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All About Our Exclusive Australian Boulder Opals

The freeform boulder opal cabochons that we supply here at Kernowcraft are a great example of how we pride ourselves of providing high quality stones from suppliers we trust. On this page we share the amazing story of our boulder opal suppliers as well as lots of interesting and useful information about the stones themselves.


Boulder opal is a beautiful stone that comes from the opal fields in Western Queensland. Here the opal fields cover a huge inland area of Queensland.

The term ‘boulder opal’ covers three sub categories of opal which are all formed in sandstone and ironstone...

The most common is Boulder Matrix, which comes from the fields of Yowah and Koroit in the South West of the state where beautiful ‘pictures’ are created between the matrix (the host rock) and the opal that entwines around it creating little works of art.

Then there is what is termed as Boulder Opal, which comes from a seam of coloured opal in the rock which is cut and polished to reveal opal with colours that flash and move together in one band of colour or colours.

The rarest of all three is Opalised Wood (this is the cutters favourite type of boulder opal). This forms in roots of wood where the matter decomposes leaving gaps where the opal, a combination of silica and water, trickles into it. Over a process which takes millions of years, unique patterns are formed between the opal and the fossilised wood.

Below is a video showing an example of how a boulder opal is found in ti's host rock before it is cut for making jewellery or other services. 


Once mined, the rough opal is hand cut into freeform cabochons ready to be set into precious pieces of jewellery. The cutter takes pride forming the cabochons into shapes that follow the natural flow of the stone, keeping in mind how the piece will look once set in a piece of jewellery. Each piece is unique; no two stones are the same unless they are cut from one larger piece of opal or from one piece which has a natural split down the middle. It is because of this that they will cut pairs or sets with matching pieces whenever possible.


With a relationship built by our managing director’s mother dating back over 18 years, we have the privilege of hand selecting each and every opal we get from our boulder opal supplier! We pick them with our customers at the forefront of our mind. They are a truly ethically sourced gemstone that our suppliers - a husband and wife team from Australia- have mine, cut and polish themselves. 


Our supplier is a husband and wife team who live in Australia and have spent the past 22 years in the opal industry - travelling through and living in the opal fields, gathering material to cut into beautiful cabochons to take to Europe, the UK and USA to show to jewellery designers and opal collectors. The opal fields they work on include Coober Pedy in South Australia which produces the white based opal, Lightening Ridge in Western New South Wales which produces the black opal and grey opal and Queensland – the home of the Boulder Opal which is the opal they love the most.


A visit from our opal supplier always causes quite a stir in the Kernowcraft office! As opals are best viewed in good, natural daylight, we’ll take a seat in by a window and delight in trays full of exquisite opals! As we cherry picked each and every boulder opal, we ensure the quality of the stones is of the highest standards in terms of marks, cracks etc. 

Our supplier brings a range to suit any budget and whilst we always ensure we pick opals we know are within the budgets of our customers, we do get the privilege of seeing boulder opals worth over £10,000 wholesale! The image below is an example of some of the very expensive opals found and cut by our suppliers - they range from £1000 to £500! 

Example of high value boulder opals


There is no standardised or set method for valuing opals as each one is so unique. However, there are a number of elements that make a boulder opal higher quality than others. 

The pricing of an opal is judged on the brightness of colour and pattern; the brighter and clearer the colours, the more expensive an opal can become (the rarest and most expensive of all opals are the reds). 

The following specifications are used to price a boulder opal: 

The Play of Colour: A brilliant range of the full spectrum of colours adds to quality. Red fire is generally the most valuable - more rare than any other colour. Green is more valuable than blue.

Brilliance: The brightness and clarity of the colours displayed. this can range from brilliant, bright to subdued or dull.

Pattern: The pattern in which the colours are displayed in and its distinctiveness.


When picking opals we try to ensure we select something for everyone. We are constantly shocked by the variations between opals and how different they can be. Below is an example of some of the amazing boulder opals we have supplied in the past.

To browse our current collection of beautiful boulder opals click here. We get new stocks of boulders opals fairly regularly so if you can't find something suitable you can always contact us we may be able to source it for you.

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If you have any further questions, feel free to call our friendly team who will be more than happy to give you some advice through Facebook, Twitter, Email or simply calling us on 01872 573888 8.30am-4:30pm.

Alternatively, for more information and how to's on all areas of jewellery making visit our other Gemstone Setting Advice pages.