Sunday, January 26, 2014

Rock Tumbling for Beginners

Mixed rocks, before and after tumbling
We got a rock tumbler at the end of last summer, in preparation for our rock unit. I always wanted a tumbler when I was little, but my mom told me that they didn't work very well---and Sam, who DID have one as a child, confirmed this. He said his tumbler never did a "dang thing" (I believe I am quoting him exactly) to his rocks. :)

So, I was wary of buying one that didn't work. I read a lot of reviews and finally settled on this one that has two barrels (so we could do more than one kind of rock at a time). I also bought some rough rock to tumble (at that time we hadn't collected any rocks of our own), some grit, and some tumbling beads (to cushion the rocks as they tumble). We really like our tumbler; it's sturdy and it runs really quietly in our laundry room. We oil it every couple weeks with a lightweight oil (something like this) and so far, it's had no problems!

It has been super fun to learn more about polishing rocks. We've realized more and more that there's quite an art to it---selecting the right stones, and dealing with variations in the timing of the tumbling, and getting everything clean, and so forth. We're still really new at it. We talked to a guy who owns a rock shop in Salt Lake, and he was really helpful. One of the best things he told us was that we could use rubber bands instead of the plastic beads for cushioning. You can get bags of rubber bands at the dollar store or Hobby Lobby and they're lots cheaper than the beads! And we've found better places to get the different types of grit, also (that shop in SLC sometimes has good sales, and we don't have to pay shipping, and this place online is pretty good too).

Like I said, we are not experts at this process yet, but if you've never tumbled rocks before, you might not know (as I didn't) that it takes quite a long time in a rotary tumbler. You do the rocks in four different sizes of grit (moving from rough to fine) and it takes about a week (or more) for each stage. (Learn lots more here, if you're interested.) So you don't get to see the final results until about a month after you start, but I think that adds to the anticipation and excitement of it. We love checking on our rocks every week and seeing how they are coming along! 

The first rocks we tumbled were those mixed rocks that I got online (pictured at the top of this post) and they were quite fun. I'm not sure we did them long enough on the first stage, because some of them still had little chips and pits in them, and not all of them acquired a really nice shine by the end. But they are still pretty and we were all delighted with them!

Once we starting going out to collect our OWN rocks, though, that's when things got really fun. I'm not sure I can adequately convey how exciting it is find a rock outside, take it home, lovingly take it through the tumbling process, and then have it emerge as a beautiful, smooth, gleaming work of art. We feel almost paternal toward our little rock children. :) And it's so surprising, every time, to see the shapes and designs and patterns that emerge as the rocks become more polished. You can't ever predict what your finished rocks will look like, which is part of the fun of it all!
Wonderstone, before and after tumbling
Here is our tumbled wonderstone, which we collected here. I think this is my favorite---or maybe my second-favorite---of our tumbled rocks so far. It's hard to choose. :) The change is SO dramatic once they're polished, because all the bands and colors become more prominent. I just love seeing how they turn out! We have done a couple different batches of this now.

