Top Tips for Rock Tumbling

Here are our top tips for rock tumbling. Whether you're a beginner that's just starting out or have been at it a while, we hope there will be something useful here for everyone. 

1. Choose the Right Rocks

Not all stones are suitable for tumbling. Softer rocks such as limestone, shale, or sandstone will often crumble during the process, leaving you with dust rather than polished gems. Instead, look for harder stones with a Mohs hardness of 6 or above. Good choices include:

• Agate
• Jasper
• Quartz
• Amethyst

You’ll also want rough rocks of a similar hardness in each batch, as softer stones will wear down much faster if mixed with harder ones.

2. Shape Matters

When selecting rocks, pay attention to their shapes. Smooth, rounded stones will tumble much more effectively than jagged, angular ones. Sharp edges often chip off during the process, producing scratches that become more time consuming to polish out. 

3. Don’t Overload the Barrel

A common mistake is to cram as many stones into the tumbler barrel as possible. While it may seem efficient, overloading prevents the rocks from moving freely, reducing the quality of the polish. On the other hand, too few stones will cause excessive chipping. Aim to fill the barrel to around two-thirds to three-quarters full, adding ceramic media or plastic pellets if needed to achieve the right level.

4. Be Patient With the Stages

Rock tumbling typically involves at least four stages: coarse grind, medium grind, fine grind, and polish. Each stage can last a week or more, depending on the stones and the rock tumbling grit used. The temptation to rush ahead is strong, but patience is key. If you move to the next stage before all scratches are removed, they’ll remain visible in the final polish. Remember: don’t advance until you’re satisfied with the finish at each stage.

5. Clean Thoroughly Between Stages

Cross-contamination is one of the most frustrating pitfalls in rock tumbling. Even a small amount of coarse grit carried into the next stage can scratch your stones and ruin weeks of effort. After each cycle, wash both the rocks and the barrel meticulously. An old toothbrush can help remove grit from cracks and crevices. Some enthusiasts keep a separate barrel for polishing to eliminate the risk altogether.

6. Mind the Noise

Rock tumblers can be surprisingly noisy, especially during the coarse grind stage. If you’re living in a small flat or have thin walls, you’ll quickly learn why some people give up on the hobby! To minimise disruption, place the tumbler in a shed, garage, or basement if possible. If that’s not an option, try setting it on a thick rubber mat to reduce vibrations.

7. Reuse and Recycle Media

Ceramic media and plastic pellets aren’t just filler—they play an important role in cushioning the rocks and ensuring an even polish. They can also be reused for multiple cycles, provided you keep them separate for each grit size to avoid contamination. Clearly labelled containers will save you from costly mistakes.

8. Keep Records

It may sound overly organised, but keeping a simple notebook of your batches can be invaluable. Note down the types of stones used, grit sizes, duration of each stage, and any observations. Over time, you’ll develop a better sense of what works best for different materials, making future batches even more successful.

9. Expect Imperfections

Even with the best care, not every stone will emerge flawless. Some may have hidden cracks, flaws, or inclusions that prevent them from taking a perfect polish. This is part of the charm of rock tumbling: nature’s unpredictability. Embrace the variety—you’ll still end up with a collection of unique, beautiful stones.

10. Enjoy the Journey

Rock tumbling isn’t a quick hobby. From start to finish, a batch can take four to six weeks, sometimes longer. But that’s part of the appeal. The slow transformation from dull, rough stone to gleaming gem is deeply satisfying, especially when you’ve put in the effort yourself.

Final Thoughts

Rock tumbling is more than just a craft—it’s a way to connect with the natural world and uncover the hidden beauty within ordinary stones. With patience, care, and a bit of experimentation, you’ll soon find yourself hooked on the process. Whether you’re making jewellery, decorating your home, or simply admiring your polished stones, the results are well worth the wait.