Opals for October

This month’s birthstone is the much admired opal and with many varieties and colour available. 



Originating from Australia, opal is formed from a solution of silicon dioxide and water. As water runs down through the earth, it picks up silica from sandstone, and carries this silica-rich solution into cracks and voids within the earth. As the water evaporates, it leaves behind a silica deposit. This cycle repeats over very long periods of time, and eventually opal is formed.

The pastel colours that we see in opals is down to the size of these silica spheres. Smaller spheres form more commonly which produces purple, blue and green colours whereas larger spheres are much rarer and these are the ones which give us the beautiful yellow, orange, pink and red colours. The price tag on an opal is solely determined by the colours that it displays with the latter examples being more valuable. 

The world’s most expensive opal is one that hails from none other than the infamous Coober Pedy in Australia. Known as the ‘Virgin Rainbow Opal’, it’s the most vibrant opal that the world has ever seen and is now owned by the South Australian Museum, priced at over $1 million.  This opal literally glows in the dark and it’s hard to believe that something so outstanding could have come out of the dirt. 

Another example of the opal is what we know as the ‘Fire Opal’. Mined in Mexico, these have been used for millennia and have even been discovered in Aztec burial sites. These unique opals are famed for their transparency and warm tones. Opposite to opals which display the solid opalescent play of colour, fire opals display a play of colour which is almost transparent. The warm yellow, orange and red tones are synonymous of their origin.


Like other opals, these are formed in the depths of ancient volcanoes where the same process of water running through the silica enriched lava repeats for thousands of years and eventually, fire opal is formed. 

These stones were held in high regard by the Aztec and Mayan civilisations and roughly translated, means ‘the stone of the bird of paradise’. 

The Jewellery Auction features various opal examples set in rings, pendants and earrings and even includes a unique pink opal. 



McTear’s sells more jewellery than any other traditional auction house in the dedicated jewellery auctions that take place twice monthly, run concurrently live online on a platform that attracts six million visitors annually from over 120 countries worldwide. For a complimentary, no-obligation valuation, contact a specialist on 0141 810 2880 or amy@mctears.co.uk.


Amy Cameron

Amy Cameron


Specialist, Jewellery, Watches & Coins 


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