Opal is the birthstone for the month of October, along with pink tourmaline. It is also the stone given to celebrate the 14th year of marriage.
The name ‘opal’ is thought to be derived from the Sanskrit ‘Upala’, meaning ‘precious stone’ and later the Greek derivative ‘Opallios’ meaning ‘to see a change of color’. The Greeks believed they possessed the power of foresight, invisibility and prophecy, and the Romans considered Greeks as talismans for protection from danger.
Today, the most valuable opals come from Queensland and New South Wales in Australia, which have been the main producer of opals since their discovery in the 1870s. Opals are mostly found in Australia, Ethiopia, Mexico, the USA, South America, Canada, Brazil, Czech Republic and Slovakia.
The Australian opal was known as the ‘fire of the dessert’, formed from the weathering of sandstone deposited over older host rock in the Australian basin. The structure of of the gemstone is unique and comprised of tiny spheres of silicon dioxide, forming a pyramid shaped grid, interspersed with water. It’s the refraction of light through the spaces between these spheres that produces the recognisable opal characteristic, and unique ‘play of colour’. Australian opals are also valued for their stability, a key consideration for a gem containing 6-10% water.
Here in our Guildford shop we have a fine collection of opal jewellery, which you can see a selection of on in our dedicated category.
|Opal & Diamond Cluster Earrings||Opal & Diamond Cluster Pendant||Opal & Diamond Cluster Ring||Opal & Diamond Drop Pendant|
There are several classifications:
Solid means that the stone is a natural cut and polished, which does not have any kind of backing adhered to the stone to enhance the colour (as is the case with the partially fabricated stones – doublets or triplets). Queensland Boulder Opals – even though they have a natural brown ironstone backing which makes the stone darker – are still known as ‘solid opals’ since this is the natural formation of the stone.
Black refers to opal which has a dark grey to black body tone, and is generally mined in the Lightning Ridge area of New South Wales. As a general rule, Black Opal is the most valuable form, since its dark body tone causes the colours to be more vibrant.
Boulder is opal mined in Western Queensland. which normally has a natural brown ironstone backing attached to the stone. Boulder Opal usually has a very dark body tone and is the second most valuable form.
Crystal means any kind of opal which has a translucent or transparent quality. Translucent or transparent stones often have an enhanced clarity of colour, and for this reason it usually increases the value of a stone. The term ‘Crystal Opal’ normally denotes stones with a very light body tone, however Black Crystal Opal refers to a crystal opal, which has a dark body tone.
Semi-Black refers to opal which has a light to medium grey body tone and is therefore not quite dark enough to be called Black Opal. ‘Semi Black’ is generally found in Lightning Ridge, but is also found in White Cliffs and occasionally South Australia and can be one of the lesser valuable forms.
White means opal with a white to light body tone, and is also known as ‘milky opal’. White Opal is found in large quantities in South Australia, and the bulk of it does not have the same vibrancy of colour as found in other forms of the gemstone. For this reason, it is generally one of the least valuable forms.