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The Kitchen-Table Opal Triplet
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An opal triplet is a composite stone made up of three layers. On the bottom is the backing layer, of black basalt or other dark stone, or perhaps of black architectural glass. In a pinch, I've even used dark welder's shield glass. In the middle of the
sandwich, a very thin layer of precious opal, which in turn is covered over by a protective "dome" of clear quartz. A finished triplet looks like this:
There is just a hint of stigma attached to the "triplet" designation, a spillover from other precious stones where making a composite is usually an outright fraud. My friend Claudette the goldsmith, for whom I often cut stones keeps telling me that,
"Well, you know, say what you will, for me, a triplet still doesn't compare to a real stone".
Since she says quite explicitly "say what you will," that is to say, it doesn't matter what comes out of my mouth, she won't be listening to it (I have by the way put this to the test: she's telling the exact truth!) I've given up saying anything at all.
I just keep making my opal triplets and put 'em in the display case. Occasionally Claudette will come over and marvel at the brilliance of their colour flash until it dawns on her that these are in fact, all triplets, and she says "you know, say what you
will...". I for my part just keep quiet and smile because I don't think she realizes that we've done this dance before. I doubt I'll be making a convert of her any time soon. Not with listening skills like hers.
The fact that even a professional goldsmith will turn up her nose at the word "triplet" indicates that between the stone side and the metal side of the precious professions there lies a gap both in understanding and in attitude toward materials. The
goldsmith, while he may be stone-savvy, probably is so to a limited extent. He will have heard of a variety of treatments, triplets, doublets, foilings, dyeings and such designed to fake high value precious stones, and so will regard the word "triplet"
with mistrust in any context.
And yet it is the pride of the stone cutter to develop the features of the stone which nature gave him. Seldom is the gift conveniently presented. Seldom is the stone perfect. Here there is a flaw to be cut out. There an inclusion. Should it be cut out
also or should it be centered on the finished stone and become part of the design? The hidden gift has not only to be uncovered, but also to be wrestled for, like Jacob wrestling with the angel. We don't do it because it's easy. Precisely in the fact that
it is difficult is where the appeal lies. Why else would we do it if not to wring a reward out of recalcitrant rock?
Making a triplet to get the best out of a piece of rough opal falls squarely into that context. There is pride in the process, but the goldsmith, who does not have to tease forth his material in anything near the same way, may easily overlook that, not
out of skepticism or even malice, but simply from innocent unfamiliarity with the more intimate details of stone cutting.
Three factors speak in favour of making a triplet. Opal is costly - a triplet gets maximum use from the material. The colour layer in the rough is often very thin. From such a layer of colour which would be impossibly fragile to work or to wear as is, a
composite stone triplet suitable for jewellery use can readily be made.
Play of colour is opal's distinguishing feature, and opal in a triplet shows its colours to their very best advantage. In fact, in some cases, the colour of a stone which is sufficiently thick to warrant cutting as a solid stone is dramatically improved
when it is cut as a triplet. There's nothing counterfeit about any of these purposes. As far as I am aware, only for opal is making a triplet a traditional and fully legitimate technique. Perhaps for ammolite also, but that's so recent a stone on the
market that one can hardly speak of a cutting tradition.
Right then. After this much philosophy let's get some dirt under the fingernails. The nice thing about making triplets is that if you have opal rough and a few basic tools, you can do the whole thing on the kitchen table. If you're really skilled at
improvising, you don't need a saw, or even a cabbing machine. But both help, and we will be using them.
Usually the opal rough you buy in a small bottle for, say, in the 30$ (CDN) an ounce range consists of chips of white opal somewhere between a dime and a quarter in diametre - often smaller, seldom larger. These are chips that a professional cutter
refused, there not being enough saleable, good colour material in them to adequately compensate him for the time he would need to invest in cutting them. The key here is "adequately compensate." There may well be colour in the rough. It may well make an
excellent stone when the colour is carefully worked free. But if a professional cutter is going to spend three hours doing that, he needs to be sure the result is going bring a hundred dollars or two. As amateurs, we don't have that problem. We do it
because we enjoy it. Thus our rough opal is not necessarily trash, but is almost necessarily time-consuming.
Illustration two shows a chip of opal rough, say about the size of your little finger nail. The top and bottom halves are milky, uninteresting, but there's a thin seam of colour running through the middle. For drawing convenience I've made this seam
unrealistically easy to work with. It's not often they're so uniformly thick, or lie so nice and flat within the stone. Often the colour seam will dip or maybe fork into two.
It's that colour seam that you want to isolate in the form of a thin wafer. There are lots of ways of doing it. You can grind down to the seam from the top, or you can grind away the bottom, or, if you have a thin slicer saw, you can saw away the potch on
both sides. But for the purposes of this story, we're hand grinding on the kitchen table.
Onto the kitchen table a newspaper is spread out, and on that goes a piece of plate glass, say one foot long by 6 inches wide to give a good working surface. The plate glass will be the underlay on which the grinding is done. Glass 1/4" thick is good,
being thick enough that it doesn't bend much and is not so fragile.
Put down on the glass just a small knife tip of 220 grit abrasive, moisten that, and, holding the opal between your fingers, rub it round and round and back in forth in the grit slurry. At first the opal chip will bind up a bit, catch and dig into the
glass, but once its rough edges have been removed, it'll grind quite readily. You'll be surprised how fast it wears away. Check periodically to see how close you're coming to the colour layer. Once you hit the colour, stop grinding. Now you've got to
think and make decisions.
