Rock Tumbling Guide Part 1: Buying a Rock Tumbler

Anyone who has ever visited a rock shop has seen the beautiful, polished semi-precious gems which are typically offered for sale. These stones are very smooth, almost glassy in their texture, and the smoothness helps to bring out their underlying patterns or hues.

Have you ever wondered how gemstones which start out as the rough rocks you find outdoors turn into these shiny, colorful polished stones? You can actually achieve this entire effect yourself at home with the aid of a rock tumbler.

The majority of gemstone hobbyists use one of two different types of rock tumblers. These are called rotary rock tumblers and vibratory rock tumblers. Rock tumblers are also available for children. These tumblers are cheap, wear out quickly, and operate loudly. They are less expensive though, and may offer you a starting point to decide if rock tumbling is for you and whether you should invest in a rotary tumbler or a vibratory tumbler.

Rotary tumblers with soft rubber barrels and a frame made of metal are quiet and have a long lifetime if well cared for. They are the most popular choice for new and veteran hobbyists. With these tumblers, it takes about six weeks to process a batch of rocks, but they come out smooth and rounded.

Vibratory tumblers are a bit less popular; they are faster at what they do (1-2 weeks), but the stones do not come out rounded. Instead they are smooth, but stay angular. They are also more expensive, running around $200. You will spend closer to $80 for a rotary tumbler.

Rotary Tumblers

With a rotary tumbler, you place your rocks into one or more barrels. The additional barrels let you manage multiple batches at different stages or select different settings for specific types of rock.

The motor on the machine turns the barrels, and the rocks wear against each other until they are smooth. You can tumble a couple of pounds of rocks at one time. The plastic machines made for children work the same way, but they are loud and cheap because of their materials. The rubber is what keeps a rotary tumbler quiet and durable.

Vibratory Tumblers

Instead of a barrel, a vibratory tumbler has a bowl. You place the stones inside with water and some grit, and the bowl vibrates. The friction will smooth out the rocks, but they retain their basic shape instead of wearing into a rounded shape. An example of this can be seen to the right.

As you can see, there are advantages and disadvantages with both types of tumblers. For more delicate stones or those you want to retain their basic shapes, a vibratory tumbler is best’it is also fast, which is a bonus.

But for those you want more rounded, a rotary tumbler is better. Plus, a rotary tumbler is less pricey, which makes it a good choice for beginners. Read reviews and check warranties before you decide on your first rock tumbler, and follow the rest of our series on tumbling to learn what to do next!

Below you can find three of the best and most popular rotary rock tumblers through Amazon.com, simply click on the images below to take a look.

Rock Tumbling Guide Part 2: Tumbling Your Rocks

How do the rough rocks you pick up while you are rockhounding on the beach or in the hills turn into the beautifully polished, shiny and rounded gems you see for sale in rock shops? The answer is rock tumbling, and it’s something you can do in your own home with minimal equipment.

In Part 1 of our guide on tumbling, we introduced you to the two types of gemstone tumblers you can buy, rotary and vibratory tumblers. Rotary tumblers are less expensive, and slower, but they produce rounded stones with ease. Vibratory tumblers cost a bit more, work more quickly, and produce smooth stones which retain something more of their original shape.

If you have a rotary tumbler, you will be placing your rocks into a barrel which turns. With a vibratory tumbler, you will be putting the rocks inside a vibrating bowl. In either case, you need to get a batch of stones that are roughly the same hardness. They do not need to be the same size. And while it is easier to tumble stones of the same type all together, you can mix them up if the hardness is about the same.

Do not use stones which are cracked, because they will just break apart. Rocks with very strange shapes will often do the same. The following instructions are for rotary tumblers, the most common choice for beginners.

Coarse Grinding

This first step requires you to fill the barrel at least halfway, preferably 2/3 to ‘. Don’t add more than that. You will be placing water and grit inside the barrel as well, which will facilitate the process (much as it would be in a river or on a beach). The measurements above include the water and grit. Make sure you don’t exceed the weight capacity, which will be listed on the tumbler you buy.

