Under the Opal name – from Latin “opalus” which means “precious stone” – there are several different types of this silica mineraloid: common opal (which is usually opaque), the white precious opal, which is the most known one used in jewelry, the black (precious) opal, fire opal, blue opal and golden opal being few of them.
Precious opals are Australia’s national gemstone. South Australia accounts for 80% of the world’s supply of precious opal, with Australia accounting for 95-97%. Coober Pedy, Andamooka, White Cliffs and Lightning Ridge are well known mining places in Australia. Ethiopia is another important source of opal. There are also mines for precious opal in Brazil, the United States, Canada, Honduras, Indonesia, Zambia, Guatemala, Poland, Peru, and Guatemala.
Opals are formed by water and silicone dioxide. As a relatively low temperature deposit, it may form in thin, fissured areas of rocks, such as limonite, sandstone, rhyolite, salt, and basalt. In Australia, opal is mined from sandstones and mudstones. Groundwater was contaminated by silica from these weathered sedimentary rocks. The groundwater penetrated downwards through small faults and joints in the rocks. The silica in groundwater was trapped between the sandstone and underlying rocks, which hardened the water into a gel and created opals.
Unlike the other forms of silica, which are minerals, Opal is an amorphous hydrated form of silica mineraloid with a water content that can vary from 3 up to 21%. In opals, spheres of silica are arranged in a regular pattern with water between them. Diffracted white light is broken up into the colours of the spectrum by the silica spheres, generating what we call ‘opalescence’. Spheres of larger diameter provide all colours, while those of smaller diameter provide only blues and greens. The rare Fire Opals only occur where conditions allowed large silica spheres to form.
Purification. Good luck (in old traditions). Hope – in Asia. Water Element.
Several Opal legends, myths and traditions have been created and perpetuated from very old times. By most cultures, it was regarded as magical and the luckiest of all gems. In the Middle Ages, people believed the opal had the virtues of various gemstones whose colors are represented in the opal’s spectrum, and as such brought great luck to its wearer. An Arab belief was that Opals have been created by a lightning strike and their flashes of color are caused by trapped light. North European blond women of the medieval period wore necklaces encrusted with opals so their hair would never fade or darken. As an old myth goes in France, bay leaf-wrapped opals confer invisibility. There have also been myths less favorable to this beautiful stone: apparently the stone color faded when a member of nobility had it sprinkled with holy water, therefore this contributed to the belief that the stone is “bad luck”. There was also a novel written in 1800 by Sir Walter Scott (“Anne of Geierstein”) that perpetuated the belief that the stone was unlucky for anyone not born in October. Queen Victoria however was very fond of Opals and gifted opals to all her daughters, ignoring the bad luck myths altogether. Many of the myths are still around today: some people still believe that opals lose their luster once their owner dies, giving or accepting a gift of an opal is a bad idea and engagement rings should not contain opals.