Gemmology Matters: Opal is defined as SiO2·nH2O – an amorphous mineraloid comprised of hydrated silicon dioxide. The body colour of opal ranges from colourless, white, light grey through to dark grey and black. Precious opals from Australia usually contain around 6-10% water and consists of small silica spheres arranged in a regular pattern. However the truly unique thing about opal is that it displays all the colours of the spectrum in a "play of colour" caused by the diffraction of light passing through these silica spheres in the microstructure of opal. Opal has a hardness of 5.5 to 6.5 on Moh's scale meaning that it should be treated with care – they are often put in protective settings like bezels for this reason. Water content of opal varies greatly and in some cases where opals are stored in an extremely dry (dehumidified) atmosphere, damage (surface crazing) can result to the stone as moisture is lost from the stone structure.
Australia is the predominant source of precious opal supplying around 95% of the world supply. In contrast to the sapphire industry which is dominated by few larger operators, opal mining is done by many very small miners. Important opal mining areas of Australia include Lightning Ridge, Coober Pedy, Andamooka. Most of these areas also have active tourist industries and it is common to be able to buy opal direct from the source with many miners running small vertically integrated operations on site.
Mythology and Lore: Dreamtime stories tell that the creator came down to Earth on a rainbow, in order to bring the message of peace to all people. Where his foot touched the ground, the stones became alive and started sparkling in all the colours of the rainbow.
The fantastic colour play of opal reflects our changing emotions and moods. Opal is said to be able to solve depressions and to help its wearer find the true and real love. Opal is the anniversary gift for the 13th year of marriage.
Some people believe that opals are bad luck – in fact, there is no basis to this belief which seems to have stemmed from a misunderstanding of Sir Walter Scotts novel "Anne of Geierstein" – the Victorian readers having not read the final volume of the story jumped to the conclusion that the opal brought the tragic heroine bad luck – in fact Scott used it as a device to warn her of danger but this bad press caused a halving of opal prices and crippled the market for decades as this belief of bad luck took hold in the population. In fact, in Roman times, the gem was carried as a good luck charm of talisman, as it was believed that the gem, like the rainbow, brought its owner good fortune. In most cultures, it is regarded as having only positive properties. So there is no reason not to own one of these fascinating gemstones.
Alternatives in Multicolour: Fine gem opal is unique with nothing else like it. There is no real alternative to this gem. A gemstone with a shimmering iridescence of different colours is mystic topaz but this effect is created by coating the topaz with a thin layer of titanium – an interesting look but this does not compare to a natural opal where the "play of colour" is created by nature.
Images are from the Opals Down Under site which has an extensive catalogue of loose stones and jewellery as well as a very comprehensive information resource and forum for consumer help. An excellent Australian site.
Cheers for now from Aussie Sapphire
Dont forget to check out our new jewellery catalogue – sorry, no opal pieces but lots of great designs in our own sapphire and black spinel.