There is a HUGE amount of somewhat arcane opal terminology; so we’ll start with the most common point of confusion and work our way down to the more complex.
WHAT IS THE DIFFERENNCE BETWEEN A SOLID OPAL, A DOUBLE OPAL, AND A TRIPLET OPAL??
A SOLID opal has no added man-made extras: it is simply and only, pure, natural solid opal.
A DOUBLET opal is a thin piece of opal, glued onto a black (or dark) backing piece; which enhances the beauty & strength of the natural opal. In other words: the top of the gem is pure opal; the bottom is a different material.
A TRIPLET is similar to a doublet, but has an additional quartz or hard glass top which greatly magnifies the colours of the gem; as well as protecting the somewhat fragile & thin (very!) slice of opal. In this case, the opal is in the middle of the gem; with a dark bottom below it, and a quartz top above it.
The upside of doublets and triplets is that we can use the less valuable thin material we always seem to find; whilst making beautiful gems that are not very expensive.
The downside is that the glues used in the construction of doublets & triplets is susceptible to soaps and detergents: which will sometimes cause the laminated layers to come apart.
You have probably heard about opals losing their colours: well…. mostly it happens when people wearing doublets or triplets wash the dishes with their rings on; or shower whilst wearing their pendant, earrings, etc . If your are the owner of a doublet or triplet, just make sure you don’t dip them into any soapy water; especially the stronger detergents. The water doesn’t affect the opal: it is the soaps and detergents that do all the damage. Also, it is a common fallacy that solid opals absorb water, oil, or grime which causes them to lose colour. With very rare exceptions (Ethiopian opal is very absorbent for instance) THIS IS NOT TRUE! What DOES cause an opal to sometime “lose” colour is the fact that you’ve been wearing it for donkey’s years, and it simply needs a quick repolish. Opal being a hardness of 6 to 6.5 on the Moh scale (versus diamonds at 10) means that it needs to be repolished every 5 or 10 years; depending on how often you wear them, and what kind of setting it is in. We offer a re-polishing service: with a flat rate of $A10 plus postage for any opal in any setting.
ENHANCED or TREATED OPAL.
There are many different ways of enhancing gem opals. Firstly, let me explain how & why the enhancing treatment works.
There are SOME opals which have a certain degree of porosity, which enables the gem to absorb a small amount of liquid. As most enhanced gems start off with a light body tone (also known as base colour) The type of opal most commonly enhanced in Australia is the matrix from Andamooka; which usually comes with a white or light grey/brown base colour. By heating it in a solution of sugar and water, and then treating it with sulphuric acid, we are able to noticeable darken the base colour of the gem material (not all material “takes” treatment; which is one of opal’s many mysteries)
When the base colour is darkened, it has the effect of reducing incidental light: because the darker material doesn’t reflect as much light as it did beforehand. The has the beneficial effect of making the colours THAT ALREADY EXISTED IN THE GEM stand out more: hence the term “ENHANCEMENT”. A lot of people think that enhancement actually makes the colour….it does not….it simply enhances that which is already there.
Some treatment of the more porous material, especially that from Queensland known as “Rainbow Rock”, is carried out using a simple vegetable oil treatment: put the rocks in a potful of vegetable oil and cook until the oil gets hot and starts burning…..let all the oil burn away (carbonise) and HEY PRESTO!!! Darkened opal that looks a whole lot better than it did an hour ago.
Most of the enhancement treatments are permanent: once the carbon is in the gem it can only be removed by strong acid treatments.
A high percentage of Ethiopian opal is extremely absorbent: which means that you can soak it in food dye for a few hours; take it out and let it dry in the sun, and Hey Presto!! Green opal! Blue opal! whatever colour food dye will work. This process is reversible; unlike the carbonisation treatments.
This subject has more fallacies attached to it than the Loch Ness monster.
Because opal is a hydrated silica (which means that the silica which eventually made the opal was carried to that position by water movement) the opal invariably contains a small percentage of water. The more water remaining in the opal, the bigger problems you will have with cracking as the gem dries out: because loss of water causes the opal to shrink slightly. hence it cracks, or “crazes”; as it is sometimes called. Fortunately for us, our Australian opal mostly has low water content; from 2 – 8% which is as dry as it will ever get; so the gem will not crack or craze. Opals from other sites around the world have huge problems with crackiness simply because the water content is way too high. The beautiful black opal from Virgin Valley in the USA is sold in small capsules filled with gelatin to stop this drying out process. Indonesian opal is extremely cracky; often cracking on its first day after mining. Ethiopian opal also has a very high percentage of cracky opal (water content in these 3 opals varies between 10% and 30%….way higher than our Australian gems)
The reason for this difference in water content is mostly because of the differing geology: most of the really cracky opal is from a volcanic environment where the opal formed extremely fast, hence lacking time for it to solidify & dry out. On the other hand, the Australian opal is mostly sedimentary; which involves much longer periods of time (from 50 million years ago to 105 mya) This extra time involved in the opal’s formation caused a harder gem; with a much lower water content.
If you store your gems in a cool place, your beautiful Australian opal will remain beautiful for a VERY long time. Like all reputable opal dealers, we guarantee that our gems will never crack: and in the unlikely event of one doing so, we offer a 100% money-back guarantee.