What Happens in a Rock Tumbler? (You Will Be Surprised To Know!)

Problem of Rocks Getting Dull After Tumbling

Did you ever come across a very round and well-polished rock by the river? Did you pick it up and realize how beautiful and finely shaped it was? If you’ve had this experience before, you might have wondered how a basic rock turned out looking so nice. 

How Can You Make Well-polished Rocks?

Best Rock Tumbler Buying Guide

Well, there are two ways that rocks end up looking well-polished and perfectly shaped. One is through the forces of nature. When rocks rub against water, other rocks, sand, wood, or gravel, their shape slowly gets changed. Their texture even loses its coarseness if they have been rubbed with sand over a long time. But yes, that takes a long time – years, even decades. What if you want to have these kinds of rocks in a shorter time?

Don’t worry, that’s possible, too. This brings you to the second way of polishing rocks – through the use of rock tumblers. Rock tumblers are not storage spaces for rocks. Rather, they’re devices that mimic how nature polishes and rubs the rocks to produce smooth and jewelry-worthy stones. 

Curious to know more about a rock tumbler? Read on to discover all about it. 

What is a Rock Tumbler?

How Long Does Rock Tumbling Take

A rock tumbler is a simple device that shapes and polishes your rocks so that they can be used for jewelry, crafts, and different artworks. If you’re a rock collector, a rock tumbler can be a good hobby device for you to have. 

A rock tumbler uses the physics of friction to shape and polish the rocks. That’s where the grit, water, and rocks are helpful. By the way, those three are also the only materials you’ll need. Anyway, these materials are placed in the tumbler so that they can turn together and rub against each other for weeks. The finished product is no other than fine-looking stones. 

How Does a Rock Tumbler Work?

Still curious as to how a rock tumbler produces beautiful rocks? Here’s a more detailed explanation of how rock tumblers work. 

Its main material needed, aside from the rocks themselves, is the grit. Grit is like sand, only it comes in different sizes and textures. Think of it as sandpaper rubbing against your rocks. You’re starting to get the picture now, right? If sandpaper is used to polish small pieces of wood, then grit is used to polish rocks in a tumbler. 

There are three types of grit you’ll need – coarse, medium, and fine. They’re the same grades you’ll find on sandpaper, too. When you have those three types of grit, you have to place them one by one after a few weeks. To be specific, during the first two weeks, the coarse grit is placed with the rocks and water to polish the rocks. In the third week, you place the medium-grade grit. And in the fourth week, you place the fine-grade grit. 

Needless to say, the rock tumbler turns and tumbles for weeks on end. Until you’re not satisfied with the texture and shape of your rocks, you can extend the whole process. 

What about the water? Well, the role of the water is to make the tumbling environment a lot like nature. The water acts like the river that smoothens out the sharp edges and improves the overall texture of the rocks. 

4-step Tumbling Process

Size of Tumbler Determines the Size of the Rock

A rock tumbler is very easy to use. But if you’ve noticed a while ago, it undergoes several processes before you get that smooth rock you want to use on a necklace. So what are the processes the rocks go through?

1. Shaping with Coarse Grit

The first step is the longest in the process because it does the initial job of softening the sharp and rough edges of the rocks. Don’t worry, after the long wait of around 2 weeks, you’ll see a significant difference in the shape of the rocks. 

To start with the shaping process, place a lot of rocks in the barrel. Here’s a tip, place different types of rocks with different shapes and sizes so that it gives a different type of friction to the other rocks. When the barrel is two-thirds full, add the coarse grit. For every pound of rock, you should add two tablespoons of grit. Don’t forget to be mindful of the maximum weight your tumbler can carry. 

When both the grit and the rock are there, start the tumbling process. Be ready – it’s going to be noisy. Since these coarse rocks are going to be bumping each other, they’re going to produce a loud sound. It’s best to place them in the garage for the meantime. 

2. Shaping with Medium Grit

Should you wait for two weeks? No, not really because some rocks get shaped after a week. However, some don’t, so it’s really best to check after five days. If you’ve achieved the texture and shape you want, then you can proceed with the next step which using medium and fine grit. If it still needs a lot of tumbling in step 1, then you just have to put it back again and wait for another few days.

