How is this precious stone formed?

In certain desert areas of Australia, strange piles of white rocks dot the landscape. These are the residues of the thousands of aeration wells of craft mines patiently dug by researchers of opals. It must be said that in this region of the world, this precious stone takes on dark colors particularly appreciated by collectors.

Elsewhere, the range of colors is quite varied. But in its purest state, the opal is colorless. It is also a fairly young geological stone, formed over the millennia, especially near volcanic hot sources of hot water.

In waters rich in silica, many micro-organisms, such as diatoms, radiolar and even tiny sponges, can live and develop their skeleton made up of this mineral component. After their death, these structures are deposited and continue to accommodate silica crystals present in the water.

When the ideal conditions are met, after a few hundred millennia, the opal will form, as the water will get out of the mineral concretion that has been formed. The operation can also be carried out in rocky cavities as well as in bones, shells or even fossilized wood.

And if the microscopic spheres of silica manage to deposit regularly, they then form a unique arrangement in three dimensions which, under the effect of diffracted light, will make the stone shine with a thousand lights.