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[ileney]

Is there a reason why you can't make an opal doublet rather than a triplet from thin rough, assuming you can hide the seam in the setting? Will it craze or something?I think the visual quality is better as a doublet, but found I had to grind the opal part super thin on some pieces to bring out the color. Do I have to top it now, and if so, why?

[55fossil]

    You do not have to put a quartz cap on it.... but it will probably craze and crack with time if you do not.   THIN:   With the vast majority of Spencer opal you want to cut your opal as thin as possible. The hard part is judging which side of the opal will be the top... why????

One common way to make triplets of good grade spencer opal.

   After finding your layer of fire in the opal you need to cut away all the waste from the bottom and sides.
   Glue the basanite to the bottom of your opal. The basanite needs to be as close to the opal fire layer as possible.
   Grind the top of the opal down to less than 1mm, the thinner the better to get the fire to work.
   Some of the best cutters literally leave less than a few sheets of paper as a thickness of the opal before capping it. That is all you need before putting a quartz cap on it. Most, but not all Spencer opal has a fire layer that is best in extremely thin layers. Thicker layers look cloudy.

   The BEST Spencer opal can be cut as solids or doublets and be awesome and not craze.  This is the gin clear opal with fire in it that looks like Australian Fire Opal..
   

[lithicbeads]

I have seen opals set in a drawer for 16 years , getting checked each year and then crazing badly on the 16 th year. A triplet will help and you can make them low  with thin backing and a cap that you keep a very low dome on .

[hummingbirdstones]

Both of these are great answers.  If you're using Spencer, then I'd cap it just so it doesn't craze and also for protection of the thin opal layer.  If you find a really nice piece of Spencer that has really nice color without being paper thin, you can make a doublet out of it.  Vince found a piece with nice color that was thick enough that he was able to cut a solid out of it.  Hasn't crazed yet, but you never know.

[ileney]

Thank you so much for the great answers. This is very helpful. I started a whole big batch of doublets and triplets, and I think most may end as triplets.

Spencer:  I now have 2 large stones that I bought. I've started to cut them up. It looks like I might get one or maybe a couple of solids, also should be able to get a number of doublets or triplets out of them. So far, the one large doublet I made was a total dud and the fire I saw when I glued it has mysteriously disappeared, so I may get much less than I thought.

Coober Pedy: I have nice Coober Pedy, but some is too thin to be a solid (and some are offcuts), so I was making doublets or triplets of those thinner pieces.  I may have made them too thin for doublets based upon your advice and need to cap them.

Lightning Ridge: I also have a couple black pieces of lightning ridge that are super thin but have amazing color, but only one is flat and the other two curve so I'm not sure what to do with those.

Crystal opal: And lastly I have two old clear Australian (I believe) crystal opal that are probably thick enough to be solids but they have so much multicolor fire against a black background, I'm wondering if it really devalues them to make them doublets? Because the color is so much more dramatic, I'm inclined to turn them into doublets. Does anyone have any advice on that?

[vitzitziltecpatl]

If you don't want to make crystal doublets you can use a black epoxy colorant, and then paint the back. Some folks in Oz used to use black nail polish. It would be an "enhanced" stone rather than a "constructed" stone, but with the kind of crystal you have it's worth doing.

The only other option is to put it into a piece of jewelry with a black backing behind it. Simulated opal backed with foil was common years ago, but in your case the color play in the opal would be natural and the stone itself would be unaltered. It would still be good to disclose that if the piece was for sale, but if it's just for you who cares.

[cabomoon]

I have a small slab of Honduran opal with good color on both sides. Plan to cap on side with clear quartz.  Should I consider making it a triplet for longevity sake?

[ileney]

Is it black matrix Honduran? If it's black matrix, in my experience, it doesn't need it; because it's a volcanic matrix with bits of opal throughout, I can't see what would even craze or flake.  (If it is solid or seam opal, I imagine the same things they told me about the other types of solid opal would apply, but don't know for sure.)

[vitzitziltecpatl]

Yeah, Ileney's right on track for the Honduran. The basalt matrix should never be a problem. The two biggest negatives for Honduran is that it usually doesn't take a high polish, and that it might have some little pinholes in the surface.

[hummingbirdstones]

ileney, I just wanted to make sure you understood that my post was specifically about Spencer opal.  Australian opal will make fine doublets without a need to cap them.  I made a LR doublet out of a little piece that wasn't big enough to cut a solid.  Just glued it on a piece of black opal potch and it worked fine.

Your crystal opal I would not cut into doublets.  It is way more valuable as a solid, especially if it has that kind of fire.  Any of the methods he mentioned will work to blacken the back of the opal to make the fire pop.  My favorite thing to use is flat black spray paint that is for painting your grill.  I want to say it was Rustoleum, but I'm not positive on that.

For your 2 LR blacks that aren't flat, maybe you could imbed the curved bottom is some black resin to make an even bottom and then cab them?  Just a thought on that.  I've never tried it, but I don't see why it wouldn't work.

