(no subject)

[the_rck]

Sedimentary rocks do *not* do well in the rock tumbler. This is obvious once I think about it, but I didn't think about it when I dumped in all the rocks I could scrounge around the house in an effort to reach the 8 oz. minimum. Now I have to try to remember my eighth grade geology lessons well enough to be sure I'm not putting such rocks in the tumbler. I expect I'll manage, but why on earth didn't I think of it before?

I'm starting to look into buying more grit for the tumbler. Scott thinks I can find it cheap in small quantities, but I'm not so sure. I've done only the most superficial search so far (I don't really want to run the thing again until we can put it outside, and that requires warmer weather) and haven't yet found grit sold in small quantities except when it's packaged with other stuff that I don't want. I may simply have to bite the bullet and buy it in bulk. (For relative values of 'bulk.' What I've found that's affordable involves one pound each of the first two types of grit and a half pound each of the third and fourth.)

Now that the weather is starting to improve, Cordelia and I are starting to pick up interesting looking rocks with an eye toward polishing them. I think we need to experiment to find out what works and what doesn't. While the ground's frozen, we can't pick up many rocks, but every time we get enough of a thaw, she and I look. There's a bit of sidewalk by her school that's completely disintegrated, and we've found some nice rocks there. (I find it a bit ironic that the city demanded that all homeowners in our neighborhood fix damaged sidewalk last year but didn't require that the school do so. That side of the street, along a steep hill, is nasty and treacherous when the weather gets at all bad.)

Comments

[dhaunea.livejournal.com]

We have a tumbler and a grinder here. My grandmother used to do a lot of such things. Want me to hit her up for any thoughts?

[the_rck]

Sure! I'd be grateful for advice.

[adrian-turtle.livejournal.com]

Don't you have plenty of grit in the tumbler now?

[the_rck]

Not really. I've got one package of #3 and two of #4 left but not enough rocks ready for either stage. The tumbler instructions say not to go under 8 oz. when running it, and I've got 5-6 oz. ready for #4 and 2-3 oz. ready for #3.

The tumbler came with two packages of each level, but I've found that no matter how much time I have the tumbler run, it's too short a time for some rocks and is often too long for others. I need to experiment a lot and learn to tell the relative hardness of rocks we've picked up off the ground so that I can group them that way and expect them all to reach the same level at the same time. It doesn't help that I've not figured out any way to check the status of all of the rocks in the tumbler without dumping everything out and needing new grit even if I want to keep on at the same level.

[cherydactyl.livejournal.com]

I think she meant from the sedimentary rocks, or what is left of them. ;)

[the_rck]

Ah. That hadn't occurred to me. Sadly, that stuff went out with the water from those batches. It's also not particularly even.

[adrian-turtle.livejournal.com]

That was what I was thinking. I was partly teasing, but when rocks are naturally polished by tumbling in a stream bed, it's randomly-sized grit that does it. Of course, results from that are unpredictable.

[evalerie.livejournal.com]

I am curious why dumping out the rocks to check them requires new grit. (I don't know the first thing about rock tumbling.)

[the_rck]

Basically, one puts the rocks, the grit and a good bit of water into the tumbler. The grit and water create a thin sludge. The opening of the tumbler isn't very large, so sticking a hand in to fish things out won't work. I can get a finger about halfway to the bottom of the tumbler (which makes cleaning it not fun).

The only way I've found to get all of the rocks out is by dumping the contents of the tumbler into a sieve and then filling the tumbler with water several times, dumping it into the sieve each time. The grit sticks to everything-- the tumbler, the rocks, the bowl I use to catch the water (heeding the dire warnings that the grit will solidify and block pipes if dumped into plumbing), my fingers-- and has to be rinsed off the rocks before they can be inspected.

[evalerie.livejournal.com]

That makes sense.

[evalerie.livejournal.com]

I am nooooooooooo expert on rock tumbling (I've never tried it), but I'm pretty sure that I've seen lovely tumbled rocks that have strata in them, so those would be sedementary. So I think probably it would be only *some* sedementary rocks that disintegrate in the tumbler, not all of them. But I am just guessing -- I really don't know what I am talking about here.

[the_rck]

My guess, based on my vague memories of learning about geology, is that those might well be metamorphic rocks created from heavily compressed sedimentary rocks, but I might well be wrong.

My main trouble with sedimentary rocks is that they tend to have bits that vary wildly in hardness. I can't remember all the types of sedimentary rocks, but I'm sure that conglomerates and sandstone don't work. I suspect that some others would only work if treated very, very carefully and tumbled only with rocks that were like them in hardness.