Check the colour layer. The aim is to develop the biggest possible area of colour which of course gets you the biggest opal wafer and thus also the biggest finished stone. In illustration 3 you'd probably get a larger flat area of colour if you ground
down to plane A than you would grinding to plane B. Depending on the thickness of the colour layer, and on its shape, it's not that difficult to grind all the way through it, as in illustration 4, where the colour layer is saddle shaped. Needless to say,
this is not a happy event.
Once you've got the maximum extent of colour exposed, the next step is to cement on either the top of the bottom, the top being a wafer of clear quartz, the bottom the dark basalt or black glass. I like to cement on the bottom, the basalt, first, because
that way when you continue the hand grinding to remove the excess on the other side of the stone you can watch what happens to the colour layer as you grind closer and closer to the basalt.
Initially I was afraid I'd grind away too much of the colour, so I'd leave the wafer in the middle of my triplets fairly thick. The trouble with that is, with the opal we hobbyists commonly use, the thicker the opal layer is, the more of the white base
colour stays in the wafer. The result is a triplet in which there's enough white left that the opal colours appear as if through a cloudy, milky veil. The thinner the colour layer on the other hand, the more dramatically the colours stand out against the
black backing. So, after a bit of experimentation perhaps, don't be afraid to grind the opal down to a very thin layer indeed, in some cases almost as thin as a sheet of paper. Cementing the opal to the black backing first allows you to check the effect
as you work.
Just to recap, the procedure I use is to grind the opal chip on the glass until the maximum area of colour is exposed. That side of the chip is then cemented to the black backing. The backing also should first be ground flat on the glass sheet grinding
lap. You don't need to go any finer than 220 grit, and that's still rough enough to give a good gripping surface for the epoxy.
For cementing, I use epoxy 330. It dries clear and strong. Prior to applying epoxy the surfaces to be glued should be cleaned with acetone, since any finger grease is harmful to the durability of the bond. Bubbles are a constant hazard, though, and here
I've found warming the stone, the quartz top and the backing helps make the epoxy thin and runny. I use an old restaurant coffee warmer, and lay a slab of three quarter inch granite upon the heating element. It takes a while to warm up, but holds heat
nicely. The chip should be lowered with tweezers onto the backing at an angle, and then gradually brought down flat, somewhat like laying a book down slowly on the table. This procedure also helps prevent bubbles.
While all this sounds very simple and matter of fact, working with epoxy on an opal chip half the size of a dime is not a lot of fun. No matter how careful you are, the epoxy gets on your fingers, your tools, and the working area. Epoxy covered tweezer
tips make manipulating the opal chip a procedure to be accompanied by a background music of curses. Keep a bottle of rubbing alcohol handy to unstick fingers and tools.
The glue doesn't need to be epoxy. Canada Balsam is used, as are stick shellac and even dop wax. You'd think the dop wax would leave a telltale colour, but the sticking layer is so thin, it's transparent. Each of these adhesives is made to flow by heat.
Thus a triplet made in this way is more susceptible to coming apart if the piece of jewellery it ends up in is subjected to undue heat. Also, Canada Balsam and stick shellac are more difficult to come by than epoxy.
Once you get confident you can glue up a number of opal chips on the same backing, and then grind them all down in one go. This saves time but lessens the control you have over each individual stone, since all will be ground to the same thickness.
Assuming you're still working with a single opal chip, once it's ground down to its final thickness the wafer of clear quartz is cemented on top in the same way as described above. Clothespins and bobby pins help hold things in position, gentle heat from
a heat lamp speeds curing. What you have now looks like this:
The finished sandwich is now treated as any normal cabochon would be, shaped, domed and polished. I always go for maximum area of opal, which means that the finished cabochon stones are not necessarily oval, since in order to get that standard oval shape
I'd have to sacrifice some of the opal. After all that work putting it together, it seems a shame to grind it off again. The stone should be cut with a comparatively low profile. Too high a dome acts as a magnifier and makes the stone look unnatural, and
also, looked at from the side, the high dome is transparent. The finished stone is bezel set, with the bezel covering the joint.
And that's really all there is to it. An opal triplet should always be identified as such. It's not uncommon for such a stone to be sold to an unsuspecting customer simply as "opal" without any elaboration. That indeed is unethical. Claudette's "say what
you will" notwithstanding, when you marvel at the brilliance of its colour flash yourself, you'll know an opal triplet is a stone that is as "real" as any
other.
Copyright 1997 by Hans Durstling
Opal triplet pendant courtesy of The Opal Mine.
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Copyright, 1997 by Hans Durstling
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Hans Durstling is a freelance writer, jewellery maker and stone cutter living in Moncton, New Brunswick, Canada, near the zeolite, agate and amethyst collecting areas on the Bay of Fundy. His stories, reviews and commentaries have appeared in Canadian
Geographic Magazine, The European, Toronto Globe & Mail, Canadian Mineralogist, Mineralienwelt, Rock & Gem and many others. He now works primarily in corporate & industrial writing explaining complex scientific and technical products and processes to
layman readers, and writing & narrating corporate & technical videos. A considerable portion of his time is taken up with the constant battle to keep minerals and gems ("the hobby that got out of control") from taking over entirely.
Hans can be reached at sinico@nbnet.nb.ca.
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