The capacity is not just for one barrel (if there are multiple barrels); it is for the entire device. If the weight limit is 3 pounds, that is all you can put inside the tumbler. Note that if you have multiple barrels, you need them to be loaded evenly so that the barrels turn smoothly and the machine operates correctly.

Take a paper towel and clean off the rims of the barrel and lid so that the seal will be clean and dry. That way the seal will be totally effective. Now you’re ready to secure the lid. Start the motor, and the process will begin. For the first couple of minutes, you will want to hang around to ensure that the seal is on tightly. If it isn’t, you may notice leaking from the barrel. If you see this, stop the motor, pull off the lid, and wipe down the seal and lid again. Replace it, turn the motor on, and again check the status of the machine. If you don’t see any leaks, you can step away. Check back in a few hours. After that, check back once a day.

Tumbling is a long process. Yours will need to run 24 hours a day for about a week to complete this stage of the tumbling process. If you open your barrels and look inside during this time, you’ll notice muddy looking liquid called slurry. You shouldn’t have to open the barrels, though. At the end of the week, the slurry will look like mud. Resist the temptation to pour this stuff down your drain. The grit inside the mud will clog up your drain pipes.

Instead, place a colander over a plastic bucket, dump the mixture from the barrels inside, and allow the mud to drain through to the bucket. Run water over the stones to get all the grit off and get them clean. It is suggested you wear safety goggles so you don’t get grit in your eyes.

You need to be very careful to get the grit off the rocks. Why? Because it’s time for the fine grind next, and if you leave old grit on them, the old grit will not continue to smooth or shape the rocks, only put little scratches in them, and that you don’t want. You may need to repeat the coarse grind process 2-3 times before you are ready to proceed to the fine grind. Once again, discard any stones with cracks (or break them in half and throw them into the next batch to tumble).

Replace your old grit with new grit for repeated coarse tumbling so that you get the best results. What should you do if your new batch won’t fill the barrels halfway? Add more grit, or add plastic pellets. These will come in handy, so you will want to stock up on them.

Fine Grinding

Once you have completed your coarse grinds, you are ready to move onto the next step: the fine grind. Clean your rocks as well as the barrels and lids of your device. Do not allow any of the old slurry or grit to remain, or it will cause little scratches. It’s tough to get deep inside the barrel, but do your best with a long-handled brush (even a toothbrush can suffice).

This step is much like the previous step, except you are replacing your coarse grit with fine grit’it is a different kind of supply. Once again, you will want to make sure that the barrels are at least ? full, and then you will need to check and clean the seal and lid again so you can get the barrels firmly closed. Once you have done that, start up the machine, make sure that there aren’t any leaks, and then check on the machine again in a few hours. Once again, run the process for 24 hours a day, for at least a week, checking in on the machine each day.

After the fine grind is complete, you will be ready to proceed to the next step in the rock tumbling process, which is polishing your gemstones to shiny perfection!

Rock Tumbling Guide Part 3: Polishing Your Rocks

Want to learn how to make the gemstones you find in nature as smooth, rounded, and shiny as the ones you pick up in the tumbled rock section of a store? You can do it all at home using a rock tumbler.

Please look at the first two segments of our rock tumbling guide to learn about the types of rock tumblers on the market, which one is best for beginners, and the steps for the coarse and fine grind of your rocks.

After you have completed the steps outlined in part 2 of this guide, your rocks should be fairly smooth and rounded, but they still will not have that fancy shine that you will associate with tumbled rocks from a shop.

The step that gives you that shine is called polishing, and now you are going to learn how to complete this final phase in the tumbling process. After that, you can continue reading this guide to familiarize yourself with some of the supplies we have discussed in more depth.

