There is a legend in Arabia that the opal is made up of lightning.
Writers tend to compare the color of opal to volcanoes, galaxies, and fireworks. Admirers give extraordinary opal poetic names such as Pandora, Light of the World, and Queen. In ancient Rome, this gemstone symbolized love and hope. The Romans gave it the name "opalus", which is synonymous with precious gemstones. Many cultures believe that opal has a supernatural origin and power. The ancient Greeks believed that opals could give the gem's owners the gift of prophecy and protect them from the threat of disease. Europeans have long considered this gem to be a symbol of hope, purity and truth.
color
Opal exhibits the so-called play-of-color phenomenon, and when opal has a play-color, it is called a valuable opal. The main categories of precious opal are albumin, melanin, gravel protein, crystal protein, or aqua opal. Fire opal, also known as Mexican opal, sometimes does not appear to be a play-color.
Clarity
For opal, clarity refers to the degree of transparency and absence of inclusions. The clarity of opal can range from completely transparent to opaque. A cloudy or milky background color may sometimes represent a lack of stability. Opal may have cracks and surface features. The matrix or host rock, as well as signs of cracks and subtle crack networks, can affect the solidity and value of opal.
source
The best opals come from all over the world. The most important sources are Australia, Mexico and Ethiopia.
Processing methods
Opal can be infused with oil, wax or plastic. Opal bilayer or opal triplet stone is a thin piece of opal that is glued to a substrate and covered with a thin transparent dome of quartz. These gemstones are more scratchy but less valuable. Some opals may be dyed.
Maintenance and cleaning
Using warm soapy water is the only safe way to clean the opal. Opal is sensitive to high temperatures or excessive drying, which can lead to cracks or internal cracks.