What is Opal?
What is opal?
Opal is a beautiful precious gemstones endowed with multiple prestigious rainbow colors. Australia is the predominant country where Opals are found. Amazingly it is 1 of only six precious gemstone found on in the world, sharing a common family with diamonds, rubies, sapphires, emeralds and pearls. Silica (SiO2·nH2O) is what helps form Opal. The Silica is hydrated amorphous mineral. It has a water content ranging from 3 to 21% by weight, and is mostly between 6 and 10%.. It is classed as a mineraloid due to its amorphous character.. Crystalline forms of Silica are different. It is created in relatively low temperatures and often in fissures of many kinds of rocks. It can be found in sandstone, rhyolite,marl, limonite and basalt. Australia has opal as its national gemstone.
Where does opal come from in the ground?
90% of the worlds precious opals come from Australia. Other countries like Brazil, Indonesia, Ethiopia and USA are other locations for this. Types of opals mined in Australia are commonly referred to as
- White Opal
- Boulder Opal
- Black Opal
What creates the colors in Opal?
Opal hues cover a range of colors across the color spectrum. There may be a single color, two colors,3 or the whole rainbow spectrum.
The term “Play of color” is produced by a diffraction of white light through a structure of orderly arrayed silica spheres. The precious opal structure make light diffract through it.
Many colors can be seen depending on the form it takes.
Potch. What is this?
If you visit lightning ridge the opal capital of Australia, you will be given a bucket of Potch. Potch is the foundation for all opal. There is no color for the common opal.
However precious opal is different in that the Potch color will vary between grey to black or sometimes white. The Potch is not classed as a mineral but a mineraloid
How doe opal actually form?
A solution of silicon dioxide and water is what produces Opal. When water runs down through the earth fissures, silica is picked up from the sandstone. The water carries the rich silica solution into cracks and voids. These crack are either natural faults or decomposing fossils. When water evaporates it leaves behind its silica deposit. This is repeated over long periods of time allowing the opal to form.
Where are the opal fields in around the Australia?
There are a number of opal mining fields around Australia, however some are more well known than others. For example:
- Lightning Ridge in Queensland where our suppliers are from.
- Cooper Pedy in South Australia’
- White Cliffs
All these places are hot, dusty and hard places, so you will need to pack plenty of water and 4w driving for these.
The climnate can get above 50 degrees celcius so be warned…. better to buy from an online shop
Here is a map of Australia for some of those locations.