About Boulder Opals


At Clifton Opal, we cut, polish and sell only solid Natural Australian Boulder Opals.
This dark opal is found in Western Queensland and it forms naturally on its host rock of ironstone, which is cut to form part of the gemstone.

Boulder Opal occurs as thin veins in sedimentary ironstone boulders. The colour layer is naturally part of the dense brown ironstone base and is inseparable from it.

The inseparable nature of the colour layer and the ironstone base creates a beautiful free form finish with interesting shapes, giving boulder an individual look. This natural look combined with the intense and beautiful dark colours, has resulted in Boulder Opal enjoying an increased popularity in recent years.

Boulder Opal

Opal Formation

Opal is formed from layers of minute silica spheres that are uniformly layered. Between these spheres, silica gel is contained. Light is refracted passing through the gel, resulting in the beautiful rainbow colours of the opal. The resultant colours are in accordance to the size of the silica spheres and how closely packed they are. For example, the smaller spheres create the blue, which is more common and the larger spheres create the rarer orange and red opal. This rarity is reflected in the price.

The forming of the opal occurs when the silica gel in solution seeps through cracks and fissures in the rock formation. The silica settles and over millions of years forms a hard gel, creating the finished opal gemstone. It is estimated it can take up to 5 million years for just 1 millimetre of opal to form. Opalised dinosaur fossils have been found uniquely in Australia, sometimes inside organic material (for example wood, foliage or dinosaur bones) encasing the already historical and intriguing bones in the eternal beauty of the opal.


Opal Formation

Brief History

Opal has been cherished through out the centuries appearing in legends and history books. Opal goes back in history to 40AD. The first opals were discovered in the Hungarian mines and were a form of volcanic opal.

Famous figureheads like Cleopatra and Napoleon have been known to have a deep affection for this beautiful stone. The Emperor of France actually presented Empress Josephine with a stunning opal called “The Burning of Troy” as an expression of his love for her.
In the 18th century, jewellery house Tiffany promoted opal, giving this gemstone a kick-start in the European market.

Queen Victoria’s passion for and curiosity in Australia led to her insistence that members of the royal family be presented with an opal. This initiated the fashionable concept of owning an Australian opal in the British Empire.

Rene Lalique was also a famous jewellery designer in the early 20th century who used opals in many of his designs.