Opals would have to be one of the most fascinating and mysterious gemstones of all. Their kaleidoscopic play of colour is enchanting and sets them apart from all other precious gems. Precious opals can potentially display all the colours of the rainbow with reds and oranges being the most rare.
Australian precious opal has the reputation of being the finest quality in the world. In 1993 the Governor General, Sir Bill Hayden, declared opal as Australia's national gemstone - our nation and opal are inextricably linked.
At BUNDA we have a deep experience working with this unique and precious gemstone that spans over two generations. This knowledge, coupled with the vision and the skill to create jewellery pieces which are like sculptures, enables BUNDA opal jewels to display the mesmerizing beauty and sheen of this magnificent gem to maximum effect.
Opals have been treasured by man since the civilizations of Ancient Greece and Rome. Our name for opal comes from both the Ancient Greek, Opallios, and the Latin word, Opalus, which both mean, 'To perceive a colour change'.
Pliny the Elder wrote the inaugural Natural History of the World, which was first published in 77AD. In this most important publication he wrote that opal is the most highly prized and valuable of all gemstones in the empire, “For in them you shall see the living fire of ruby, the glorious purple of the amethyst, the sea-green of the emerald, all glittering together in an incredible mixture of light”. He wrote that opals hailed from India however the opals that the Romans prized came from the Czernowitz mine in Hungary.
Opals were perhaps first discovered 10,000 years ago in the Virgin Valley in North America and subsequently in Ethiopia around 4000BC. The Ethiopian opals slipped out of history until they were rediscovered in 1990.
During the 1890's, opal deposits were discovered at Lightning Ridge, NSW, Australia and the first shafts were dug around 1901 or 1902. The brilliance and intense colours of these opals had never been seen before and it was rumoured by Hungarian opal miners that these new deposits were fakes.
Australia now produces 90-95% of the world's precious opal and some of the major mines are in Lightning Ridge, Coober Pedy, Andamooka, Winton and Yowah.
In Australia, precious opal is found in Cretaceous era sandstones and mudstones. These sedimentary rocks were deeply weathered and this weathering released silica into the groundwater. Small faults and joints in the rocks formed pathways for movement of the groundwater as it penetrated downwards. Impermeable barriers between the sandstone and the underlying rocks trapped the silica-carrying groundwater where it slowly hardened into a gel forming opal in veins and lenses. These unique conditions enabled top quality precious opal to form and Australia is the only part of the world where opalised animal and plant fossils have been found.
At Lightning Ridge in NSW, small opalised dinosaurs and primitive early mammalian remains, together with shallow marine shellfish and crustaceans have been found.
Opal is essentially a form of hydrated silica, which means it contains water in its structure. Water content varies in precious opal from 3-10% and from 1-21% in other types of opal.
In 1964, some clever researchers at the CSIRO in Melbourne revealed the micro structure of opal with the use of an electron microscope which was cutting edge technology at the time. They discovered that opal is made up of an orderly three dimensional lattice of minute silica spheres in optical contact.
It's the arrangement of these spheres that produce the fascinating play of colour which opal is famous for. The spheres are stacked in a three dimensional grid that diffracts white light and breaks it into all the colours of the spectrum. The larger spheres are responsible for oranges and reds while the smaller spheres produce blues and greens.
Opal is amorphous which means its physical, chemical and optical properties are the same in all directions and it lacks crystalline structure. Light cannot pass through solid opal however it's reflected and refracted through the layers of silica spheres and produces a sheen known as opalescence or in the case of precious opal, play of colour.
Opal is 5.5 to 6 on the Mohs scale of hardness making it suitable for regular wear however attention should be paid when wearing an opal ring. Avoid wearing opal while playing sports, gardening or any physically strenuous activity. Australian opal is not porous, however it's best to avoid harsh chemicals and detergents for cleaning and get your opal jewellery professionally cleaned.
The three main types of Precious Opal are:
Precious Black Opal - Precious black opal is solid opal which shows a play-of-colour on a black background or body tone when viewed face up. The best known source of black opal is Lightning Ridge in New South Wales.
Precious White Opal - Precious white opal is solid opal which displays play-of-colour on a pale background or body tone when viewed face up. The most famous source of white opal is Coober Pedy in South Australia.
Boulder Opal - Boulder opal hails from Queensland and is a combination of opal and rock, normally ironstone or sandstone. The precious opal with play-of-colour runs as either seams through the ironstone or there is an undulating contact between the opal and rock. It is considered to be a solid piece and not a composite stone.
Selecting an opal is like selecting a work of art. The magic of the stone rests with the play of colour - as your eye travels across the stone, vivid intense colours reveal themselves in an enticing display.
For fine jewellery pieces, precious opal is desired. Precious opal has three categories: black, white and boulder. Black opal is perhaps the most famous with its rainbow colours flashing dramatically against a black background. Black opals with all the colours of the spectrum including red and orange are the most rare and valuable.
White opal has the same play of colour on a pale background.
Finally, Queensland boulder opal has a matrix of ironstone with vivid seams of opal that look like sculptural works of art.
The important thing when selecting a precious opal is to know that you have a solid piece. There are many doublets and triplets on the market which can look fantastic however are a fraction of the value of solid precious opal. A doublet is a thin slice of precious opal that is then layered onto a piece of potch or common opal, kind of like a gem sandwich. The triplet will have a layer on top of the opal slice and potch, hence the name. When viewed in cross section the layers of these stones are even and flat.
Natural solid opal may have an undulating appearance and will not have any precise or even layers. There is nothing wrong with selecting an attractive doublet or triplet, however it must be disclosed to the client that this is what they are purchasing.
At BUNDA we have several trained gemmologists in the team who can explain in detail the nuances of precious opal and how to select the perfect gem for you.
The name for Opal derives from the Latin word, Opalus, and the Sanskrit word, Upala, which translates as Precious Stone. Opals have been revered by many cultures, including the Aztecs, Ethiopians and Aboriginal Australians.
One of the dreamtime stories regarding how opal came to be tells of a beautiful butterfly, Pallah-Pallah, who falls asleep on a snow capped mountain and as the snow melts, the colour from her wings seeps into the earth thus creating precious opal.
The Romans believed Opal brought hope and good luck. In France it was thought to render the wearer invisible!
During the 19th century, Sir Walter Scott's novel, Anne Of Geirstein, tarnished the reputation of opal in Europe and prices plummeted. In the novel, the supposed bewitched heroine's magic opal loses its colour due to contact with holy water and she dies as a result. In the third volume all is resolved and the opal is absolved of blame however many didn't read this tome and opal was thought to bring bad luck for subsequent decades.
Fortunately we now know better, and the reputation of opal being one of the most beautiful and fascinating gems has been restored. The metaphysical properties of precious white opal are bringing an intensification of emotion and purification, while precious black opal is said to help one manifest one's intent, amplify emotions while revealing and releasing psychic wounds.
