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Polishing Jasper Cabochons

Hi, I purchase some beautiful Picture Jasper Cabochons unfortunately they arrived with only one side polished. They are large so I will need to set them with cutout backs to decrease the sterling cost and show off the beautiful back sides. I have never polished gems. How do I go about accomplishing this task? Or is it something I should job out? If so any gem polishers you can recommend?
Thanks, Deb

Do you have a local gem & mineral club that offers lapidary classes? That might be a good place to start.

Short term I agree, find a gem and mineral club and someone to help you polish your stones. You might also try sanding through the finest grit that you have and then, if you have it, polish with Zam. It works on turquoise, but turquoise is a lot softer than most Jasper. You can also try to coat the backs with resin. I have cut and polished a lot of Jasper and they are pretty straight forward if you have the right equipment. Unfortunately, the right equipment is expensive and it takes time to learn how to use it. If you add lapidary to your shop and skill set, you don’t have to buy industry standard sized findings and stones. This opens up a whole new set of creativity horizons. Good luck…Rob

Great idea Danielle! We do have a local group! Thanks, Deb.

Regards,

Deb Haug,

Certificate of Jewellery Skills,

Alberta University of the Arts

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deb@gemrapture.ca

  **1-780-953-8234**

Div. of Create-Mode Inc.

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It’s difficult to get a good polish on flat areas. You’ll need a series of flat laps and a machine that runs them wet; the normal peripheral wheels used for polishing domed cabochons won’t work. After you’ve done one or two, you might decide that the extra sterling required to cover the backs isn’t such a big deal after all.

Thanks Andrew, that that was the method I thought was required. I appreciate your details, not going to waste time with the peripheral wheels. I found a few more that need that need attention too.
I will contact the fellow I know with the local rock club, I have seen his work.

Deb

Regards,

Deb Haug,

Certificate of Jewellery Skills,

Alberta University of the Arts

image003.png

deb@gemrapture.ca

  **1-780-953-8234**

Div. of Create-Mode Inc.

image002.jpg

It is not difficult to polish the flat backs with a Genie or similar wheel polishing setup. However, getting it flat to begin with is. I assume the backs are sawn flat, but not polished. Are there obvious saw marks left from the original cut making the slab? If so, getting rid of these will be the challenge, where a flat lap comes in. If these marks are deep, removing enough material to make them go away will make your cab less thick.

If you don’t have serious saw marks, you can easily polish the backs with the (typically) 6" soft wheels intended for final polish. They won’t take off enough material to compromise the flatness.

My fellow gem club friends routinely finish cabs polished in this manner. In fact I do have a flat lap at the end of my Genie, but once I get the backs past the 600 grit range, I take them to the wheels for polishing.

At our county fair, we have a very tough lapidary judge. He won’t take points off for unpolished backs, but if you want to win a blue ribbon, they’d better be polished. Next time you source cabs, ask about the backs if not disclosed, because many of us do polish the backs (and will say so in the listing).

If you enjoy designing with cabs, it would be worth it to seek out your local gem club, learn lapidary, and gain control.

Thanks Terry, I will try with the lap and some Zam. Good advice on requesting to view the backs, I slipped up on those purchases! Beautiful pieces though and I look forward to setting them with open backs.
Deb