Gems generally get their colour because of certain metals contained in the mineral (for example purple amethyst is quartz containing tiny amounts of iron). However opals are unique because they display a rainbow-like display due to their intrinsic microstructure which diffracts white light into all the colours of the spectrum.
Australia took over as the major producer of opals in the world and remains the largest producer to this day.
In 1915 a group of people were prospecting for gold at the edge of the Great Victoria Desert northwest of Adelaide. Making camp one night, a 14 year old boy found an opal. This started an ‘opal rush’ and soon the settlement of the Stuart Range Opal Field was founded, better known now as Coober Pedy and together with Lightning Ridge in NSW, the bulk of the world’s opal continues to be produced.
Cleaning Your Opal
Solid opal should be cleaned gently with mild detergent in warm water and a soft toothbrush or cloth. Avoid bleach, chemicals and cleaners. Doublets & triplets may be wiped with a damp soft cloth and mild detergent, but should never be soaked or immersed.
Never allow anyone to clean your opal in an ultrasonic cleaner, as the intense vibrations may cause cracking in a solid opal, and water penetration in a doublet or triplet.
If your stone loses its shine or becomes scratched, bring it back to an opal cutter. After years of wear, small scratches and scuff marks cause an opal to lose its shiny polish and become dull looking. Professional polishing can bring new life to an opal which has become dull or scratched, and also check for claw damage and ensure the security of the setting.
If you need to store your opal away for a period of time, simply place it in a padded cloth bag for protection and store it away. For longer storage periods, place your opal in cotton wool with a few drops of water, then into a sealed plastic bag just to be safe. The water is not intended to soak into the stone but will prevent water coming out of the stone if it is exposed to very low humidity environments (for example, zero humidity storage safes).