Lapidary / Gemstone Community Forum

I've got an old Alka-Seltzer jar full of opal chips from Mexico. So, how does one go about 'cutting' these tiny pieces? Is it possible to even cab these things, or are they just to look at? Many pieces have some good fire, I just don't know how to go about capturing it for a jewelry setting. Do you set the chips in some sort of backing material like resin? I'm vexed by these little beauties.

These require backing and a quartz cap in many cases. After the high and low spots have been ground off the opal to produce a flat plate for capping they are often very tiny and really not worth the effort.

It all depends on the size and shape of the "chips."  If they're very small but bright the best use is probably inlay or embedding in plastic.  If they're large enough to cut as cabs, orientation of the best color play to the top of the stone is the most challenging element.  Many times the color play is just on a narrow edge or is situated on a very thin part of the rough, making cabbing impossible.  Much Mexican opal is also quite unstable and is subject to crazing after cutting. 

It's hard to give advice without seeing the stones in question.  A few pictures would help.

   

I also have a lot of 'chips' laying around.  Is there any trick to embedding this stuff into epoxy without ending up with lots of bubbles visable?

Greg, I think most of the commercial embedding is done using vacuum to pull the bubbles out.  I used to embed little turquoise chips in Epoxy 330 for certain jewelry pieces and found that gentle temporary heat makes the epoxy more liquid and allows bubbles to move to the surface and "pop."  Too much heat for too long causes the epoxy to set up, of course. 

If you have any that face up with enough mass behind them in that orientation you can cut them using a finishing nail or toothpick or small dowel as a dop. As already mentioned in a previous reply, the Mexican might be fragile.

Just like cutting any opal - if it survives the process it's a great thing. If not, don't be too surprised or disappointed. Drilling the end of a dop stick and gluing a finishing nail in the hole will give you a good shot at being able to work small bits.

There's a thread called "Very Small Opals" on here, but the photo has been deleted. If I find it in my archives I'll put it back up here.

If you want to thin epoxy without heating it, try thinning the epoxy with denatured alcohol. If you thin at an amount of 1/3 resin, 1/3 hardener, and 1/3 alcohol you will get a water consistency.  The best way to mix it is with a plastic medical cup calibrated in different measurements. Try adding the alcohol slowly a little at a time to get the right consistency. When you add the alcohol, the stuff will turn cloudy and then clear as you mix it.

I started my whole hobby with 3 of these types of opal jars. If you are careful you should be able to get many cabs out of a jar. You will have to study each piece to see how to cut it effectively to get a stone out of it, but with careful thought you should do well.