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Rotary Rock Tumblers: How They Work & Which One Is Best?

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Rotary rock tumblers – the ones with a drum that turns – are the most common type of tumbler used by lapidary hobbyists. They can turn rough rocks into beautifully rounded, polished gemstones. They do this by simulating a natural geological process in rivers and streambeds – erosion. 

Rotary rock tumblers are filled with raw stones, water, and grit. As the barrel turns, the stones and grit rub and grind against each other. The abrasion and tumbling action wear down any sharp, pointy parts of the stones, and the surfaces of the stones are smoothed. 

Engaging in the use of a rotary rock tumbler is quite enjoyable. Going into the geology field, you acquire a deeper understanding and knowledge of the subject, leading to the discovery of beautiful gemstones you have personally unearthed. It is essential to get optimal outcomes. This discussion will explore rotary tumbler functions, processes, and optimal options.

What is Rotary Rock Tumbler and How Does it Work?
What is Rotary Rock Tumbler and How Does it Work?

If you are interested in checking out the best rotary rock tumbler, you can find it here (Amazon link).

What Is A Rotary Rock Tumbler?

A rotary rock tumbler is a lapidarist, and gemstone hobbyists use it to smooth and polish rocks and gemstones. Not all rotary rock tumblers are large, commercial-sized machines. Several tiny, high-quality tumblers on the market process 2-to-3-pound loads of rock. 

If you enjoy rockhounding, a rotary rock tumbler is an excellent investment. You can buy a durable one online for between $70 and $150. They are fantastic educational toys for children. 

What Does a Rotary Rock Tumbler Do?

Rotary rock tumblers turn raw, angular chunks of rock into smooth, rounded pebbles. They do this by mimicking the natural process of water erosion, whereby rocks in stream beds are worn down into rounded pebbles and cobbles. 

They are used to process hard rocks, like agate, jasper, amethyst, tiger’s eye, chalcedony, petrified wood, and quartz. Other materials like glass can also be worked in a rotary rock tumbler to make DIY sea glass.

Rockhounds collect rough stones in nature, and when they take them home, they can tumble them into polished specimens. Rough rocks do not always look impressive, but when you tumble, you enhance their inner beauty. 

Natural water erosion takes hundreds, even thousands of years. Rock tumblers speed up this geological process so we do not have to wait millennia to see the magic inside the stones we collect. 

How Does a Rotary Rock Tumbler Work?

Rotary rock tumblers have been designed to reproduce and improve the inherent process of smoothing and refining stones found in rivers and streambeds. However, how do rock tumblers do this task?

Rotary rock tumblers contain a rubber barrel and a motor that rotates it. Certain types have various speed settings and timers, but others are single-speed and solely equipped with an on/off switch.

As the rock tumbler barrel rotates, the rocks within it undergo repeated grinding due to their mutual contact. Small sediment particles detach, particularly from the edges and tips of the rocks. As the duration of running the rock tumbler increases, the stones inside get progressively smoother and more rounded.

Rock tumbling is a rather noisy procedure. To avoid experiencing noise pollution, storing the rock tumbler in your garage, basement, or garden shed while it is in operation is advisable.

After completing the process, you open the rock tumbler and discover your polished stones coated in water and sediment. The colors, patterns, and crystals concealed within the pebbles become visible upon rinsing.

TIP: What rocks can tumble together? Even if you are a beginner or a professional, there is always that curiosity about which rocks can be tumbled together. Find out the answer in the article below:
What‌ ‌Rocks‌ ‌Can‌ ‌Be‌ ‌Tumbled‌ ‌Together:‌ ‌Complete‌ ‌List‌ ‌With‌ ‌Tips‌

How To Use A Rotary Rock Tumbler?

