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October’s birthstone: Opal

Updated: Sep 15, 2021

All you lucky October babies have not one but two stunning birthstones to choose from: opal and tourmaline.


October’s birthstones are chemically very different, but they do have something special in common –both are stones of the rainbow in the mythology, folktales and lore of many cultures. It’s not hard to see why, as opal and tourmaline are found in myriad colour variations. In the first of October’s blog posts, let’s take a closer look at opal.

Octobers birthstone opal | www.gemstonedetective.com

How on earth can I begin to describe the beauty of an opal? Roman natural historian Pliny the Elder had the same problem two thousand years ago, writing that ‘of all precious stones, it is opal that presents the greatest difficulties of description, it displaying at once the piercing fire of ruby, the purple brilliancy of amethyst, and the sea-green of emerald, the whole blended together and gleaming with a brightness that is quite incredible.’


It’s difficult to argue with that! Every opal is different, and even the individual patterns and colours within each stone change according to the light and viewing angle. Finding the right opal is so personal that it is often said that the opal chooses you, rather than the other way round.

October's birthstone opal | gemstonedetective.com

Stunning Opal

There has been a lot of research about the formation of opal. There is no definite or conclusive evidence as to how opal is formed. They are all theories and there’s a lot of conjecture. Nobody can prove exactly why or how opal has formed.


The vast majority of the world’s precious opal is mined in Australia and, of all the country’s opal mining localities, Lightning Ridge is probably the most famous. It’s here that the coveted ‘black opal’ is mined—a stone with a dark base colour that beautifully emphasises the multi-coloured flashes and patterns within.

Boulder Matrix Opal | www.gemstonedetective.com

It’s the brilliance and vibrancy of these flashes of colour that determine an opal’s value. Red is the most desirable colour, but brighter flashes of blue and green are more valuable than a dull red. Generally, an opal displaying many different colours will fetch more than an opal with only one or two.


It’s no surprise that the mystical appearance of October’s birthstone has is associated with some incredible legends. One such story from the Aboriginal tribes of southern Australia tells how the dreamtime creator transported himself to earth in a rainbow. The place where he first touched the earth became a great plain of glittering stones in all the colours of the rainbow that had once rested there.


October’s birthstone has for thousands of years been associated with good fortune, prophecy and protection from harm, but it is also once believed to have been a stone used by witches—an association that means some people view opal as a symbol of bad luck.


Me? I think that anyone who owns such a beautiful stone must be blessed with the best of luck!


If you want to find out more about identifying, choosing and buying an opal, take a look at the Gemstone Detective Series, Buying Gemstones and Jewellery in Australia. You don’t have to be planning a trip down under to learn all you need to know about finding your perfect opal!


Next week, we’ll take a look at tourmaline.




Kim Rix GG (GIA)

Be sure. Be smart. Buy with confidence

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