Rock tumbling: how to make your own tumbled stones
Rock tumbling is the slow grinding and polishing of rough stones in a rotating rock tumbler. As the stones, water and different types of grit move around, sharp edges and scratches are removed. After several stages, you are left with smooth, rounded and often beautifully shiny tumbled stones.
You may also see the terms stone polishing, rock tumbling and stone rolling. They usually refer to the same basic process. On this page, you can read what happens during tumbling, which stones are suitable and what you need to get started yourself.
What are tumbled stones?
Tumbled stones are pieces of natural stone or mineral that have been made smooth and rounded through prolonged movement in a tumbler. They are also called tumbled stones, polished stones or pocket stones. Well-known examples include tumbled stones made from agate, jasper, carnelian, tiger’s eye, rose quartz and amethyst.
The term tumbled stone can also be used online for tumbled paving stones and setts. On Rocktumbler.nl we use it to mean the smaller polished gemstones, minerals and other suitable natural stones that have been processed in a rock tumbler.
Still has its natural shape, sharp edges, pits and a dull or weathered surface. As a result, colours and patterns can be less noticeable.
Has been gradually rounded and smoothed in a rotating tumbler. The stone keeps a free, organic shape and is not ground into one fixed form.
Is deliberately ground into a specific shape, for example with flat facets for jewellery. That is a different technique from rock tumbling.
How does rock tumbling work?
In a rotating rock tumbler, a rubber or plastic barrel slowly turns round. The stones constantly fall and roll over one another. Grit in the water forms an abrasive mass, also called slurry. This reaches the surfaces between the stones and gradually grinds them smooth.
You work from coarse to fine. Each new stage removes the scratches from the previous stage. The final step does not use coarse grinding grit, but fine polishing powder to build the final shine. The process below is an overview. For quantities, check points and cleaning, go to the detailed step-by-step guide to stone polishing .
Coarse grinding
Coarse grit rounds off sharp edges, removes protruding parts and largely determines the final shape of the tumbled stone.
Further refining
Medium-coarse and then finer grit reduce the scratches from the first stage. The stones feel smoother and smoother.
Pre-polishing
Very fine grit or pre-polish prepares the surface for the final polish. Any deep scratches left behind are especially important now.
Polishing
Polishing powder brings out the shine. This only works well when the stones have already become sufficiently smooth in the earlier stages.
Which stones can you tumble?
For a first batch, hard, compact stones are usually the easiest. Agate, jasper, carnelian, tiger’s eye and many quartz-like stones can become beautifully smooth and shiny. Choose pieces without deep cracks, open cavities or crumbly edges.
Stones in the same batch should preferably be about equally hard. A hard stone can continue to scratch a much softer stone during tumbling. Fragile minerals, crystal clusters, porous stones and heavily cracked pieces therefore require a different approach or are not suitable at all for a standard beginner batch.
How long does rock tumbling take?
A full batch usually takes several weeks. Many people allow about one week per stage, but that is not a hard rule. In particular, the first coarse stage can take longer when stones still have sharp edges, pits or an irregular shape. Sometimes that stage needs to be repeated before it makes sense to move on to finer grit.
Moving on quickly does not automatically produce beautiful tumbled stones any sooner. Scratches and pits that you leave in the coarse stage usually will not disappear in the finer stages. Check the result after each stage and let the condition of the stones determine when you continue.
A rock tumbler usually runs day and night. So take the rolling noise into account and place the machine stably in a location where it can run safely and will not cause a disturbance.
What do you need to make tumbled stones yourself?
The basics are straightforward, but the parts still need to match each other. Having just a barrel and a bag of random stones is not enough.
A rotating rock tumbler
For the classic rounded tumbled stone, you usually use a rotating rock tumbler. When choosing one, pay attention to capacity, noise level, barrel quality and the availability of spare parts.
Rough stones and filler
Use suitable stones in different sizes. The barrel needs to be filled enough to prevent hard impacts. Sometimes ceramic media or plastic pellets help achieve the right fill level and movement.