Pre-polish

Assuming you have finished the fine grind on your stones, you will want to make sure that the stones are completely clean of debris from the tumbling process, and that the barrel has also been cleaned just as thoroughly. If there is any grit left on the rocks or in the barrel, that grit is not going to help your rocks get smooth and shiny; it is only going to cause very fine scratches to appear on your stones.

You will need to fill your barrel about 2/3 to 3/4 full. Since you are not using normal grit, at this point you will need to use plastic pellets designed for tumbling rocks to fill in the remainder of the space. Add water as you did with the other steps in the tumbling process to just below the rock level. Now you are going to get’extra fine grit,’which is also marketed as ‘pre-polish.’

Add that to your mixture in the barrel, check and wipe down the seal and lid, seal the barrel, and start the tumbler. Make sure it isn’t leaking before you walk away, and check on it a couple hours later. If the barrel is leaking, stop the tumbler, open it up, recheck the seal, wipe it down again, and reseal. After the process is running smoothly, you can check on it about once a day. Once again, you will need to leave your stones in the tumbler for about a week.

At the end of the week, you’ll see a mixture which looks a lot like tapioca pudding’just not as tasty. Get a colander, position it over a bucket, and pour your stones inside. Rinse them thoroughly to get all the grit off. Remember never to let the used grit go down the drain; it will clog.

Polish Test

There is no point proceeding to the polish unless your rocks are ready for it. To check, get a towel, and get it slightly damp. Now get your polishing powder and deposit a little bit of it on the towel. Use the towel to rub one of your gems, then check and see what happened. If the rock is shinier, then the batch is ready. Otherwise, put them back in the tumbler for another day or two and then perform the test again. Once the test passes, proceed to the polishing step.

Polish

Now you will be putting the rocks right back in the barrel again. Make sure everything is totally clear of grit again so nothing gets scratched, then put the rocks back in the barrel with enough plastic pellets to achieve the usual 2/3-3/4 volume level. Add in polish, about 4 tablespoons per three pounds. Wipe down the lid and seal as usual, close the barrel, press the start button, and do your usual checks to ensure everything is running properly and not leaking.

This step will have to continue for about ten days straight. When the rocks are dry, they should appear shiny, just as they do when they are wet. If they are not done within ten days, you can either try a couple more days of polishing, or you can take them out and attempt to burnish them. This can also correct their appearance should you spot a kind of film on the stones.

Burnish

This is a last step you can take to perfect the appearance of your polished gemstones. Clean out the barrel and the lid as well as the stones using a colander over a bucket, as you always do. Now, put the gems back into the barrel for one last tumble. Add a non-abrasive soap (Classic Ivory is a good choice).

The soap comes in bar form (liquid soaps are a no-no here; their oils can actually destroy the polish on your gems), so you will need to use a grater. Put the grated soap into the barrel with the plastic pellets, rocks and water using the same proportions you do with the polish. Let the machine run for a day or two, 24 hours a day.

After you’ve rinsed off your rocks and pellets again in the colander and separated them, you should have beautifully polished, shiny gemstones, as smooth and lustrous as any you would find in the store. You can do all of this on a pretty small budget. The most expensive part is the tumbler itself, and that can work great for years if you take good care of it.

In our next part, we will discuss the tumbling supplies you need in more detail (like the different types of grit), stones which can and cannot be tumbled and polished effectively, and rock tumbling tips and tricks to remember.

We’ll also introduce you to children’s tumblers. Tumbling rocks is a fun hobby to share with your kids, and even if you don’t have any, you may want to pick up a kids? tumbler instead of a hobbyist tumbler for your first batch if you are uncertain whether you will get into tumbling or not. It’s a lot cheaper, and while it will not run as well, it will introduce you to the process on a budget. If you know you want to purchase a hobbyist tumbler, check out part 1 of the guide if you haven’t already to learn all about vibratory and rotary tumblers!

Rock Tumbling Guide Part 4: Supplies Guide

Rock tumbling at home is an accessible and affordable hobby. The most expensive part is the rock tumbler. Once you purchase your tumbler though, you will still need to purchase a number of other supplies before you can get started. Rock tumblers need to be filled with various forms of grit, as well as tumbling media to cushion rocks. Following is a brief introduction to the supplies you will need to purchase.

