when not worn, and if displaying opals in a hot display case adding a little damp cottonwool bud nearby to keep the humidity levels up.
Aside from being water babies, opals are also soft stones, graded as a 3 on Mohs hardness scale, this means we recommend taking care when wearing them and keeping them away from harsh chemicals. If you want to clean your opal stone then a small bowl of warm water with washing up liquid and a soft toothbrush is the perfect way. If properly taken care of opals will last thousands of years in pristine condition.