Real opal is a highly valued stone, and it’s never a good day when you happened to purchase fake opal because you didn’t know any better. Opal is an amorphous and hydrated version of the silica mineral, and this form has actual water content (anywhere from three to twenty-one percent). It is formally categorized as a mineraloid and can be found in rock fissures. Some of the rocks where opal can form include basalt, limonite, rhyolite, and marl.
The most significant supply of opal is mined in Australia, and it also happens to be the national gemstone of the subcontinent. What makes opal different from all the other gems that are usually collected is because of its water content; it tends to diffract light. Genuine opal comes in many colors, from white, yellow, orange, brown, magenta, etc.
The rarest of them all is the black and red hues, and you can be sure that red opals and black opals are the most valuable and highly prized in the jewelry world.
Colorless opal, called “potch,” does not show any hue or hint of any color, and thus it is called “common opal.” Precious opal, or the type used in jewelry, usually presents a most complex interplay of different colors. The interaction is due to the layering of opal molecules interspersed with the physical crystallization of the mineraloid.
Spotting Real Opal vs. Fake Opal
There are various ways to check if the gemstone you have is the real thing.
Check if the opal has a white or black lining or backing
First, check if the opal has a white or black lining or backing. If it does, then the combination of minerals is manmade, and depending on the number of colors you have, you may be holding either a doublet or triplet. Doublet or triplets are not necessarily faked, but you do not have pure opal. When opal is bound to become a double or triple, other minerals are used to complete the construction, and the adhesion is humanmade. Labs and manufacturers also use plastic backings for these constructions.
Check the side of the opal
Do you see thin layers that seem to have been adhered to one another? This is another case of humanmade fusion, and yes, you may have a double or triplet – again. Pure precious opal does not adhere to other gems. Another sign that you may be holding a modified or manmade opal construction is by inspecting the specimen’s back. Manmade or modified opal usually has smooth plastic backing. Real opal, because of its natural formation, will not have a completely flat and soft back. A small quantity of precious opal is usually bound to a sample of its host rock (also called the brown boulder) or some other backing material like glass or even vitrolite. The presence of any additional content that is adhered to the main opal body indicates hefty modification on the side of the manufacturer.
Check the surface of the precious opal
Genuine precious opal does not have a glassy look to it, even if it is a mineraloid. A seemingly polished finish probably means that the opal was capped or layered with another layer either to protect it or change its aesthetics. A variety of materials are used for capping layered opal constructions. Some manufacturers use plastic, while others cap precious opal with well-polished glass. No matter how polished the glass maybe it, it’s still glass, and it adheres to the gem. If you examine the opal from the side and you can see right through the first layer easily, you are likely holding a triplet.
There are also synthetic opals in the market. These can be difficult to differentiate from the real or natural ones because they are meant to simulate the naturally occurring mineraloid. A trained gemologist or an expert jeweler will tell you if the specimen is precious opal or a synthetic opal.
Another visual test that is interestingly accurate is the water fog test. Submerge the opal in water for some time and let the piece absorb some water. If you have a triple or doublet in hand, some of the water will begin to seep between adhesion layers (at least one layer of adhesion is present) and cause fogging. You will immediately see the seeping of the moisture between the sheets when you hold the piece up for inspection in the presence of intense natural light. Again, this doesn’t mean that the opal is faux; it means that it is not entirely made of the mineraloid.
Is it correct to say that synthetic opal is fake opal?
Not really, but it should be noted here that synthetic gems do not have the same value as mined precious opal, because they are grown in a lab.
Lab-grown gemstones are considered prime alternatives, and they are also much cheaper than naturally occurring gemstones. The same rule applies if you purchase other kinds of gems like diamonds. Lab-grown diamonds are decidedly less expensive, and they are chemically identical to the diamonds that occur naturally deep beneath the Earth’s surface.
Another thing you have to know about lab-grown opals is that sometimes, manufacturers add augmenting materials to them. So chemically speaking, when this happens, the lab-grown gem is no longer chemically identical to mined precious opal. The number one trait that lets you spot synthetic opals from the naturally occurring ones is their increased porosity. The density of lab-grown gems is also much lower than natural silica, which causes the final product to be more lightweight and more porous.
When scrutinized using a microscope, lab-grown opals will also feature super uniform color structures. Natural gems, precisely because they were formed by pressure and temperature fluxes, will have natural irregularities within their mineraloid structures. If you shine a synthetic opal with UV light, it won’t shine either.
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