Wonderstone is kind of porous, so it doesn't "take a polish" (meaning, it doesn't really get shiny) very well. But the smoothing of the rocks in itself is worth doing, because it sharpens the colors and bands so well. When ours came out of the tumbler (last stage---we tried the polish anyway, just in case) they looked like this:
I made a kind of odd discovery, though. This is not an "official" thing to do to polished rocks---maybe it ruins them; I don't know; can you ruin rocks??---but always after cleaning out the tumbler barrel, my hands are dry from all the washing and scrubbing, so I always put lotion on my hands. And one time after doing this, I was holding and feeling one of the rocks, and some lotion got on it, so I rubbed it in, and it deepened the colors and made the rock look smoother and shinier. We liked how it looked and felt after that, so we rubbed lotion into some others, and they looked really pretty. It makes sense, I suppose, because of the effect of the oil on the outer layers of rock. Maybe you could just rub regular oil, like olive oil, into the rocks and it would look nice too. I might experiment with that next time. Of course this would be unnecessary with rocks that do get shiny and truly polished, but with the wonderstone, we liked the results. Remember that we don't really know what we're doing, though, so take that into account if you try this! :)
Wonderstone (with lotion rubbed in)
Calcite, before and after tumbling
Here is our tumbled calcite, collected here. Calcite is a really soft stone, and some sources said it wasn't good for tumbling at all, but we just wanted to try it anyway. It is really beautiful (and you can see the crystal shapes) without being tumbled, so it's certainly not necessary to tumble it. As you can see, lots and lots of it just gets ground away, so it really reduces in size. And we didn't tumble it as long on each step (I think we did 3-4 days instead of a week). And, because it's so "dusty" (?) and soft, it doesn't get very shiny either. But some of the pieces are translucent, so they almost look shiny because of that. One of the pieces I liked best had almost-transparent bands through it. It's what I think of when I hear "alabaster," and in fact I learned that alabaster IS another word for calcite. Lovely. We like having some of each kind of calcite, tumbled and non-tumbled. Both are beautiful in their own ways.
Obsidian, before and after tumbling
These rocks are obsidian, or apache tears, which we collected here. We read that obsidian is "difficult" to tumble. I guess it breaks really easily (because it's glass, of course) and then the broken shards will scrape the rest of your rocks. You can read more about tumbling obsidian here. I think we must have done something wrong, because ours ended up less shiny than they were at first. We used corn syrup instead of water to tumble them in (the more viscous liquid helps prevent breakage) and we used the cerium oxide (rather than the aluminum oxide) polish---but they still ended up with this lovely matte finish. I'm not sure what we did wrong.
However, when we first collected them, they were usually only shiny on one face (as above)---where they had broken most recently, I suppose. The other sides were not "matte," but actually dull. So our tumbled stones were an improvement, in many ways. And what is really remarkable about them is how SOFT they are---seems a strange word for a rock, but it's all I can come up with. The smoothness was so silky! Much "softer" than the glossier-looking green quartz (below). And I really do like the matte finish. But I would like to know how to get them looking glassier, like in this picture.
In the light this almost looks like hematite. It seems totally opaque.
But it's actually slightly translucent, and this piece had bands inside. Really pretty.
You can see the light coming through it from behind.

Green quartz, before and after tumbling
Quartz is a really popular stone to polish, and that's probably because it works so well! We ordered this rough green quartz on eBay. It turned out the most glossy and shiny of all the rocks we tumbled. It has that classic "polished rock" finish. We love it. We wish we knew a place to go collect some quartz! Maybe next summer.
Malachite, before and after tumbling
Now we come to my very favorite! Malachi got some rough malachite for his birthday (it's his favorite mineral, of course) and we weren't sure how it would tumble, but we wanted to try it. The guy I bought it from said it was a 4-5 on the Mohs Scale, so we should tumble it carefully, but it would work. We tried doing it for only 4 days on the first stage of grit, but it wasn't smooth enough after that time, so we kept it going, checking it every few days. It took almost 10 days on the first stage, to get all the cracks out. We ended up tumbling it just as long as the other rocks we tried---about a week on each stage (after the first).

I looooove how the malachite turned out. I just can't stop looking at my piece (Malachi gave each of us one of the pieces to keep; wasn't that nice of him?). It feels so smooth and I love the way the bands of lighter green glow against the deep green around them. I love the waves and ripples. I love how each rock has its own character.

Malachite is expensive, compared to other stones, and I also had a hard time finding any that wasn't already tumbled or cut. Finally I found a great store on eBay that has TONS of awesome rocks and minerals. The owners are really nice too, and if you buy a bunch of stuff they combine it and ship it all to you in a big flat-rate box so it's not too expensive. They were really good about answering my questions and they have such a huge selection! I only got a few pieces of malachite for Malachi's birthday, but now that we're all so into rocks and minerals, I felt like I could have browsed their store forever.
We love tumbling rocks and we're so happy we found this hobby! We never imagined we could have so much fun with it. Come visit us, and we'll give you some of our rocks! :)


  1. These turned out so great! I loved the wonderstone and malachite too!

  2. Ohhh my goodness.... Thank You so much for sharing!! My husband got me a tumbler approx. 6-9 months ago. I have not had the time until now & secretly I believe I've been a little nervous about it all. I've always collected pretty rocks and have always wanted to learn about them. I just don't want to ruin a perfectly nice batch or worse yet, hurt the tumbler... lol I guess its time for me to "Cow Girl Up" & get to it. You have given me the inspiration to get started.... Thank You

    1. Oh, I'm glad this was helpful! Good luck tumbling your rocks! It's so fun to see how they turn out. :)


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