• Tumbling grit. This is a type of abrasive sand, much like the sand in the ocean that helps to tumble rocks to smoothness. It’s usually made out of either carbide or silicon. When you place it inside the tumbler with your rocks in the appropriate amount, the grit tumbles against them and wears them down. You will need both coarse and medium grit, similar in consistency to coarse and fine sand.

• Pre-polish. You will also need fine grit, which has the consistency of powder and is referred to as ‘pre-polish? because of its role in the tumbling process.

• Polish. This is another powdery substance, generally made out of aluminum oxide, tin oxide, cerium oxide, and tripoli. This substance is used to produce the shine on stones which have been prepared with the pre-polish. Applying the polish is the last step required to make your gemstones shine.

For a quick start you can take a look at this package. It includes coarse and fine grit, as well as pre-polish and polish.

• Tumbling media. This phrase refers to ‘filler’ substances you will need later in the process. The rocks you put in your barrel are going to wear down over the weeks of tumbling. To continue to fill the barrel to the appropriate level, you will need to add in tumbling media to buffer the rocks. This usually takes the form of plastic or ceramic beads which fill in gaps between stones and provide support.Click here for a nice starter package.

• Rock breaking equipment. If you need to break the rocks because of their size or shapes (some rocks are too large or awkward to tumble as you find them), you will want to have a rock hammer, as well as heavy cloth, gloves, and safety goggles to protect your eyes from flying particles.

• Miscellaneous helpful items. You are regularly going to be rinsing off your rocks between steps before you put them back inside the barrels for the next tumbling round. For that you are going to need to have a colander and a bucket, because you cannot allow the grit to wash down the drain (it will clog your pipes). And of course you will need water, paper towels, and a basin. You also can benefit from a few other items, including a towel, toothbrush, tablespoon, knife, and bar of soap, specifically Ivory Soap.

If you already have read parts 1-3 of our guide on rock tumbling, you should be somewhat familiar with all of these items. If you need a refresher or you haven’t yet read parts 1-3, go back to find out how you will be using all of these supplies to tumble your rough rocks into a fine, smooth polish!

Rock Tumbling Guide’Part 5: Choosing the Best Rocks

If you’ve read the rest of the guide on how to tumble rocks, then you already know a lot about the different types of rock tumblers, as well as the other supplies you need for tumbling. You also should know the basic tumbling and polishing process, from start to finish.

But one subject which we have not yet discussed in detail is how to select the right rocks to tumble in the first place. Not all rocks are suitable tumbling candidates. Some can interfere with the process, or become damaged along the way.

Remember that tumbling rocks takes a lot of time and patience, not to mention electricity. You also use up some of your materials; you’ll probably be going through grit and polish pretty fast. So the last thing you want to do is mess up the process and end up with scratched or damaged stones instead of beautifully tumbled gems. You can ensure the tumbling process goes smoothly by checking through the rocks you plan to tumble first to ensure that they are all right for the job.

Stones That Are Great for Tumbling

In general, here is a list of gemstones which are commonly tumbled successfully: jasper, tiger’s eye, amethyst, agate, aventurine, carnelian, rose quartz, petrified wood, granite, moonstone, lapis lazuli, hematite, obsidian, amazonite, opal, diorite, and other types of quartz. Even among those rocks and minerals, not every type of stone is right for tumbling though. The stones which you are planning to tumble are referred to as tumbling rough. You want to stick to mostly quartz and agates.

When you decide to do a batch, you must make sure that the rocks in the batch are of roughly the same hardness. They do not all need to be the same type of stone, but do some research to make sure the hardness is comparable. Why? Harder rocks will chew softer ones to pieces, and softer rocks will do very little to help round out harder ones. The rocks need to be about equally hard so they can evenly and effectively round each other out.