Rotary rock tumblers, especially models designed for hobbyists, are super simple. Besides the rock tumbler, you do require a few other materials and bits of equipment to polish gemstones:

  • Tumbling grit. Coarse, medium, fine, and polishing grit, depending on how shiny you want your specimens to be. Silicon carbide grit enhances the abrasion inside the tumbling barrel, working a bit like sandpaper. Coarse grit helps to wear the rocks’ edges and points down, shaping them. The finer grits help smooth the rocks’ surfaces and polish them. 
  • Tumbling media. Plastic tumbling pellets, ceramic pellets, or walnut shells are added to the rock tumbler barrel along with the rocks, grit, and water. They cushion the rocks as they crash into one another as the barrel rotates, preventing the specimens from chipping, cracking, or breaking. They also help to increase contact between the grit and the stones.  
  • Colander or coarse sieve. You need this to rinse the slurry off the rocks once they have finished tumbling. 

Once you have gathered everything you need to use your rotary tumbler, follow these steps:

Rock Tumbling Phase 1: Shape

  1. Fill the barrel of the rock tumbler two-thirds of the way full of rough stones. Rocks between about 3/8 inches and 1 1/4 inches in diameter work best. The largest rock you add should be no wider than half the diameter of the tumbler barrel. 
  2. Add tumbling media like plastic or ceramic pellets if you do not have enough raw rocks to fill the barrel. It also helps to use pellets if the rocks are flat in shape or are a bit lower down on the Mohs hardness scale. 
  3. Add two tablespoons of coarse tumbling grit for every pound of rock in the barrel. If you use too little grit, the rocks will take extremely long to be shaped. 
  4. Fill the barrel up with water so that the rocks are just covered. Screw the lid tightly shut and wipe away any drops of water on the outside of the rock tumbler barrel. 
  5. Connect the barrel to the rock tumbler, plug the machine in, and switch it on. 
  6. After running it for a week, switch the rock tumbler off, open the barrel, and check if the rocks are the shape you want. Suppose you would like them slightly more rounded; run the machine for another few days. If you are happy with them, use a colander to rinse off the slurry. Do not let it go down the drain! You will ruin your plumbing. Instead, find a better place to dump the wastewater. 
  7. Clean the barrel thoroughly with soap and water before moving on to the next tumbling stage. You want to get every bit of coarse grit out of the barrel so it does not interfere with the next tumbling stage. 

TIP: If you need to cut your rocks to fit the tumbler, you can use many different tools. Check out the best tools for cutting rocks in the article below:
What Can I Use to Cut Rocks? These 5 Tools are the Best!

Rock Tumbling Phase 2: Smooth

  1. Add the cleaned rocks and tumbling pellets back into the empty barrel. 
  2. Add two tablespoons of medium grit for every pound of rock.
  3. Fill the barrel with water as you did in the first tumbling stage and switch the machine back on. 
  4. After running it for another week, switch the tumbler off and open the barrel. You should see that any scratches, cracks, or pits on the rocks have been smoothed. Rinse them off thoroughly using the colander. 
  5. Clean your whole set-up again, getting rid of all the grit.

Tumbling Phase 3: Pre-polish

  1. Next, fill the barrel with the rocks, tumbling pellets, and two tablespoons of fine grit per pound of rock. Add enough water to cover the stones. 
  2. Let the rock tumbler run for another week.
  3. At the end of this phase, the stones should be silky smooth and develop a bit of luster. 
  4. Clean off the stones and the whole set-up again, as before. 

Tumbling Phase 4: Polish

  1. Add the clean rocks, plastic tumbling pellets, and two tablespoons of aluminum oxide powder per pound of rock to the barrel.
  2. Fill the barrel up with water. Let the machine run for yet another week. 
  3. After this phase, your specimens will be glistening! 

Optional Phase 5: Burnishing

  1. If you want to bring out even more brightness in the rocks, you run the rock tumbler for another day. But instead of using polishing grit, add laundry powder or borax to the barrel. 
  2. Clean the rocks and barrel thoroughly before putting them back into the machine after the polishing phase. 
  3. Use two tablespoons of powder for every pound of rock. Use clean plastic tumbling pellets to prevent the rocks from chipping or cracking. 
  4. Your specimens will shine after letting the rock tumbler run for another 24 hours. 

