How is an Opal formed

ImageMost of the gemstones that are found are treated artificially either by heating them at a certain temperature or by adding some kind of chemicals in them. But Opal gemstone is the only which does not undergo any type of artificial treatment.

After reading this article, you will have a very clear idea about the exact process on how an opal is formed

Opal, the natural gemstone forms in a very interesting way. It is formed from a combination of silicon dioxide and water. The stone is truly natural and is formed in a very beautiful manner. When water runs down through the earth, it collects all the silica present in the sandstone. This solution is formed by natural decomposition. When the water finally evaporates under extreme conditions of heat, then it forms small oval structures which take the shape of an opal when they are hardened.

The silica rich solution which is formed in the volcanic rocks creates cracks and voids by the weathering process. Many fossils releases molds that acts as a secondary mineral in the formation of this gemstone. Miners call it by the name of potch and the mineralogist terms it as Common Opal. During the initial formation, the gemstone is in its unnatural state and therefore many pores are formed in it. Opaline Silica fills all those pores, thereby accumulating all the grains.

Variation inside an opal depends upon a number of factors. Climate plays an important role in the formation in the variation. Wet climate helps to maintain the amount of silica inside the stone where as a dry climate significantly reduces the water content inside the stone thereby making it harder. Moreover, regions where volcanic eruptions take place also a material known as the white kaolin is formed and thereby it helps to produce an Australian Opal.

Many scientists as well as mineralogist are still researching in order to find out the exact way by which an opal is formed. They are constantly trying to figure out the chemical conditions or the acidic reactions that are responsible for the creation of an opal.  Opals mainly have their origin from the Great Australian Basin. Three other places that are Lightning Ridge in New South Wales, South Australia and Queensland boulder where black white and matrix opals are found respectively.

Another important member in the family of Opal is the Boulder Opal. Even this gemstone is formed naturally. But the appearance of such kind of opals is quite different. These stones are generally elongated in shape. They are mainly formed by the accumulation of sandstones. Though, some minute cracks might develop in this opal but it does not affect the appearance of the stone in any way. Boulder opals are cut into fine precision by the gem cutters to give them the desired shape.

Matrix and Pipe are the two important opals that are yet other members of the opal family. Matrix Opal is very rare in existence and they are mainly formed by iron stone. Pipe Opal on the other hand is like a pipe structure that is usually longer in shape. Hence, Opal Beads are one of the most natural gemstones that are found on earth.

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Source : http://www.streetarticles.com/jewelry-diamonds/how-is-an-opal-formed

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