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Post by apesandmonkeys on May 28, 2013 19:39:21 GMT -5
Hello! Does anyone have any tips for tumbling Lapis (with a rotary tumbler)? And is it possible to be able to tumble lapis with Labradorite since they are both in the Feldspar family and have a similar hardness?---Or would their varying chemical compositions negatively affect tumbling together? I appreciate tips and advice. I seem to have an attraction to some of the softer, challenging stones =D Cheers!
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Post by paulshiroma on May 28, 2013 21:55:30 GMT -5
I haven't had luck with labradorite but others on the forum have done quite well with it. If you do a quick search you should be able to find some additional information. Someone is bound to have tried lapis at some point. Good luck! Oh, and good to meet you.
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mian
off to a rocking start
Member since February 2013
Posts: 1
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Post by mian on Jun 13, 2013 14:05:47 GMT -5
lapis is very nasty at polish stage. we do polish by hand [very time consuming].
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jspencer
freely admits to licking rocks
Member since March 2011
Posts: 929
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Post by jspencer on Jun 13, 2013 21:13:26 GMT -5
I have only done a small amount of it but I polished it in my vibe and it turned out great. I used Raybrite A polish.
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pameladragon
off to a rocking start
Member since October 2013
Posts: 2
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Post by pameladragon on Oct 28, 2013 17:32:15 GMT -5
I have a lot of lapis that my hubby sent back from Afghanistan. Some I slabbed for bas relief carving, some is still in chunks for carving, and some is in the tumbler now. I removed a batch from a soap burnish today and was not a bit happy with the finished polish. I am going to put it back in with more AlO and see if I can perk it up a bit. It is tumbling with some amazonite collected locally, which actually looks a lot nicer!
Any suggestions for improving my results? I use a 3# rotary and have a few of them with dedicated drums so grit mixing is not a problem. I also have a batch going into 120/220 right now, lapis, amazonite, and locally collected unikite. I mixed the chunks up good, small to large and they look good right now from the stage.
Thanks! Keep looking down....
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Post by 150FromFundy on Oct 28, 2013 20:16:08 GMT -5
Lapis is a rock composed of many minerals. Blue lazurite (soft), blue sodalite (soft), yellow pyrite (a metal), white calcite (soft) and black biotite (flakey) or hornblende (brittle). There may be a few others, but you get the idea. Lapis is a combination of many different minerals with different characters. It will grind and polish well on diamond disks, or wheels. It will not tumble well due to the varying hardness of the individual components.
A vibe tumbler with 90% ceramics and 10% lapis may improve the odds, but the lapis will be prone to polish residue as it tends to become pitted from the tumbling action.
If you have luck with this tumbling "nightmare", or "challenge", please post your story.
Darryl.
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pameladragon
off to a rocking start
Member since October 2013
Posts: 2
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Post by pameladragon on Oct 29, 2013 14:23:01 GMT -5
Thank you Darryl! I think I will just do each piece by hand with my flex-arm then or touch up the dull spots on the flat lap. I had no idea they would be so challenging. We have gotten an "orange peel" look on pieces polished on a cabbing machine, that should have tipped me off!
Pamela
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Post by apesandmonkeys on Dec 6, 2013 23:53:46 GMT -5
Thank you for the suggestions! It seems like a lot of my favorite rocks that I hope to polish are best hand-polished in some form.
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SirRoxalot
freely admits to licking rocks
Member since October 2003
Posts: 790
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Post by SirRoxalot on Dec 8, 2013 9:17:06 GMT -5
Lapis isn't in the feldspar group, it's in the sodalite group. As noted above, it's a mixture, or it might be something else altogether, like afghanite.
Personally, I wouldn't tumble it, what with it being one of the most valuable gems the average cabber is ever likely to cut.
I'd suggest tumbling it as you would sodalite. Don't mix it with other stuff, and use lots of pellets for padding, thicker slurry, slow your roll if you can.
Polishes fine via diamond cabber and AlO on felt.
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Jasper-hound
starting to spend too much on rocks
Member since June 2010
Posts: 208
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Post by Jasper-hound on Dec 15, 2013 11:39:56 GMT -5
To hell with labradorite!!! I will never try tumbling it again. RE Lapis, I have never tried tumbling it. High grade lapis is too valuable to tumble, and low grade lapis probably won't shine up.
~Hound
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