Do use rocks of a variety of sizes, but avoid rocks which are too big. Aim for about 2 – 3 inches in length as a maximum.

If you don’t have access to your own rocks you should take a look at these rock tumbling stone mixes on Amazon.com. For between $10 and $20 you can find a great mix of stones that will tumble very nicely. Of course nothing beats the thrill of finding your own rocks and turning them into beautiful gemstones!

Stones You Should Not Tumble

There are some types of rock that do not tumble well. In particular, soft or porous stones are liable to fall apart. This is why you cannot effectively tumble sandstone, limestone, shale or coal, so avoid these rocks. Also avoid metamorphic rocks like mica that like to flake apart. Igneous rocks usually do not do well either because they are comprised of more than one mineral, and the different minerals wear down at varying rates, resulting in a rough and uneven job (or breakage).

There are several other types of stones you want to steer clear of:

• Unusually shaped rocks, particularly those with long protrusions. These rocks tend to break. They are not structurally sound. Besides, they are typically more interesting in their original form. Tumbling can help to bring out color and shine, but some stones are more interesting for their texture and their unusual formations. If you must tumble an unusually shaped stone, go ahead and break it first (more on that shortly).

• Rocks with deep cracks. These rocks may or may not break during the process, but be sure that the tumbling will not wear down or remove the crack. Cracks can trap grit as well, which you do not want. Break these rocks or skip tumbling them.

• Rocks with voids and pits. These too trap grit. You do not want this because the rougher grit you use in the beginning should not be brought into the fine grind or pre-polish steps of tumbling. All it does is create scratches on your gemstones which cannot be removed. Once again, break these or do not tumble them.

Breaking Down Tumbling Rough

If there are rocks you have with pits, cracks, or unusual shapes, and you want to tumble them, you have the option of breaking them. This needs to be done with care and attention to safety. Grab some safety goggles and put them on, along with industrial safety gloves. Wear heavy clothes to protect your body and a dust mask to protect your lungs.

You’ll also need something to use as an anvil. Rocks are often quite hard, so be aware they can damage softer surfaces. Do the job on a large, hard rock as an anvil, or purchase (or find) a steel block to work on.

You will also need a rock chisel and an appropriate hammer. Another thing you need is a round metal rod like the type used to reinforce concrete. Place this on top of your steel block or other anvil, then put the rock on top of that. Use the chisel to direct the energy of your blows into the rock (you are tapping the chisel, not the rock).

Do not smash the rock. The rod and chisel are helping you direct the force, and all you have to do to break the rock is compromise its structural integrity. Use precision (be a surgeon, not a butcher), and you will succeed quickly and easily in most cases.

Where to Get Tumbling Rough

Ideally, you’ll be able to find your own tumbling rough in the environment. Beaches, creeks, and hills, and many other locations contain rough gemstones which are ideal for tumbling. If you do not live in a place where you can quest for tumbling rough, you can visit a rock shop and order tumbling rough, or even buy it online.

When you purchase tumbling rough, you’ll usually get a bag containing stones of the same type that are the right size and shape for tumbling. Purchasing tumbling rough is also great for a beginner who is trying to learn the process without ruining a special batch of unique stones.

How to Tumble Gemstones Part 6: Rock Tumblers for Kids

Whether you’re planning on tumbling rocks yourself, or you have a child who is interested in getting into rock tumbling, you may have an interest in kids? rock tumblers. Why? They’re less expensive than standard rotary or vibratory tumblers (see part 1 of our series for more information), and they can help you or your child decide whether this is a hobby you’ll enjoy. It can be a good first step to take before making a more expensive investment.

How much will you spend on a kids? rock tumbler? Typically these kits are available for $50 or less. What’s great is that you not only get the tumbler for this price, but you also generally get all the other supplies you need to run at least one batch. That includes the tumbling rough, rough and fine grit, rock polish, and a basic set of instructions (you can find all you need to know by reading our guide though). You may even receive some jewelry mountings as part of the purchase.

