johnnymac1969
starting to spend too much on rocks
I Like A Rolling Stone
Member since January 2016
Posts: 139
|
Post by johnnymac1969 on May 21, 2016 20:00:05 GMT -5
A friend of mine recently visited Martha's Vineyard and collected some Quahog shells. She said she got "a bunch", but that turned out to be only 5 or so small pieces. She wants me to try to tumble them. The broken pieces are already pretty smooth from the ocean waves. The whole-half piece looks relatively "new" and has not been smoothed out at all. I have never tumbled sea shells before so I did a little research. It turns out that most sea shells contain calcite, which I'm guessing gives them a Mohs scale of around 3? Has anyone here ever tumbled sea shells? If so, how fragile are they in a rotary and/or vibe? Would they survive a week of Stage 1 in the rotary? Can I tumble them with softer rocks like quarts, etc? Any advice/info would be greatly appreciated! Thanks, John
|
|
|
Post by Jugglerguy on May 21, 2016 20:34:29 GMT -5
I've never tumbled shells, but I tumble Petoskey stones. They're also made of calcite. I would try tumbling them in a vibe with corn cob media and grit. I'd start with 500AO and see how it goes. I've used the Rock Shed's corn cob and also Hartz brand pet bedding and I don't notice a difference, except that the pet stuff is a lot bigger. You might be able to do 220 in a rotary before that, but I'd only run them for a day or less before checking on them.
If anyone gives you advice who has actually tumbled sea shells, ignore everything I just said and do what they tell you to do.
|
|
johnnymac1969
starting to spend too much on rocks
I Like A Rolling Stone
Member since January 2016
Posts: 139
|
Post by johnnymac1969 on May 22, 2016 6:37:35 GMT -5
Thanks Rob!
|
|
|
Post by Peruano on May 22, 2016 8:19:45 GMT -5
Well, I sorta have. I processed some very special shell remnants in a vibe tumbler with some success. 1. Most shells are fairly fragile except for the central or basal thickest parts. Expect them to change shapes and perhaps even break on edges unless you have them well buffered. 2. Most are somewhat soft and hence I'd stay away from grits in the 60-100 range and be prepared for your slurry to stiffen with a spackle (plaster-like) consistency unless you monitor water carefully. So if processing wet, check them often. 3. Expect them to move quickly through the steps. Again check frequently. The advice to do the dry is probably the safest approach. The shells I tumbled were the central cores of large shells already tumbled naturally and in my estimation very hard compared to other shells. I'm not sure whether I'm spread urban myths or poorly documented cautions, but the dust of shells is supposedly quite toxic or at least irritating to the lungs if ingested. Thus my advice is to perform cleanups carefully, wash and rinse thoroughly, and vacuum up any dust that may remain after everything dries. Believe it or not this is an oft repeated caution but its hard to find real data on toxicity and I suspect its more like the silicosis warnings against breathing all kinds of rock dust. I avoided most shells because I deemed them of little interest, but the shells you are considering have color and hopefully a structure that will allow you to do something with them besides turn them into powder. Good luck. Here are some of the shell remnants I tumbled - not necessarily the best but . . . they were at hand. Tom
|
|
|
Post by beefjello on May 22, 2016 15:23:32 GMT -5
Hi johnnymac1969 Here's one I received from a member here many years ago and a description of the process he used Normally it is solid purple and white, but sometimes the purple is in layers. If anyone decides to work with Cohogs shell; you should know that the dust is unhealthy for your lungs; may cause lung cancer or something bad. I work with it on a cabbing machine with a mask and then tumble for the final polish (500 then A/O sometimes 120/220). I put them in with jaspers and agates; it is pretty hard stuff.
|
|