[ileney]

Thank you again! No, I didn’t realize Spencer and other white opal would be different, so thank you for clarifying. I have a bunch of coober pedy doublets that are pretty thin but if they do not have to be capped, I can hide the seam in the bezel and they look nice as is. Yes, I could embed the LR black curved pieces in black epoxy, but then you can’t see the natural back was black to start with (not sure if that matters).

As far as painting the back of a solid (not doublet) crystal opal black, doesn’t that have to be disclosed? What would you even say? Back of opal has been painted? Can you just paint the setting?

[vitzitziltecpatl]

Yeah, Ileney, painting the back of the stone or putting it in a blackened setting is something you'd want to disclose.

Re my comments a few posts back - you'd just call it an "enhanced" stone with an epoxy coating on the back if you did it that way. If you blackened the inside of the setting you could say the stone is natural and unaltered, but that the setting behind the opal was darkened to show all of the opal's natural beauty.

Sometimes with crystal opal you can "frost" the back of the stone by leaving it at something like a 220 grit finish, and that alone will improve the visibility of the color play. Then it hasn't been altered at all. It just wasn't polished to the same level as the face.

[hummingbirdstones]

What Vince said.  I should have said that in my post.   

You would have disclose the epoxy back if you put those LRs in some, too. I would just call them opal doublets.  It doesn't matter what the back part of doublet is made of as far as I know.

[ileney]

Ok, will do, thank you! I’ll post some of them when I finish them all.

[Opal Mike]

Hi, firstly I must apologise for not answering your last question to me in October 2016. Unfortunately my health was not good at that time and I was unable to do much for a long time.....indeed this is the first time I have logged back into this forum.

In regards to your doublet question; I can’t answer to your Spencer Opal, but can in reference to Coober Pedy material.  I have produced many hundreds of thousands of doublets for Asian wholesale companies over the years. For their purposes I slice solid Opals on my slicing machines to .7mm in thickness (doublets), and as thin as .15 for triplets...that’s 4 slices or 4 triplets to the millimetre of opal thickness (blades are .1mm thick, spaces .15mm).

The rough material is generally very good quality, healthy opal, ranging from crystal based reds and green orange to greyer or milkier based material with good colour. It is true that the milkier or whiter the base of the opal, the thinner it needs to be to get that darker kicky look, although the best, really dark flashy doublets come from the crystally based rough.

I cut a lot of really nice doublets for our own jewellery. My own material, I slice the opal much thicker; 1 mm for smaller stones and 1.2mm for larger. I slice black obsidian for the backing at 2mm for the smaller ones, and up to 2.5 for large ones. These finished doublets are a premium product with the opal content being around 30% of the finished stone.

I use ultra violet glue in my commercial setup which can be achieved without spending too much (I built the light set up myself)....the expensive part comes in the commercial fume cabinets that I do all my work in, due to the volume of stones I cut.

The obsidian I use is beautiful, and comes from Mexico. It is almost opaque sliced at 2 mm but when held up to a light source lets in a little bit of light, which is important as I don’t use any paint or blackening agent apart from the natural blackness of the obsidian.

The finished doublets have a nice cab, and look very natural when finished; indeed when bezel set (rubbed in setting), are impossible to pick from black or semi black solids.


In my opinion well cut doublets are the best value for money cut opal for both the jeweller and the end consumer...they are durable and extremely beautiful.

Because I choose my rough carefully, the crack rate of my doublets (over 30 years), remains less than 1%, which is in line with my solids. My doublets are water resistant and solvent proof, and absolutely safe with the ultrasonic.

You asked a question about comparative values against solids...should I cut it into a solid or a doublet. My answer would be make the most beautiful stone possible. When I buy rough for doublets, I am looking for healthy high quality material that could be cut into solids or doublets. Sometimes I buy a parcel of really bright healthy thinner material. This can be great also. This material I lap each piece by hand if it is thinner than 2mm and often leave the opal as thick as 1.5mm if it is really good crystal, so I can get a really nice cab, especially for ring stones.

To all of you out there, please don’t believe thinner is better! I don’t personally like thin flat really dark doublets. They look too much like triplets without a top, and are less natural in look, especially the commercially cut boulder (ironstone) backed Chinese finished doublets. I also don’t mind it if the finished doublet is on the lighter side, so long as the colour kicks nicely, which it should if the opal is half decent.

Just a footnote on the obsidian. It took me a while to source the right rough, but it is out there. It needs to be black obviously, and not too translucent when lapped to between 2 to 2.5mm. To test it lap a piece to 2mm, dry it and put it on a newspaper page (writing underneath). It should look black and opaque. Then hold it up to the edge of a lamp or hold it up to a direct light source. If you can just see through it, meaning the obsidian is not totally opaque....that is perfect. You can also use fully opaque black obsidian (at 2mm), if you prefer that look...my advice would be to experiment and see what works for you. I use both depending on the rough opal.

I hope this is helpful,
Mike