What form do children’s tumblers typically take? Most are rotary tumblers, not vibratory tumblers (in fact, we haven’t actually found any vibratory tumblers for children, probably because those types of tumblers are more expensive than rotary tumblers). You usually get a single barrel.

A couple of well known brands include Rolling Stones by Natural Science Industries, Ltd. This company makes several similar tumblers called Smithsonian, SciEd, and Edu Science. Another company called Bowen Hill Ltd. manufactures tumblers called Discovery Planet and Elenco. With any of these machines, you can tumble about a half pound of rocks.

Drawbacks

There are a couple of drawbacks to these cheap tumblers. One of them is noise. Tumblers for kids are made out of plastic, and they are thus pretty loud compared to higher-quality tumblers made for adults out of better materials. They aren’t deafening, but you probably want to keep them out of the way in a basement or another location where you won’t have to constantly listen to the noise that they make.

The other drawback also relates to the cheap materials, and that’s the short life of these machines. Most of them will only handle a few batches before they break down.

Still, for $50, you can get a pretty good idea for what the process is like, and whether you want to invest $200 in a good tumbler and additional money on the rest of the materials. When you do decide to buy a more expensive tumbler, it can last for years if you maintain it properly.

Is Rock Tumbling a Good Activity for Kids’

Will your kids enjoy rock tumbling? Children who like geology and science will usually enjoy the satisfaction that comes with this hobby. As will kids who like art and jewelry. Rock tumbling takes weeks, and teaches patience, attention to detail, and cleanliness. So this is a great learning activity. It not only teaches geology, but skills which are important for everyday life.

How to Tumble Gemstones Part 7: Quick Tips for Success

We recommend you read our entire guide to tumbling gemstones so that you can learn the tumbling process in detail. We’ve tried to provide you with enough information that you will be able to tumble your first batch of gemstones without additional guidance (save to look up the proper size of grit particles for each step in the process).

Here is a summary of some of the most important things to remember during the process. Think of this as a cheat sheet with quick tips.

• Never try to tumble rocks which have deep cracks or pits, since these rocks can break apart during the process and cause problems. Also avoid trying to tumble unusually shaped rocks.

• Make sure that you thoroughly clean your stones and barrel between each tumbling step. It is essential you remove all the grit from each step before proceeding onto the next step. Leftover grit will not help you to complete the next polishing step, which always requires a progressively finer form of grit. It will only produce tiny scratches all over your stones which you cannot remove.

• Always put a bucket under your colander when you wash your gemstones. You do not want grit to get into your drain; it will clog your pipes.

• Check your barrel after the first hour when you start on a tumbling round to make sure it isn’t leaking. If it is, open it up, check and clean the seal again, and close it up again.

• Fill your barrel about 2/3-3/4. Do not under or over fill, or the process will not work properly.

• Always polish rocks which have about the same hardness as each other, even if they are not the same type of stone.

• Do not try to tumble rocks which are very porous or flake apart easily (like mica). These types of rocks will never become smooth. They will simply break.

• Before attempting to polish your rocks, do a quick polish check with a smidgen of polishing powder on a towel. If you do not see a difference, complete another round of fine grit tumbling before you proceed to the polish step.

• When you burnish your gemstones, always use a non-abrasive soap. Classic Ivory is recommended. Never use liquid soap as the oils can harm your gemstones.

• Take good care of your rock tumbler, and it will run great for a very long time. That means using it properly and taking time to clean and care for it between rounds. Good tumblers will last for years if they aren’t abused.

Tumbling and polishing gemstones requires a lot of patience, but the tumbler does most of the work. This is a great hobby for geologically inclined people, and is also excellent for jewelers who want to tumble gems to work with in their craft. Both adults and children can learn to tumble gemstones. Enjoy exploring the wonderful world of rock tumbling!

We hope you enjoyed this beginner’s guide to rock tumbling and are eager to give it a try yourself. If you have any questions about rock tumbling feel free to contact us!

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