The Complete Guide to Picking Rocks for Tumbling

Anyone who has ever tried tumbling rocks knows that it can be a difficult task to find the right rocks for your project. The guide below will show you how to pick out the perfect stones from all of those piles at your local stone yard or rock store. We’ll cover what types of stones to look for, how much should cost, and any other considerations you should make before making a purchase.

Characteristics of Good Tumbling Rocks

Most rocks you find in nature are not good for rock tumbling. They are either too dull on the outside, such as shale or mudstone; they will degrade in a rock tumbler, or their sharp edges and points make them dangerous to tumble.

Don’t worry if you can’t find rocks in these exact specifications. Almost any rock can be polished using the tumbling process and most types of stones work well for tumbling. Just keep in mind that different stones will require varying degrees of polishing and work best with certain types of rocks.

Hardness

Soft rocks can be very difficult to polish and usually do not produce the desired results. You should always try to pick out rocks that are at least somewhat hard, like granite or quartzite, when you’re looking for good tumble stones.

The Mohs scale is a way of measuring how easily different minerals scratch other materials and one another. Those with a Mohs Hardness between about six and eight work best for tumbling while softer minerals, like talc or gypsum, can be difficult to polish.

You should avoid rocks that have been weathered too much because they often lose their sharp edges and points from years outside.

Density

Pore spaces trap particles of grit that hit the rocks, ruining the polishing process. Rocks with big pores or low density are not recommended for tumbling because they produce poor results and waste time and money on stones that you cannot use. A good rule of thumb is to pick out dense rocks with smaller pore spaces; these will polish quickly in a rock tumbler without a lot of work.

Fractures

Rocks with fractures will spoil the polishing process by trapping grit in the cracks and breaking parts of your stones into tiny pieces. That is why you should always try to avoid rocks that have a lot of fractures or are covered with seams filled with dirt; these will produce poor results when they come out of your rock tumbler.

It is okay to pick out rocks with minor cracks or fissures because they can be repaired after tumbling using epoxy glue and a bit of patience.

Texture

Rocks that produce granular debris when rubbed together will not polish well in a rock tumbler. You should always try to pick out rocks with smooth surfaces and avoid those that produce a lot of dust or granules when they are rubbed together.

For your stones to polish efficiently, you’ll need as many sharp edges as possible. Rocks without ridges or jagged points will make it difficult to shape your stones.

Color

Just make sure you pick out rocks that are colorful and vibrant because this will help your finished stone stand out from the rest in a display case or on a shelf.

If you want to create an interesting visual effect with two different colors of stones, check for rocks that have similar patterns or coloration at opposite ends of the rock. This way, when you put them in your tumbler together they will produce a neat color-swirling effect as they tumble around each other.

Your stones don’t need to be uniform colors throughout but should have some contrast between different parts of the stone that creates an interesting visual appearance.

Cleanliness

Always try to pick out rocks that are as clean and dry as possible because any bits of moisture, oil, grease, or other substances will contaminate the polishing grit in your rock tumbler. This can also transfer chemicals from one stone to another during the tumbling process.

Size

Size is not as important as shape and hardness but you should still try to pick out rocks that are about an inch thick because those will tumble the best. Your stones should also be about an inch wide to fit into your rock tumbler barrel easily; if they are too small, it can be difficult or frustrating when you try to load them into the machine. If stones are too big, they won’t fit into the barrel at all.

Best Rocks for Tumbling

• Granite: a hard and dense rock that is good for polishing and comes in many different colors
• Quartz: another hard, durable stone with plenty of color options
• Jasper: has beautiful patterns on its surface when polished
• Feldspar/Quartz Family Rocks are the most popular rocks to tumble because they are known for producing wonderful results.

Other popular types of rocks for tumbling include tourmaline, obsidian, citrine, amethyst, and petrified wood.

FAQs

When should I tumble my stones?

You will want to start tumbling them as soon as possible after you pick them out of the ground or river. Rocks with high moisture content can contaminate your polishing grit and damage your tumbler barrel; this is why it's important to find rocks that are dry whenever possible.

How long should I tumble my stones?

If you are using commercially manufactured grit, it's recommended to run your rocks in the tumbler for at least one week to get good results. This can vary depending on what kind of stone you are working with and how muddy or dirty they were when you first picked them out.

How many times should I run my stones in the tumbler?

It depends on how badly your stones are contaminated with dirt or mud; you will want to run them through at least three cycles of polishing grit before they come out clean enough for use. If your rocks have particularly high moisture content, you may need to run them through five cycles before you are satisfied with the results.

Can I leave my rocks in a rock tumbler forever?

If you want to keep your rocks looking their best, it's recommended not to leave them in a rock tumbler more than two months at a time. The very hard quartz and feldspar family of rocks can be left in longer but will still benefit from a break now and then.

Final thoughts

Picking out the right tumbling rock can be a difficult task. You need to consider things like color, shape, texture, and hardness when picking them out for your project. The guide below will help you pick out the perfect stones from all of those piles at your local stone yard or rock store so you don’t have to worry about it anymore! After reading this article on the characteristics of good tumbling rocks, now is the time to find that perfect piece for your next project. Which one are you going to choose?

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