National Geographic Rock Tumbler Review and Results

I got my son the National Geographic Rock Tumbler for Christmas, and full disclosure- it was because I always wanted one as a kid! Read on for my review of the tumbler, how it works, a few tips for the best results and our rock tumbling results after several rounds of tumbling.

Disclosure: I purchased these items on Amazon, and my links are affiliate links.

How to Use the National Geographic Rock Tumbler

I got the National Geographic Rock Tumbler Kit – Hobby Edition ($60) that comes with everything you need to get started: the tumbler, all 4 stages of polishing grit, rough stones, and even a small assortment of jewelry settings to make jewelry with your finished stones. Click here to see the tumbler on Amazon.

The tumbler was very easy to set up and get started. We filled it with some of the National Geographic rocks and some from our stash from years of gem mining in North Carolina.

Next you pour in the Stage 1 grit, fill it with water that just covers the rocks, and start the tumbling. The tumbler has a feature where you choose the number of days you want it to tumble, and it will count down and automatically stop.

And then comes the tough part- waiting for the reveal! Each stage typically takes a week of tumbling, sometimes more.

Tumbler tip: Find a safe place outside to set it up. Even though the listing says it is 75% quieter than other plastic tumblers, it is LOUD. We have it in the garage, and I can still hear it inside the house when it is quiet.

How Rock Tumbling Works:

1. Loading the Barrel – Rough rocks are placed inside a rubber or plastic barrel along with grit (abrasive material) and water. The barrel is then sealed tightly.
2. Tumbling and Grinding – The tumbler slowly rotates the barrel, causing the rocks to tumble over each other. The added grit, usually made of silicon carbide, grinds away rough edges and imperfections over time. This step takes about a week.
3. Progressive Smoothing – The process is repeated with progressively finer grits in separate tumbling stages. The rocks become smoother and rounder with each stage.
4. Polishing – In the final stage, a polishing compound (often aluminum oxide or cerium oxide) replaces the grit. This gives the stones a glossy, polished finish.

Results from Round One of Rock Tumbling

Overall, the results from the first round are the most impressive. You’ll see what was once dull rock, come out of the rock tumbler looking like pretty gems. They will still be rough looking, but you can see their colors coming out. They look shiny when wet but get dull when dry. (The first photo with the tumbler is what the stones looked like going in.)

Stage one is what shapes them, so you want to leave them in long enough to wear away the sharp edges and get them into the shape you want to polish.

Also, make sure you wash your rocks off outside. The tumbler will be filled with a foamy cement-like goo when you open it. Do not put that down your sink or it will clog it up!

This is a video from our latest tumbling batch:

Stages 2 and 3 of Rock Tumbling

The next two stages progressively polish the stones even more. You can see there’s not a huge difference between steps 2 and 3, except they are getting smaller and the edges are smoother.

The Last Step for Shiny Stones

After reading a lot of National Geographic Rock Tumbler reviews, I noticed many mention that the Step 4 polishing powder did not get their stones shiny. I didn’t want to waste a week trying, and I planned to tumble another batch, so I invested in the Polly Plastics Rock Tumbler Grit and Polish Refill, which also comes with reusable ceramic tumbler filler media. Click here to find it on Amazon

Adding ceramic tumbler filler media improves the efficiency of rock tumbling by ensuring a smoother, more even process. One of their primary functions is to cushion and protect delicate stones, preventing chipping and cracking, especially in rotary tumblers.

They also help maintain consistent tumbling action by filling empty spaces in the barrel, ensuring that all rocks receive an even grind and a uniform polishing process.

The filler media is also supposed to help reduce noise, but I didn’t notice much difference.

Two Weeks on Step 4

After week one, the stones looked amazing wet but were dull and hazy when dry. So, we put them in for another week and finally got to see them shine!

You can see some cracks and chunks in some of the stones, because I didn’t tumble them long enough on each step (only 5 days), and kind of rushed through it because we were impatient to see the final result.

They would be smoother if we tumbled longer.

A tip for the finished stones is to rub a tiny bit of oil into them to bring out the shine.

Still Tumbling

After round one was done, we put in a new batch and started the process all over again! We used the rough gemstones again, but next time my son wants to try it with regular rocks and see how they turn out.

Summing Up the National Geographic Rock Tumbler Review

Overall, I would definitely recommend the National Geographic Rock Tumbler, particularly the hobby kit edition. You can use the polishing grit it comes with, but I did not try their stage 4, so I can’t say whether it will shine your rocks. Stages 1-3 worked very well though. Click here for info on purchasing the rock tumbler.

If you do use their polish, I would suggest leaving it on for two weeks, because if it isn’t shiny after week 1, you won’t have extra to go another week.

If you plan to keep tumbling, I recommend getting the Polly Plastics Tumbler Grit & Refill set. It comes with enough tumbler grit to keep you going for several tumbling sessions, and the ceramic filler media is reusable.

And you’ll be surprised by how much the little tumbler can hold! I thought we had enough rocks for several rounds, but I’m almost through all of them just on the second batch.

Also, if you are getting this for a child, be prepared to do most of the work. My son is only excited about it when we open the tumbler after a week, and he gets to see the stones. He also likes to set the tumbler timer.

Rock tumbling is pretty neat, and easy to do. The waiting is the hardest part of the whole experience!