how to polish rocks

How To Polish Rocks In A Rock Tumbler – Do This First

The How To Polish Rocks Series

This is Part 1 In Our 5 Part "How To Polish Rocks Instructional Series". Be Sure To Check Out -

The First Steps Before The Actual Grinding

Over the years, I have learned simple and easy, but very important, tips, tricks, and details that come in handy when learning how to polish rocks in a rock tumbler. Today, we’re going to go over the preliminary steps and find out a few important things to look for that can make or break your final batch of polished stones.

​There are 4 things you will be doing when polishing rocks in a rock tumbler -

  1. Rough Grinding
  2. Medium Grinding
  3. Fine Grinding
  4. Polishing

Further still, if you want professional looking results, you may even need to split the last step into two polishing stages.

Hardness Of The Stones

Before you jump right into tumbling the stones, you have to get them ready for the process. This involves some steps such as sorting and preparing the rocks. All stones will need to be separated according to their hardness level. Of course, they don't have to be exactly the same hardness, but they need to be in the ballpark of one another. Sometimes, you might even have some extra brittle stones in a batch of the same hardness. These will need to be pulled out and sorted separately. You can then tumble the extra brittle batch without any other stones. That way, you don't lose out on any rocks, but you also don't mess up a whole batch because of some brittle stones. The National Park Service provides an overview image below,  of some common minerals compared to everyday objects on the right.

Mohs Hardness Scale Rock Polishing

One thing to keep in mind, are how the stone types behave in the tumbler. For example, Apache Tears, and Obsidian are both forms of glass from volcanoes, but they react differently in the tumbler and will need to be tumbled at different times. If you're just starting out, don't worry too much about this. This is the kind of knowledge that comes with experience and it's just a little extra nuance that shouldn't stop you from starting your rock tumbling journey.

Types of Rocks To Tumble

If you are a beginner, I recommend starting out with easier rocks to tumble that will provide consistent great results without a lot of expertise. Some of these varieties include agates, flint, and jaspers. The common thing to look for in a beginner stone is a hardness of around 7 or so. These quartz rocks fall into that category. With this level of hardness, any beginner mistakes you might make will be forgiven by these tough stones.

Size Up The Stones

The rocks should be around a half inch or 13 centimeters to one and a half inches at the biggest spot. Anything bigger will need to be broken down with a hammer or chisel (note - be sure to wear eye protection when breaking rocks). One method of breaking rocks is to use a hammer and chisel with a plate made of steel. You put the plate on a padded surface like several pieces of paper for example, in order to soak up some of the hammer's blow. Wearing the appropriate protective gear (i.e. eye protection and gloves) you'll then use the chisel to crack the rock. Not all rocks will have them, but a fracture line on the rock is a good place to start. Inspect the rock for this line and then place the chisel there. Give it a good sharp strike and it should break apart fairly easily.

If the rock only cracks, subsequent lighter strikes can help it along until it comes apart.

While you've donned your own protective gear, also keep those around you in mind. Anyone standing around you should be back away and also in protective gear. Rock fragments can fly a long way and easily cause damage to a person's eye.

Washing The Stones

Once you've cracked the larger stones into smaller more uniform pieces, be sure to wash them thoroughly. In fact, that is a required step for all of your stones, whether you cut them first or not. Use a stiff brush to get out any and all stubborn dirt and rock chips. You want a nice uniform surface as free from contamination as possible. Any impurities will impede the action of the grit you are using and cause the finished product to be inconsistent.

Inspecting the Rocks Prior to Tumbling

While washing your rocks, you can also inspect them for any cracks or issues that will be brought out during the tumbling process. If a rock is cracked, the tumbling action could cause it to break apart in the tumbler and mess up a whole batch. A good strong flashlight is useful for inspection as well.

If you find rocks that are cracked, set them aside for suture manual work. You may be able to break them up and clean them for use in a different batch.

Another thing to check for is excessive pitting or sponge like areas in your rocks. These pits will cause abrasive to get trapped in them and they won't polish well. These will need to be thrown out. Any tiny pieces and chips will need to be discarded as well and only uniform size rocks should remain.

Write Down Your Data

One thing that is helpful to do at the beginning of the tumbling process is to make a log sheet to track all of your data for the batch. This is something a lot of beginners fail to do and wish they had done it after the process is complete. The more batches of rocks you tumble, the more data you will have. After awhile, you will be able to look back over your log sheets and have a lot of knowledge to make each new batch that much more professional looking and consistent. This is how experienced rock tumblers develop their own rock tumbling secret sauce.

You data will come in handy for things like the amount of abrasive that works best in your tumbler, fill level of the tumbler, and polishing quirks for each type of rock in your particular rock tumbler.

The Next Step

Once you have prepped your stones, you'll be ready to start the rough grind and be on your way to your next batch of polished stones! Be sure to check out the next installment in our series on how to polish rocks in a rock tumbler where we’ll go over the rough grind and the secrets to a great foundation grind.

The How To Polish Rocks Series

This was Part 1 In Our 5 Part "How To Polish Rocks Instructional Series". Be Sure To Check Out -

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