Natural opal is the term used for opal that has naturally formed in the ground in areas where silica is in high concentration through the natural fissures and cavities that have been formed underground. These cavities are filled with silica beads carried by the water or rain seeping down slowly over thousands of years.
Natural opal can have color or just be a grey or white color with no colorplay.
This is called common opal, and is found on every continent on Earth. Only very few areas where opal silica if found has gem color or color play. Lightning Ridge, Coober Pedy, Andamooka White Cliffs, Aramanga and Mintabie are just some of the areas where natural opal occurs in Australia. Ethiopia, Indonesia, Brazil and Mexico also produce natural opal with color and gem grade opal.
When a natural opal’s silica spheres are stacked evenly together the light has the ability to pass through the opal giving of colors of the rainbow. When the silica spheres are stacked unevenly the opal is common potch with no colorplay.
Natural opal can also form in volcanic ground and usually is weak and once taken out of the ground can crack or craze. One place in Australia that has volcanic opal is a place called Tintenbar on the far northern coast of New South Wales. Opal that comes out of the ground there can be very beautiful gems but they susceptible to crazing or cracking. Some pieces I have seen crumble in a few days of being out of the ground.
Doublets and triplets are not natural opal and have been manufactured. They have an appearance of looking like a solid natural opal but are not. They do have real opal in them but glue is placed between the opal and the black backing (common opal, onyx or plastic) to give the solid opal effect.
Gilson opal is another man-made type of opal that has the awesome gem consistency and is very hard to tell apart from real opal unless you have a trained eye. Synthetic opal is another type of opal that is not natural opal. It is made of a resin base.
If you are not sure of whether your opal is real, take it down to an opal expert and they will be able to decipher whether the opal is natural or not.
An opal is a well regarded gem and can be compared to diamonds. Prices vary from very little to prices comparable to diamonds per carat. It has a class of its own with the full spectrum of rainbow colors.
These gems are usually extracted predominantly from the mines of Australia, although there are a few quantities available in parts of the United States and South America. Some of the natural opals are used in its raw form but most of them are polished before they are used in the jewelry.
These are usually used by the person to decorate themselves and are used in line with the clothes they prefer to wear and their personality. There are numerous colors of opals to choose from. The attraction to opals have given many people the gambling fever or commonly known as the opal bug. Many people have wasted life savings to find the elusive red on black opal by exploration of the opal bearing ground.