Australia’s opal mines are responsible for approximately 90% of the world’s opals. Defined by its shifting colours, semi-transparency and silica composition, the opal – or particularly, the Australian opal, came into being between 30 and 40 million years ago, when heavy weathering began to dissolve the silica stored in the holes of a rock.



Opals have so many patterns that is nearly impossible to find two opals that look the exact same. Distinct and attractive patterns such as harlequin, rolling flash, Chinese writing, ribbon and mosaic are extremely rare and considered collectors’ items.



The value of an opal is determined by its type, its predominant colours, the clarity of these colours, and the patterns in which the colours are displayed. Other factors can include the shapes by which it is cut, its body tone, its brilliance or its transparency.

There is no governing body to value and price the world’s opals. Instead, demand from the international market decides what buyers must pay to obtain these gems. Demand relates to customer enthusiasm and may be directly influenced by the world economy or global fashion trends.



As opals are of such a rare and high quality, their scarcity is increasing on a global scale. In a good quality opal, the spheres of silica are packed together in a regular pattern – which creates a three-dimensional appearance with bands, or flashes, of colour.

Other factors at play within an opal’s quality include its body tone, brilliance, the thickness of its colour bar, and any faults such as cracked or natural inclusions.



When choosing and comparing opals, be sure to select a colour that appeals to you. In your comparison, be aware that an opal is judged on its range of colour and colour composition – so the more colourful an opal, the more valuable it will be.

It is also important to look at as many different opal types as you can to decide on which type you like best. If it’s a solid opal you’re after, for example, this research will help you ascertain that a solid opal is durable but also quite expensive in comparison to a composite opal.



It is extremely important to have a jewellery inspection conducted before you purchase an opal. A professional jewellers’ opinion may affect the gem’s value, and may also provide valuable insight on its care requirements for maintenance in future.

Once you’re ready for purchase, be sure to obtain a certificate of authenticity. Reasons for doing so include insurance purposes, re-sale value and accountability of the seller.


Where to purchase opals in Perth

If you’re on the hunt for a precious opal in Perth, look no further than the team at Allgem Jewellers.  Allgem jeweller Alfie has extensive training and experience with precious gems and Australian opals, and has qualifications as a Registered Valuer, Gemmologist and Master Jeweller. Conveniently located in Hay Street Mall in the CBD, our services involve the valuation of custom jewellery, gemstones and more. Contact our professional master jewellers to book in for your next jewellery valuation.