Grit and polishing powder
You need several grit sizes and a proper final polish. Use clean material for each stage and always follow the step-by-step guide and the instructions for your machine and grit when dosing.
Common mistakes in rock tumbling
A disappointing batch is not always due to the machine or the polish. Often something went wrong in an earlier stage. These mistakes cause many dull stones, scratches and chipped edges.
Moving to the next stage too quickly
Fine grit cannot make up for deep pits and coarse scratches afterwards. So let the first stage run long enough and assess each stone critically.
Not cleaning thoroughly enough
A few coarse grit grains from an earlier stage can cause new scratches in the polishing stage. Clean the barrel, the lid and the stones very carefully.
Incorrect barrel fill
With too little fill, stones can fall hard and get damaged. With an incorrect fill, the mass may move poorly and hardly grind at all.
Combining the wrong stones
Soft and hard stones do not wear evenly. Brittle pieces can also break apart and contaminate or damage the rest of the batch.
Rinsing slurry down the drain
The used abrasive mass can settle and clog pipes. So do not pour slurry into the sink or toilet, but let it dry and dispose of it appropriately.
Using only fine grit
Fine grit does not automatically make a rough surface mirror-smooth. Each stage has its own job, and true shine ultimately requires suitable polishing powder.
Rock tumbling with children
Making tumbled stones is also fun to do with children. Searching for and sorting stones, photographing the different stages and comparing the final result make the process tangible and educational. Because the result is not ready immediately, children also experience how a slow process changes step by step.
Let an adult operate the machine, measure out the grit, open the barrel and clean up the slurry. A rock tumbler is an electrical appliance and the grinding powder must not get into the mouth, eyes or drain. Read more about this hobby for families on the page stone polishing as a new hobby for young and old .
What can you do with tumbled stones?
Many tumbled stones are beautiful enough on their own to keep. However, you can also use them in a creative project, as long as the application suits the size, hardness and shape of the stone.
Collecting
Store stones by type, location or batch and note what you used during tumbling.
Decorating
Use them in a bowl, glass jar, plant corner or other decorative display.
Giving as a gift
A stone you found yourself and polished is a personal small gift with a visible story.
Creative use
Suitable stones can be used for wire wrapping, pendants, mosaics or other hobby projects.
Frequently asked questions about rock tumbling
What is the difference between rock tumbling and stone polishing?
The terms are often used for the same process. Rock tumbling mainly describes the movement in the rotating barrel. Stone polishing puts more emphasis on the smooth, shiny end result. A full tumbler batch includes both grinding and polishing stages.
What are tumbled stones?
Tumbled stones are pieces of natural stone or mineral that have been gradually rounded, smoothed and usually polished in a rotating barrel. They keep a free form and are not cut into fixed facets like a gemstone.
How long do stones need to stay in a tumbler?
A full batch usually takes several weeks and consists of multiple stages. Many stages take about a week, but coarse grinding in particular may take longer or need several rounds. The condition of the stones determines when you can continue.
Which stones are suitable for tumbling?
For beginners, hard, compact stones such as agate, jasper, carnelian, tiger’s eye and many quartz-like stones are often suitable. Avoid heavily cracked, porous, brittle or very soft stones, and preferably combine stones with a similar hardness.
Can you tumble stones from nature?
Yes, some found stones are suitable. Check hardness, compactness and fractures, wash the stones well and only take them where collecting is allowed. Not every beach, river or field stone will become beautifully shiny.
Why are my tumbled stones not shiny?
Common causes are unsuitable or mixed stone types, moving on too quickly, leftover coarse grit, incorrect barrel fill or unsuitable polishing powder. First check whether the stones were fully smooth before polishing.
Can you pour slurry down the sink?
No. The abrasive mass can settle, harden and clog pipes. Collect the slurry, let it dry where possible and dispose of it appropriately without pouring it down the sink or toilet.
Make your own tumbled stones?
Start with a suitable rock tumbler, a simple mix of hard rough stones and a complete grit set. Then read the full step-by-step guide before filling your first batch. That way you know in advance what each stage does and avoid the most common beginner mistakes.