The second step is simply using a medium grit. Before you place the new types of grit, remove the rocks from the tumbler and wash the barrel with soap and water. This is the preparation stage so that there’s no coarse grit is left. 

When the barrel is dried out, put back the stones and place the medium and fine grit. Make sure to not go over the maximum weight limit.

3. Pre-polishing

Wait, don’t the past two processes include polishing already? Well, not yet because the first two processes were just meant for shaping the rocks. This pre-polish stage is setting it up to make the rocks look bright. 

So what do you need for the pre-polishing process? All you need here is soap and water. When the rocks have your desired shape and texture, you can remove them from the barrel and wash them with water. Wash the barrel as well and make sure that there isn’t any grit left. 

4. Final Polishing

The final polishing involves fine grit. Place the rocks back, but this time, place plastic pellets, too. Plastic pellets prevent the rocks from hitting each other. Otherwise, you’re going to “scar” the rocks, making it hard for them to shine after the polishing process.

After the plastic pellets, place the fine grit. Turn on the rotary tumbler again and wait for a week. By the end of the week, your rocks should have that shine that you’ll see on bracelets and necklaces.

What is Burnishing?

If you’ve never heard of burnishing, it’s an additional process after you’ve polished your rocks. It’s not really a necessary step because if you’re content with the texture and shine of your rocks, then there’s no need to reach the burnishing stage. However, if you want more shine, it’s best to take this step. 

To check if your rocks will benefit from burnishing, try to buff the rock on one side. If it shines, then you can burnish them. If not, then that’s the shiniest the rock will get. 

To start burnishing, place two tablespoons of powdered laundry detergent for every pound of rock you have. Place plastic pellets in the mix, too, so the rocks won’t hit one another. After that, you just leave the tumbler on for a full 24 hours. 

Types of Rock Tumblers

Where to Run A Rock Tumbler

Is a rotary tumbler the only type there is? No, it isn’t. There’s also another type of rock tumbler which is vibratory. What are the differences between the two?

1. Rotary Tumbler

The most common type of rock tumbler is the rotary. Just like its name, its mechanism rotates to turn the stones together with the grit and the water. It’s a lot like how a wheel moves. 

The rocks, grit, and water are placed inside the container where all of them are turned once you turn on the motor. Because there are different stones, it’s bound to make a lot of noise. However, the noise isn’t that bothersome as you would think. It’s just like a water bottle being shaped.

2. Vibratory Tumbler

The other type is the vibratory rock tumbler. This tumbler uses vibrations to move the stones amongst each other. The vibrations are at high speeds so that there’s enough force for the stones to hit each other. The movement produced between the stones and the grit produces softly rounded edges without altering the stones’ original shapes too much. 

The vibratory tumbler is suitable for people who want to retain the original shape of the stone while making them a little smoother than their original texture. When it comes to the length of time they are vibrated, it’s similar to the rotary tumbler – it also takes a few weeks.


Rock tumbling is the process of shaping and shining rocks that you’ll use in our arts and crafts. Some do it as a hobby. If you’re fond of smooth and shiny rocks, then you can use a tumbler to produce your beautiful stones. What’s great about rock tumbling is you don’t have to wait for nature to create these stones.

Sharing is caring!

Picture of LillianDodd


I manage the Publishing side of things here and specifically responsible for Travel Section as an Editor. Through this section, I intend to provide all the tiny little nuggets that I managed to capture in my experience of travelling to countless countries. I have been featured on Timesticking, Yahoo Finance, Bestlifeonline, Finance at USnews, CreditIgniter and numerous publications. To sum it up: I am a Thinker. Beer evangelist. Certified organizer. Typical tv practitioner. Vegan fanatic. Introvert and an Extreme travel nerd.
0 0 votes
Article Rating
Notify of
Inline Feedbacks
View all comments

Related Posts

Subscribe To Our NewsLetter!

Would love your thoughts, please comment.x