Rock size question

I think 5 inches pushes it, but you might get one in. Especially if it is like a mussel and not like a baseball.

Remember it is the rocks slide across the diameter of the barrel as it falls from near top to near bottom that grinds it. THe biger the rock, the less the slide. Just like shorther strokes across sandpaper, this will take longer.

Remember also that sliding across small high spots of other large stones is not a good slide with lots of surface area. SO any large rocks still need to slaide across a surface that is filled in with many smaller rocks, so that the surface is as complete and effective as possible.

OF course if either of the conditions is less than perfect, it jsut means a little longer. It is when things are far form perfect that the whole process breaks down and stops working.


Also keep in mind it is not just the size of the rocks, but the size of the crevases. Many small rocks might have only 1/8" deep flaws. Larger rocks might well have 1/4 inch deep flaws. It is going to be twice as long before the large rock is done because it has twich as much material to remove.

So you can add SOME larger stones, but retain the full mix of sizes. ALso, you might have to move the smaller stone on sooner to the next stage.

Yes to what Deb193 says. Also, only use one big rock in a barrel at a time. I've tried 3 big pieces of petrified wood (much smaller than what you are talking about), and they beat each other up, even with plastic pellets for cushioning. And any other stone in the barrel that gets sandwiched between two big tumbling stones is going to be in for a rough time.

I use Lortone 6 lb barrels, which are the same diameter as the 12 lb barrels, but half the length. The biggest stone I've tried tumbling was smaller than what you are talking about -- I think it started off at marginally over one pound, and I forget the starting dimensions but the finished dimensions are 3.5" x 2.5" x 1". I used some regular size tumbling stones in with it, plus a fair bit of pea-sized garnets so that the very big stone would be balanced out by some very small stones. It worked out well so I think you could do something larger in your barrel, but note Deb193's comments about what factors will dictate the ultimate limits.

Here's the biggest stone I've tumbled:


And here's a few of the small garnets I used to help balance things out in the barrel:

rollingstone ,that is afantastic rock & the garnets are nice too ! paul