steve8852
off to a rocking start
Member since February 2017
Posts: 2
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Post by steve8852 on Feb 27, 2017 17:07:09 GMT -5
I was given some Brazilian quartz rocks for Christmas to tumble. I completed the tumbling from coarse grit to polishing and when completed the edges of the rocks are smooth but not polished. I've never had this happen before; the rocks have tumbled previously have been polished on all surfaces however they started out more rounded than the very sharp edges of the quartz rocks.
Anybody else experienced this problem? If so, is there a fix or a flaw in my process of tumbling? I tumble each step for a full week and have been very careful with not contaminating the polishing step with coarse grit and have tumbled many barrels of rocks successfully previously.
I tried to attached it a picture of some of the polished rocks to show the flat surfaces are polished but all the corners are smooth but not polished.
Thanks for any help!
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Post by adam on Feb 27, 2017 17:20:54 GMT -5
Welcome to the board, steve8852.
Your problem could be helped better with photo evidence.
Brazilian agates are very fun to tumble, but those agates with quartz crystals intermixed is tougher to get polished. This is because the crystal grains trap polish and leaves a white residue. Also, crystals break apart, sometimes leaving gaps in later stages because crystals broke up during tumbling. Nothing you can do but throw the rock back in coarse, or break it up into smaller pieces and tumble them like that.
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Post by Jugglerguy on Feb 27, 2017 19:18:42 GMT -5
Hi Steve, welcome to RTH. If you want to post pictures, you have to host them on a site like Flickr and then copy the BBcode here. The BBcode can be found after clicking the share button that is a little curved arrow. I can give you more details if you need help.
It's strange that you are having trouble with the corners. With some rocks, like obsidian for example, the edges get banged up more and get little tiny scuff marks. This is sometimes called bruising or frosting. Quartz often fractures if it's banged around too much. If the edges are smooth, but just not shiny, usually the opposite is true. With rocks that have large flat surfaces, sometimes those are the parts that are hard to polish, while the edges shine up nicely.
You mentioned that you ran each stage for a week and that there are sharp edges. Many of us here tumble our first stage for weeks or months, cleaning out each week. I like to get my rocks nicely rounded and completely free of holes and cracks before going to stage two. The rest of the stages can be run for a week or two each. In the first stage, I take out any rocks that look perfect each week and throw the rest back in with some more rough. I keep doing this until I have enough rocks set aside to fill a barrel for the next stage.
I should ask, are you using a rotary tumble or a vibratory tumbler?
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Sabre52
Cave Dweller
Me and my gal, Rosie
Member since August 2005
Posts: 20,487
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Post by Sabre52 on Feb 28, 2017 8:55:36 GMT -5
Crystalline quartz is actually pretty delicate and behaves much more like obsidian than agate. Those frosted edges are little scuffs and micro fractures from knocking together. Problem can be solved by running them with a lot of pellets and smalls as filler to cushion the load and by making sure the more angular edges are better rounded. In a rotary, a fairly full barrel will prevent the rocks dropping against each other as much too. Just got to prevent those impacts and just have the stones flow smoothy against each other. I like tin oxide for final polish on quartz crystal too just like with obsidian....Mel
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Fossilman
Cave Dweller
Member since January 2009
Posts: 20,711
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Post by Fossilman on Feb 28, 2017 9:57:59 GMT -5
I usually run mine with smaller gravel pieces and pellets,but run that material for two to three weeks on first stag.... Tough material..
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steve8852
off to a rocking start
Member since February 2017
Posts: 2
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Post by steve8852 on Feb 28, 2017 18:34:06 GMT -5
I'm using a 3 lb rotary tumbler. I appreciate the responses and help. From research and your replies I think the problem stems from the shape of the rocks stemming from them not being more rounded. I need to go back and run the coarse grit for about a month and for polish I need to add a step and use cerium oxide and tin oxide to polish instead of aluminium oxide. Thanks for the input!
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