Fail-safe ways to spot a fake
To the untrained eye, spotting the difference between a natural opal and a sophisticated synthetic may not be immediately apparent. The spectrum of artificial opals varies from the obviously fake to the hard-to-detect lab-produced. To help authenticate your opal jewellery, check out some benchmarked identifiers below.
Real opal vs lab created
Let’s begin with some clear distinctions. It is not technically accurate to describe a lab-produced opal as ‘fake’. Most lab-created opals are done in a way that mimics the organic process as closely as possible to natural opal formation but within a concentrated period. Synthetic, or ‘lab-produced’ opals possess nearly all the same chemical, physical and optical characteristics as genuine, mined opals. However, there does exist some lab opals that have been modified with additional materials and, chemically speaking, are not identical to natural opal.
In the 1970s, The Gilson Company was the first to develop a three-step process to produce a believable synthetic opal.
The three steps are as follows:
Step 1: Microscopic spheres of silica are created through precipitation.
Step 2: The spheres settle in acidic water for over a year.
Step 3: The spheres are then consolidated with a hydrostatic press, making sure not to disturb the stacked arrangement (this is what facilitates the opal’s play of colour).
Because a lab-created opal can be easily reproduced, it is less rare and, therefore, much less valuable than natural opal. Guidelines exist to protect buyers from being duped unknowingly into buying synthetic opals. Luckily, Australia is home to the world’s largest supply of natural, precious opal, and any credible Australian opal supplier will be able to provide proof of an opal’s origin and type.
How to spot a synthetic opal?
There are four primary ways to spot if an opal has been created in a lab. The first and most visible giveaway is the ‘lizard skin’ effect. Lizard skin is the effect of a systematic ordering of colour – the pattern presents within the colour blocks as ‘lizard skin’.
When you view a synthetic opal side-on, its colour structure will present as neatly lined columns, with the pattern appearing in a repeated uniform way through the stone. Genuine opal, when viewed side-on, will appear solid as it is not composed of different layers. Natural opal would not appear standardised from all angles.
Synthetic opal is more porous than natural opal. The density of a lab-produced opal is much lower than naturally formed silica comprised opal, which will feel more lightweight. If a synthetic opal is exposed to moisture for long periods or submerged underwater, you may be able to see the condensation or water build-up.
Another giveaway of synthetic opal is to hold it under UV light. You’ll find it does not shine like a natural opal does.
Synthetic Opal
Genuine Australian Boulder Opal
Ensuring your opal is genuine
Real opal will not be made of glass, plastic or resin. A genuine opal is a solid stone made of silica. Unless your opal is specified as a doublet or triplet, it should not have foreign material glued or fused to the back.
A high-quality opal doublet will have a genuine opal face with a man-made backing to add to the weight and substance. Doublets and triplets can also be referred to as ‘composite stones’ and can make excellent affordable alternatives. It’s important to be aware of the exact opal you’re buying – do your research to avoid being overcharged.
A notable marker of natural opal is the even spread of colour across the opal’s body. Colour play should be showcased by the opal when viewed from both the front and side. It should also be free of soot marks. A soot mark can indicate that the opal has been artificially enhanced in some way, either by a sugar or smoking treatment.
Composite Opal
Opal Doublet Side
Real opal vs fake
A fake opal can be easier to detect than a sophisticated lab-produced one. Fake opals include those that are made from glass, plastic or resin. An opal imitation will often have an overly shiny appearance, and the colour flashes will be repeated in an organised pattern. Turn it side-on, and a columnar structure will be revealed to you. Real, natural opals possess irregularities, which adds to the stone’s authenticity and beauty.
Glass opals can be produced in an array of colours designed to mimic the physical appearance of natural opals. There are two main types of glass used to reproduce fake opals. Slocum stone is a silicate type of glass that features flakes of iridescent film that replicate the play of colour seen in genuine opal. Opalescent glass is the other commonly used manmade glass. It possesses a sheen-like lustre that, to the untrained eye, may appear as genuine opal. Opalite is a type of man-made plastic with an opalescence effect and is sometimes used to create fake opals.
What about treated opals?
Sedimentary opals that are mined in Australia are much less porous than those found in other parts of the world. A natural opal that is particularly porous can be enhanced by either dye, smoke, sugar or acid treatment. Various ‘treatments’ are intended to alter the body colour of the opal to look like precious black or black boulder opals. A sugar or acid treatment is carried out by soaking an opal for a few days at a time in warm sugar water, followed by submerging it in sulfuric acid. The acid works to oxidise the sugar between the pores of the opal, producing dark-coloured particles and stains.
Australia is home to some of the world’s most exquisite and precious opals. To ensure your precious opal is the real deal, ask your supplier where the opal was mined. Your Australian opal should come with a certificate of origin and authenticity. The best way to ensure authenticity is to purchase your opal from an accredited supplier with gemmological qualifications.
Some of Australia’s most popular and respected opal mines include Jundah-Oplaville and Winton located in Queensland, Lightning Ridge in New South Wales, and Coober Pedy in South Australia.
Treated Australian Opal
Natural Untreated Australian Black Opal
The Opal Minded guarantee
A real, natural opal should always be accompanied by a statement of its origin. At Opal Minded, all our opals are natural, untreated, ethically sourced and majority are mined by our founder himself – John Bernard. You can discover more about where we mine our precious opals by visiting the Where Are Opals Found page.
We guarantee our opal jewellery and unset stones for life. Our gemmologists’ qualifications are from the Gemmological Association of Australia (GAA) and the Gemmological Institute of America (GIA). A Certificate of Authenticity validates the origin of the opal, its weight and type and provides a photograph that identifies it. Our valuers and gemmologists ensure our prices reflect a fair retail market price. Our solid opals are treatment-free, and a Certificate of Valuation by one of our accredited valuers confirms this in writing.
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