As a fully fledged magpie it stands to reason that I would love opals with their bright flashing colours and shiny surfaces, but until quite recently I hadn’t realised just how fabulous they are; then something happened that really piqued my interest about opals, and my mission began.
A client bought an opal ring from us and a few months later she called to say the opal wasn’t an opal, it had gone clear so obviously it was synthetic. We were mortified, of course, and insisted she bring it back and let us replace it, no charge and a thousand apologies. We were really surprised and baffled by this little clear stone that we were sure was the real deal because we mostly know our gem dealers as being completely lovely people, but it did occur to us that this might have been a stone we bought on line from someone we didn’t know, and we’d been had. So we swore off buying from unknowns, replaced the opal in the ring, and decided to talk to our dealer in London about what had happened. Turns out that if she’d put her little opal ring on the radiator over night it would have been opal again in the morning! The opal was an Ethiopian opal, a hydrophane opal, which, as the name suggests, is all to do with water. But I’m getting ahead of myself…
I’ve always thought of opal as being an Australian stone and it is, but actually it appears in Roman references from 250BC. Apparently the referenced stones came from the Carpathian mountains and not from India as the traders claimed, so Europe was producing opal that long ago. At that time opals were considered the most precious stone with magical powers because the colours of all gems were represented in one stone. It was rare and difficult to get, but it was known. Then Louis Leakey, the well known anthropologist, discovered the first known opal relics in a cave in Kenya which he dated back to 4000BC. As no opals have ever been mined in Kenya, and these Kenyan opals were nothing like the ones found in Tanzania and further south, he concluded that they must have come from further north in Ethiopia, so the idea that opals have ‘only just’ been discovered in Ethiopia has rather been debunked. An ancient Chinese manuscript describes opals being found ‘far across the sea’ which turns out to be America, and indeed opals are mined in America, Mexico and South America and have been for centuries. More proof that opals have been players in the gem world for a very long time indeed.
Not only has the origin of opal been much discussed, but so has its name. The general concensus is that it comes from the sanskrit word ‘upala’.
But what are opals and why that wonderful play-of-colour (that is actually the technical term for it!)? Simply put, when water runs through sand it collects silica on its way. It runs into cracks and fissures underground or meets an impermeable layer of clay, and when it can’t go any further the water dries out leaving a deposit of silica. Over millenia this builds up and an opal is formed. The reason for the wonderful colours is that silica is formed of microscopic spheres and it’s the light diffracting off these spheres that makes the colour play. If the silica spheres are perfectly formed and packed then precious opal is formed, but if they’re haphazard then the dull opal that forms is called potch (also the technical term!), and it has no play-of-colour and no value.
Black opal Boulder opal
White opal Crystal opal
The most precious opal of all is the black opal for which Australia is so famous. It’s black because it’s formed in black potch which greatly enhances the brightness of the colours. Of course the value of this stone increases as the supply decreases, which it is. Then there’s boulder opal which also comes from Australia, and which forms in fissures in iron stone. Boulder opal has a lighter body tone than the black opal, and is clearer than white opal which, as its name suggests, has a milky white body tone. But none of these opals are actually transparent which brings us to crystal opals. These are transparent stones, or highly translucent anyway, and if you hold a torch behind the stone the light travels through it. All these opals have the famous play-of-colour that we so love, but Mexican fire opals, which deserve a mention here, seldom have play of colour in them, but they are in the other part of the colour spectrum – red and orange rather than blue and green. Interstingly, Mexican fire opals and Ethiopian opals are much more likely to have red, orange and yellow colours in them than the blues, greens and purples of Australian opals and this may be because both Mexican and Ethiopian opals are volcanic opals and Australian opals are sedimentary, but I haven’t actually read that anywhere… Ethiopia also produces fire opals which can be quite fabulous with their combination of clarity and play-of-colour which makes them so different from Australian opals. Ethiopia has become a very serious player in the commercial opal world, and all this in the last 20 years.
And so we’ve come full circle back to the Enthiopian – or Welo – opal which started this whole learning mission in the first place. I discover that hydrophane refers to the opal’s tendency to soak up a lot of water and dry out a lot of water, so probably what happened to the little ring is that it was submerged in water which it absorbed, flooding the silica spheres and preventing any light movement. Then, if we had dried it out on the radiator the water would have evaporated leaving the original composition of the opal intact. It was lucky the opal didn’t fracture, in fact, because they can absorb so much liquid that the stone often fractures with the pressure, but that didn’t happen in this instance and instead we just had a little glass cabochon to wonder about. The lesson in all this, of course, is to tell our clients exactly what sort of opal they are buying (now that we know a whole lot more about what we’re selling!) and to give them care advice. This wouldn’t be so important if we were using ‘doublets’ or ‘triplets’ in our work, because generally they are more robust, but even so a little lesson on that subject won’t go amiss I’m sure…
A doublet is a thin slice of precious opal which has a backing made of potch or sometimes obsidian or onyx. This greatly enhances the colours, of course, and means that you can have a substantial looking stone which is actually only half opal. A triplet goes one step further and has the black backing and then a clear domed cap on the other side, made either from glass or quartz or more modernly, plastic, which actually not only protects the little slice of opal underneath it, but acts as a bit of a magnifier making the colours look bigger and brighter. Obviously triplets are not considered to be precious stones and therefore should never be sold as such.
The fortunes of the wonderful opal have certainly risen and fallen (as an aside, in 1829 the opal fell on really hard times thanks to the novel by Sir Walter Scott called ‘Anna of Geierstein’ in which the Baroness of Arnheim had an opal with magical properties; when a drop of water fell on the stone it lost all its colour and shortly thereafter the Baroness died. People were so taken with the novel that they took this opal horror to heart and sales of opals dropped by 50% and took 20 years to recover!) but somewhere in the dim and distant past a clever magpie saw the opal for what it is, and this magpie has been completely smitten with opalitis.