TIP: Now, you know all the phases of rock tumbling. So, you might be interested in how expensive rock tumbling is. Check out the complete cost breakdown in the article below:
Is Rock Tumbling Expensive? Complete Cost Breakdown

Best Rotary Rock Tumblers

Best Rotary Rock Tumblers
Best Rotary Rock Tumblers

A small, 2 or 3-pound barrel rotary rock tumbler is the perfect type to get as a first-time user. But with the sheer number of various brands and models online, it can be overwhelming to pick one!

Here, we present the two best rotary rock tumblers. They are high quality, great value for money, and are available on Amazon. 

Best Option: National Geographic Platinum Series Rock Tumbler (Amazon link)

National Geographic has made rock tumblers as high-quality educational toys for many years. The Platinum series model (Amazon link) is a tiny professional rock tumbler. The kit contains everything you need – grit, polish, 1 pound of rough gemstones, and even some jewelry settings. 

The barrel has a 2-pound capacity. It is made of thick rubber to absorb the impact of the rocks crashing against each other. The motor has three different speeds and a timer so that you can set the number of hours or days the tumbler runs. 

The Platinum Series rock tumbler has a noise-reducing cover over the barrel. This helps reduce the noise so you can run the machine inside your house. 

The machine is designed to prevent softer rocks from being damaged as they tumble. The rock tumbler has a patented “agitate mode” with a gentler motion. 

If you want to buy a National Geographic rock tumbler, check out the latest prices here (Amazon link).

TIP: Rock tumbling is the perfect hobby for kids ages eight. Are you looking for a rock tumbler for kids? Check out the complete guide in the article below:
Best Rock Tumblers for Kids in 2022: Options For Diff Ages

Alternative Option: Lortone 3A Single Barrel Rock Tumbler

The Lortone 3A rotary rock tumbler (Amazon link) is an excellent entry-level option. It is economical, has a 3-pound barrel capacity, and performs well. It only has a single speed, and there is no timer. 

The barrel is made of thick, high-quality rubber that absorbs impact from the rocks as they tumble. It is loud while running, as there is no noise-reducing cover over the barrel. 

The Lortone 3A tumbler has been designed to work for many years. It is not just another toy rock tumbler you can buy online. This rotating rock tumbler is sturdy and easy to operate. 

One drawback is that you must buy all the necessary materials to tumble rocks separately. This rock tumbler does not come with grit, polish, tumbling media, or rough rocks. 

If you’re looking for a basic rotary tumbler that works well, this is the one for you. If you’re buying a rock tumbler for a child, a kit with everything you need may be better. 

How Long Does It Take To Polish Rocks In Rotary Rock Tumbler?

However, polishing rocks in a rotary tumbler is a time-consuming procedure. Nevertheless, it is important to note that this process’s speed is nearly instant compared to the gradual pace of natural geological processes.

To polish a batch of rocks in a rotary tumbler takes 3 to 6 weeks. It can take more or less time – it depends on the type of rock, its hardness, and to what level of finish you would like it polished. 

When considering purchasing a rock tumbler for a child, it is essential. to prepare them for how long the process takes from the beginning. Encourage them to have realistic expectations so that they avoid disappointment. 

If you are interested in buying a Lortone 3A rock tumbler, check out the latest prices here (Amazon link).

BTW: Do you want to know more about rock and mineral identification? The books listed below are the best ones you can find on the internet (Amazon links):


Rotary rock tumblers are machines that process rough rocks into beautifully sparkling gemstones. They do this by replicating and accelerating the natural process of erosion that happens to pebbles and cobbles in riverbeds.

Rotary rock tumblers are easy to use, even for kids! All you have to do is fill the barrel with rocks, pellets, grit, and water and let it tumble away for weeks and weeks. As the barrel turns, the rocks rub and wear against each other. They become rounded and polished.

TIP: Rock tumblers require some maintenance, as you must oil them regularly to keep them running smoothly. Check out how to oil your rock tumbler in the article below:
Step-By-Step Guide: How To Properly Oil Your Rock Tumbler