Buying opals from jewellers or online sellers who do not specialize in opal
Buying opals for jewelry is a great decision because of the uniqueness and beauty of the stone which changes color when turned. But this practice is fraught with danger. In the past 30 years or so, clever marketers have found ways of producing gemstones such as rubies, sapphires, emeralds and more recently, opals that look not just like the real thing but are actually produced in a laboratory. It’s fine to own costume jewelry if that’s what you want but if you want the real thing, be careful of this practice. Unfortunately because opal is such a specialized gemstone, many jewelers themselves dont know much about it and are confused about its origin.
Buying opals that will crack or craze in a relatively short time
Opals and other gemstones such as emeralds have a tendency to crack if they are not from reliable sources. Emeralds are often treated with oil that can hide the cracks. Opal cracks are more difficult to hide but because opal is hydrated silica (meaning it has a percentage of water content.) This is fine, if the opal comes from the Australian outback deserts where the stone has been dried out over probably thousands of years.
Many opals being marketed cheaply are from coastal wet or mountainous areas where the water content is too high. These stones will almost certainly crack in time. You will need to make sure, even if your stone IS from Australia, that you have an international perpetual guarantee from a reliable supplier with a good reputation.
Buying opals that will lose their color almost immediately if you soak them in water
For a similar reason as the comments made above, opals from wet areas are also very porous which means that the surface of the stone can be like blotting paper. If you happen to wear your opal ring in the wash-up or the shower, it will almost certainly suck in the moisture and turn beautiful color into an ugly brown.
A good indication of this type of porous opal is that they are often faceted like diamonds and sapphires, rather than cut with a dome. This is not always the case but because they are often more translucent than opaque the stone presents better with facets. This is an immediate indication that it could well be a stone that will probably change color. It is said that if you put these stones in the sun for a while, the color will return but since they are often prone to cracking as well, this can be a risky procedure.
Buying opals without a high dome that are claw set
For claws to be closed onto a stone successfully its almost imperative that the stone is high domed or there will be a tendency for the hardness of the gold or silver claws to chip the edge of the opal. We are not saying that you should not buy stones like this because if they have been successfully closed without chipping the stone, thats fine. just look very closely and ask the supplier if the setting is perfect.
Buying opals without reading the small print to make sure it’s not ‘lab’ opal or man made
Even in some well respected online shopping sites, because the promoters are not opal experts, they don’t know anything about the differences between natural and synthetic opal. Often the individual promoters on these sites will hide the real identification of the opal within the body of extensive explanations and it’s so easy to read a paragraph and not even notice the ‘lab opal’ or ‘laboratory opal’ or ‘created opal’ identification. Sure, in MOST cases reputable sites will mention this but if you are not looking for it, it can easily be missed, resulting in you paying for something that looks OK but is not real.
Buying opals that have the same color on the front as the back of the stone
This is an excellent tell tale way of identifying a synthetic opal at a glance even if you don’t know much about the stone. It doesn’t ALWAYS apply because on occasions natural gemstones are the same color right through the stone but usually the back of the stone will have some imperfections or at least will have different patterns to the top of the stone.
So if you are buying an opal unless it’s from a reputable opal dealer, always ask to see the back of the stone as well as the front. If the back of the jewelry item is covered by gold and silver, it’s impossible to check, so don’t buy it unless you have absolute perpetual guarantee that it is natural. We say ‘perpetual’ because if the item is only guaranteed for a year, often the cracks or change of color will occur a couple of years down the track.
Buying opals that have a pattern that does not look natural
When synthetics were first invented they had a pattern that was obviously unnatural because the pattern ‘looked’ man made being too symmetrical. However this is not a good guide today because they have overcome this problem in the laboratory and unless you are an expert it can be very difficult from the foreground of the stone to tell the difference.
This just emphasizes again that unless you are dealing with a trained opal processor who gives an international perpetual guarantee, you really don’t know what you are buying and this piece of advice does not apply just to opal because jewellers shops nowadays are full of beautiful ‘rubies’ ‘sapphires’ and ‘diamonds’ which are man-made. As mentioned earlier, not that this is wrong. There is a market for them, as long as you know what you are buying and you are paying the right price for what is actually costume jewelry.
Just wanted to say a big thank you to Peter for his advice. I was considering buying a 1920s opal ring at auction and asked Peter how big an issue the crazing was, and thanks to him I was saved from buying a worthless stone! Much appreciated. – Catherine, USA