Polishing Unakite in a rock tumbler
Polishing Unakite in a rock tumbler
Unakite stands out immediately thanks to its combination of olive green and salmon pink. The rock usually consists of green epidote, pink feldspar and light quartz-like components. For the rock tumbler, unakite is an interesting choice, but the different minerals do not wear away at exactly the same rate everywhere.
Unakite stands out immediately thanks to its combination of olive green and salmon pink. The rock usually consists of green epidote, pink feldspar and light quartz-like components. For the rock tumbler, unakite is an interesting choice, but the different minerals do not wear away at exactly the same rate everywhere.
What is Unakite?
Unakite is not a single mineral but a rock. The pink parts consist mainly of potassium feldspar, the green parts of epidote, and the light parts often of quartz. It is precisely this mix that gives it its characteristic speckled and marbled appearance.
Hardness
The hardness is around roughly 6 to 7, depending on the component. That says a lot about which stones you can safely combine.
Suitable for the rock tumbler?
Unakite is generally good to tumble, especially if the pieces are compact. Because different minerals come together in one stone, the surface can wear unevenly in places. Very coarse or grainy pieces may polish less smoothly.
Can Unakite go in a rock tumbler?
Unakite is generally good to tumble, especially if the pieces are compact. Because different minerals come together in one stone, the surface can wear unevenly in places. Very coarse or grainy pieces may polish less smoothly.
A separate batch is ideal if you have a lot of unakite. Mixing it with other medium-hard to hard, compact stones can also work, but keep in mind the differences between feldspar, epidote and quartz.
- Use different stone sizes or ceramic media.
- Do not take weak, grainy pieces through to the finest stages.
- Check the transitions between pink and green minerals for small pits.
- Clean very thoroughly between each grit stage.
- Expect a nice shine, but not always a fully glass-like finish.
Polishing Unakite: step by step
Never work by time alone; check the surface after each stage. A stone that still has sharp edges, deep pits or obvious scratches is usually not ready for the next grit yet. You can also find the general process in our step-by-step guide to polishing stones.
Choose compact pieces
Avoid unakite that falls apart grainily or contains many open cracks.
Let stage 1 shape the stone
Remove sharp corners, rough skin and weak protruding parts.
Check for uneven wear
Green and pink zones may react slightly differently. Only move on once the surface is sufficiently even.
Polish with clean media
A clean, well-filled barrel helps the different mineral parts finish more evenly.
Important: clean the barrel, lid, rim, stones and media completely before moving to a finer grit stage. A few remaining coarse grains can cause new scratches in a later stage.
Which grit should you use?
For many tumbler stones, a progression from coarse silicon carbide to ever finer grits works well, followed by a pre-polish and polish stage. The time needed depends on the stone, the starting shape and how much material you want to remove. See the current selection of grit and polishing media.
Coarse grit shapes the stone
The first stage is meant for rounding sharp edges, removing weathered outer layers and grinding away small irregularities.
Fine grit prepares for shine
The final grinding stages remove the scratches from the previous grit. Polishing compound only works properly once the surface is already completely smooth.
Which stones can you combine it with?
A separate batch is ideal if you have a lot of unakite. Mixing it with other medium-hard to hard, compact stones can also work, but keep in mind the differences between feldspar, epidote and quartz.
Hardness is not the only criterion. Brittleness, cleavage, porosity and existing fractures are at least as important. Two stones can be about equally hard and still behave very differently in the same barrel. If in doubt, a separate batch is safer.
Common problems
| Problem | Likely cause and solution |
|---|---|
| Pink and green parts wear unevenly | That is due to differences between the minerals in the rock. Extra time in a fine grinding stage may help. |
| Small pits on the surface | Grainy or weaker mineral parts may wear down a little faster. |
| The shine is not even everywhere | That is not unusual in composite rocks. Good selection beforehand makes a big difference. |
How do you recognise good starting material?
The quality of the rough stone determines a large part of the final result. Prefer compact pieces without deep open cracks, loose crust or very grainy zones. Porous stones can hold grit, and crumbly pieces can produce sharp fragments that scratch other stones.
Suitable
Solid, compact, no loose crust, no deep open fractures and a size that fits well in the barrel.
Less suitable
Very thin protrusions, porous zones, soft weathered skin and cracks that are almost open already.
Polish stones yourself?
With a good rock tumbler, sufficient fill and the right grit, you have the most control over the result. Especially in the coarse stage, take enough time: what is not solved there will usually still be visible later.
Frequently asked questions about Unakite
Is unakite a mineral?
No, unakite is a rock made up of several minerals.
Can unakite go in a rock tumbler?
Yes. Compact pieces are generally well suited.
Why is unakite pink and green?
The pink colour comes mainly from feldspar and the green colour from epidote.
Can unakite be tumbled with jasper?
Yes, but a separate batch gives you more control over the uneven wear of the different mineral parts.