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Opal is a semi-precious stone with a beautiful look and a wide range of hues. According to the most widely accepted geological hypotheses, it is generated by silica-laden water that crept to the earth’s surface via sandy soil and filled fractures and empty spaces before evaporating. The residual material then solidifies after being treated to extremely high pressure and heat to make opal. However, it is thought that in the opal fields of Virginia Valley, Nevada, USA (where black opal is also created), water laden with heated silica rises to fill the empty spaces and form opals.

Some scholars believe that the origin of the opal stone found in the Virginia Valley in the United States of America dates back about fifty thousand years, while others believe that the opal stones found in the “Lightning Ridge” region of the United States were formed in the Cretaceous period a hundred million years ago, when about one centimetre (a little more than a third of an inch) of opal grew by rain about five million years ago. The majority of the fossils discovered in that location were produced during the Cretaceous epoch, according to this idea.

أحجار أوبال خام - كيف يتكون حجر الأوبال

Appearance of Rough Opals

Recently, some scholars have found The fossil voids were formed much later than that, while some had another opinion on this if they said that the formation of those fossils may have occurred in less than a hundred thousand years.

Composition of “Boulder Opal”

Boulder opal from Queensland is created in a somewhat different way than other forms of Australian opal due to iron impurities. This fossilisation or solidification happened as a result of the ionisation (conversion of sedimentary sediments into ions). The opal stone solution in the Idaho Spencer mines in the United States of America was a secondary sediment conveyed by hot spring activity.. The opals were placed in layers as a result of many eruptions in the rocks throughout time. Because the majority of these layers are thin, triple opals occur, which are the most beautiful in the world. Hot-water opals are deposited in consecutive layers within small geodes, making Spencer Mine opals a perfect choice for triplets since their thin layers are of exceedingly good quality and the valuable stones are highly clear with outstanding colour intensity.

Appearance of a number of opals

Chemical conditions

Scientists agree that acidic conditions must exist at some point during the formation of silica layers, which may have been created by microbes. It is also believed that aluminum oxide, ferric oxide or magnesium oxide, as well as sodium chloride or sodium sulfate, are needed for these acidic conditions. In South Wales, the initial study suggests that these microbes played a role during the deposition of Cretaceous sediments, abundant organic matter, and montmorillonite (smectite) clays in some of the sediments, providing an ideal habitat for microbes to feed and reproduce. It also causes acid and enzyme residues that are secreted by microbes in the chemical weathering of clay minerals and feldspar in the surrounding rocks. Finally, the continuous feeding and waste production processes of microbes create physical and chemical conditions favorable for the formation of opals.

Shaping Opals

Opals are formed in bottles using electricity (a chemical solution that has been electrically charged). ) which takes several weeks to see some color in it. This is only a gelatinous substance and not a solid, and it is believed that this process occurs in nature and would explain how the opal entered the porous volcanic tuff stone or how it entered the center of the nucleus.

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The appearance of the opal stone after its formation

Opal’s Acquisition of its Colors

Scientists discovered that opals were made from millions of microscopic silica balls organised in a regular pattern using an electron microscope. When white or the regular colour of the sun shines, it is split into colours by smaller gaps or even gaps between each of these balls through which the light is neutralised. Due to the tiny size of the balls in an opal, the colours generated are the deeper colours of the rainbow – violet, indigo, and blue. When the balls are big enough, The colours created are distinct from the preceding hues. The hues in this example are yellow, orange, and red. When the balls are stacked in a regular fashion, precious opals are discovered. It appears that the opal stone was generated in separate sections of the same field by different forces, resulting in a stone with a distinct personality.

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