Opal flashes all colours of the visible spectrum. This will easily mesmerise any fortunate onlooker searching for the piece that will resonate with them.
The formation of Australian Opal is said to be due to a large inland sea which stretched from south west Queensland through northern New South Wales and down into South Australia thousands of years ago.
A common belief is that Australia was very close to Antarctica at this stage which made the water of the inland sea very cold. The water was also stagnant and took a long time to dry out as the continents started to shift. These conditions proved to be perfect for creating the world’s best Opal.
As the water started to dry out, it resulted in large scale and deep weathering of marine clay from the late cretaceous period. The weathering released silica which was sporadically deposited as Opal in suitable cracks, crevices, and cavities of fossils within the rock. This process of producing this beautiful Opal took many thousands or even millions of years to perfect.
The play of colour that is produced from Opal is from microscopic silica spheres which form in a regularly stacked formation of similar size. These silica spheres create voids which allow light to enter and refract out displaying the spectral colours that you can see.
Opal is very subjective, and as there are no 2 pieces the same, it is technically priceless, and every individual may like different stones to someone else. When pricing Opal, the main factors involved in per carat worth are:
Brightness and intensity of colour, the more different colours, whether colours are visible in all lights, from all angles, and pattern within the colours. Once an opal has been valued in terms of colour, it is weighed and the value is multiplied by how many carats it has. Larger stones may then be worth even more than the calculated figure because of the rarity of large stones with amazing colours.
Practically speaking, it makes little difference what is on the back of the stone or what the body tone of the stone is, even though there is a conception that Black opals are the most valuable. It is about what YOU like and are drawn too. The colour and brightness of the Opal are still the most important factor.