jilly
off to a rocking start
Member since November 2010
Posts: 17
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calcite
Nov 10, 2010 15:42:20 GMT -5
Post by jilly on Nov 10, 2010 15:42:20 GMT -5
I got some pretty calcite chunks recently and would like to tumble them. I know they are exceedingly soft but was told they would be okay in a vibratory tumbler. However I want to round off the edges a little first. We don't have any hand polishing equipment. Could I put them in a rotary for a short time first to do this, and with what grit? Hours or days?
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calcite
Nov 10, 2010 17:46:38 GMT -5
Post by susand24224 on Nov 10, 2010 17:46:38 GMT -5
You can do it in a rotary. Use 120/220 grit (at most), add at least 50% ceramic shapes, and check after 2-3 days. This would be my formula, but I'm sure there are others. I also add soap for a quick thickening of water (cushioning), such as borax or shavings of Ivory. A final suggestion is to overfill the barrel, almost to the top, which impairs the action of the tumbler.
Susan
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tomcloss
starting to spend too much on rocks
Member since October 2008
Posts: 158
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calcite
Nov 11, 2010 23:18:53 GMT -5
Post by tomcloss on Nov 11, 2010 23:18:53 GMT -5
Calcite is soft so I would check it often. Another thing you can do for cushioning is to use Karo Syrup to thicken the slur. I use plastic filler in my rotary. But the big thing here is remember its soft and check it often.
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rollingstone
starting to spend too much on rocks
Member since July 2009
Posts: 236
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calcite
Nov 13, 2010 16:59:17 GMT -5
Post by rollingstone on Nov 13, 2010 16:59:17 GMT -5
I did some travertine (a form of calcite) in a 6-lb rotary tumbler a couple years ago and while I couldn't get a shine on it I certainly could round them. I can't find the original thread but if memory serves me right I ran them for week-long cycles in coarse grind, using 120/220 as my coarse grind grit instead of the usual 60/90. I used a LOT of plastic pellets to cushion things in the barrel (I think about 50-50 with rocks vs pellets), and filled the barrel up almost to the top so things couldn't tumble so much as just rub and slide past each other. Doing it that way, most of the stones were nicely rounded after 7 days, but the larger stones needed a second 7-day tumble in 120/220. I forget what I did after that, but I'm guessing about 5 days in 500 grit, followed by a week or two in aluminum oxide, but no matter, I couldn't get anything more than matte on them. Not sure if Harry still haunts these boards, but he suggested I try manually rubbing them in denim soaked with polish to see if that would put a shine on them, I still haven't tried that though.... eventually I will! Anywhere here's the rough I started with:  And here's how it ended after polish (but all the shaping was done in the coarse grind stage, using 120/220.  |
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calcite
Nov 13, 2010 23:01:48 GMT -5
Post by Hard Rock Cafe on Nov 13, 2010 23:01:48 GMT -5
Those are pretty! There must be some way to get a shine on them, but like my handle says, I only work with harder rocks.
Chuck
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Steve
has rocks in the head
Member since June 2005
Posts: 506
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calcite
Nov 14, 2010 13:57:38 GMT -5
Post by Steve on Nov 14, 2010 13:57:38 GMT -5
Sometimes you can get a shine the softer stones by hand polishing with a damp cloth with a bit of polish. Toothpaste worked up into a foam can be used as a polish, also you can just use your fingers instead of the cloth.
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Maybe you can post some pictures here