{"id":6125,"date":"2024-02-12T13:46:40","date_gmt":"2024-02-12T11:46:40","guid":{"rendered":"https:\/\/efirgems.com\/opal\/"},"modified":"2025-03-06T11:26:22","modified_gmt":"2025-03-06T11:26:22","slug":"opal","status":"publish","type":"post","link":"https:\/\/efirgems.com\/en\/opal\/","title":{"rendered":"Opal"},"content":{"rendered":"\t\t
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Opals are one of the most interesting gemstones. Jewellery with natural opals is considered to be arrisocratic and captivates with its vision. Made up of silica and water molecules, these mineraloids do not form a crystal lattice but are amorphous in structure. With a hardness of 5.5-6 on the Mohs scale, a conchoidal fracture and a waxy lustre, opal is common in its plain form. Our interest focuses on precious opal, which is very rare and formed by complex geological processes.<\/p\n

It is distinguished by its specific patterns resulting from diffraction of light. The term opalescence describes the beautiful multicoloured reflections. \"The 'play of colours' is formed by microscopic spheres of silica arranged in a grid. When light passes through them, the optical phenomenon of diffraction is formed (\"Light deviates from linear propagation when passing through a small aperture or narrow slit (0.1-1 mm). In this case, the light rays propagate not only in a straight line but also sideways, so that coloured edges - diffraction rings or streaks - appear around the light circle or light streak.\") The size of the spheres and their geometric arrangement determines the color and quality of the refracted light.<\/p>\n

Each opal is unique and no two stones are the same in nature.<\/p>\n<\/div>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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How is the quality of opal determined?<\/h4>\n

It is one of the most complicated gemstones to evaluate due to the fact that it depends on many factors. Below are the main factors in evaluating it, as well as an easy way to distinguish Ethiopian from Australian opal.<\/p>\n

1.Origin<\/h5>\n

The most common opals originate from Australia and Ethiopia, and it is considered the national stone in Australia. It is also found in Mexico and the United States (Nevada) among others. Australian opals have a reputation for being the most valuable in the world. Each country has its own principles in valuing its opals.<\/p\n\n\n

Australian opal or Ethiopian opal?<\/h6>\n

The formation of Australian opal is due to acid weathering during the drying of the central Australian landscape. This occurred when the vast ocean covering 60 percent of Australia began to retreat. It began leaching minerals from the soil, resulting in pockets and cracks where it formed.<\/p\n\n\n

On the other hand, Ethiopian opal forms high in the mountains as a result of volcanic activity. Unlike Australian opal, it does not form in cracks but is found in volcanic ash in various forms. It is often fossilised vegetation or may contain such vegetation as inclusions. The most basic difference between the two types of opal is rooted in the porous nature of the Ethiopian. Most are also called hydrophane and can absorb water.<\/p\n\n\n

If Ethiopian opal (hydrophane) is soaked in water, it absorbs it and becomes crystal clear. When it is dehydrated, it returns its milky body completely.<\/p>\n\n<\/div>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

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\n \n \"\u0425\u0438\u0434\u0440\u0430\u0442\u0438\u0440\u0430\u043d\n\n <\/div>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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This is what the opal looked like before the experiment.<\/p>\n\n<\/div>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t

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Seconds after immersing it in a glass of water you can see how the hydration process begins.<\/p>\n\n<\/div>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t

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3 minutes later<\/p>\n\n<\/div>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t

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5 minutes later, it has almost completely become transparent.<\/p>\n\n<\/div>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

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6 minutes later the opal is fully hydrated and gas bubbles are clearly visible around it, displaced by the water.<\/p>\n\n<\/div>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t

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This is what the already hydrated Ethiopian opal looks like - crystal clear.<\/p>\n\n<\/div>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t

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Here is a before and after comparison with the other stone from a set of earrings with the same look.<\/p>\n\n<\/div>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

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1 hour later, the opal fully regained its original appearance and play of colors.<\/p>\n

If you are conducting the trial yourself, it is important to note that larger stones will require more time to hydrate (over 5-6 carats may take hours). Whether you choose Ethiopian opal or Australian opal is entirely a matter of preference.<\/p>\n

2. Colour<\/h5>\n

In nature, all the rainbow colours are found - green, orange, yellow, purple and the rare red. The value of the stone is determined by the dominant color, as an opal is almost never only one color of flare. There are secondary hidden colors that enhance and make more electric hues so the opal appears more sparkly thereby increasing its value.<\/p>\n

3. Color directionality<\/h5>\n

Opals are gemstones that drastically change their appearance depending on the angle from which they are viewed. Those that have strong reflections in all directions are the most preferred and multifaceted in jewelry. While the ones that are brightest in only one direction need to be provided with the position and type of jewelry so that they are visible most of the time. For this reason, it is difficult to find suitable opals for a pair with the same size, color and direction of glare. Dead spots or corners with no visible sparkle reduce the value of the stones.<\/p\n\n\n

4. Patterns <\/h5>\n

Some stones have a rare and unique patterns. The rarest and most expensive is called Harlequin. Other types may be Mackerel, Block, Lightning, Rainbow, and the most valuable in Ethiopian opals is called Honeycomb. If the opal has such an overall effect, its value increases.<\/p>\n\n<\/div>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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1.Opal Harlequin<\/p>\n\n<\/div>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t

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2. Ethiopian Opal - Honeycomb<\/p>\n\n<\/div>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

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5. Body colour<\/h5>\n

This metric was first adopted for the body tone of Australian opals, it is now accepted and applies to all. It is measured by a scale with 9 categories from N1 to N9, with N1 being considered the darkest and N9 the lightest.<\/p>\n