The excitement of turning a jagged piece of stone into a gleaming gem or rock motivates rockhounds to polish stone after stone. Polishing rocks is a satisfying hobby, but the use of a rock tumbler to achieve the polished result is surprisingly unnecessary. With a few simple materials and some elbow grease, even the most novice rockhound can create beautiful polished stones and gems from a jagged collection.
At CMP Stonemason Supplies we have all you need.
What is a Rock Tumbler?
Rock tumblers are machines used to smooth and polish rocks. They are a popular tool used by jewellery, craft, and lapidary hobbyists for producing tumbled stones. Rock tumbling is also popular with people who want to discover the hidden beauty of rocks and minerals. Starting with a rough piece of rock and tumbling it into a beautiful, jewellery-quality stone is a very rewarding experience.
A brief history of rock tumblers
While nature has been tumbling rocks for millions of years, rock tumbling machines have only been around since the 1950s.
It was a way to take uncut rocks from nature, and turn them into gemstones that could be made into jewellery.
The process of rock tumbling gained popularity very quickly. By the 1960s, dozens of companies in the U.S had begun to manufacture tumblers.
Barrels of tumblers were first made out of paint cans and eventually evolved to use better materials like rubber and plastic.
While the industry started with dozens of manufacturers, only two were able to rise to the top and become the brands of choice: Lortone and Thumler’sThumler’s.
Both of these brands still exist today and cater to both rockhound hobbyists and lapidary professionals.
In addition to the professional-grade tumblers, there are a few brands of ”toy” tumblers that are perfect for kids. The more well-known brands are National Geographic and Smithsonian.
What to do with tumbled rocks
You’llYou’ll find that people love rock tumbling for a number of reasons.
While many folks love collecting a wide range of rocks to hold and display proudly, there are lots of other reasons why people get into rock tumbling.
Here are some of the more common uses for tumbled rocks:
- Jewellery making
- Various craft making
- Vase/planter filler
- Holiday decorations
Where to find rocks to tumble
Now that you know the basics of rock tumbling and what you can do with tumbled stones, let’s talk about how and where to find rocks.
What makes a rock good for tumbling?
It should be very hard, nonporous, and have a somewhat smooth surface (i.e., not gritty).
Some of the more popular types of rocks that fit these characteristics are agate and jasper – both common forms of quartz.
While you can buy any of these rocks online or at your local rock shop, I find it way more exciting to find them in nature (although not always realistic). For me, the thrill of the hunt is a big part of rock tumbling.
Agate is probably the most popular rock to work with because it’sits translucent and has so many unique patterns and designs. It’sIt’s a type of quartz and shines up to be real beauties.
In the United States, agate is typically found in Western states – particularly in Oregon, Arizona, Montana, Wyoming, South Dakota, and Michigan.
These rocks are typically found in coastal areas, lakes, and places with a past of volcanic activity.
It’sIt’s best to visit rocky beaches during low tide. Sometimes the agates will be laying right on top, and other times they’ll be buried between other rocks. Either way, they’re pretty easy to spot.
How Do Rock Tumblers Work?
The most popular tumblers have a barrel that is loaded with rocks, water, and abrasive grit. The abrasive grit is a granular material similar to the grains glued onto sandpaper. The grit is often labelled “coarse,” medium,” and “fine,” similar to the different grades of sandpaper.
The barrel containing rocks, grit, and water is placed on a motorized machine that rotates the barrel to tumble the rocks that are inside. As the rocks tumble, they grind against one another with particles of the abrasive grit caught between them. This action wears sharp edges off of the rocks and smoothes their surfaces. Tumblers that operate this way are known as “rotary tumblers.”
The rocks are typically tumbled for one or two weeks in coarse grit, one week in medium grit, and one week in fine grit, with a thorough cleaning of the rocks and the barrel between each grit size. Then the rocks are tumbled for one final week with water and a rock polish. After following this procedure, the rocks are usually transformed into brightly polished stones.
Using a rock tumbler to convert rough rock into polished stones can take as little as one week to as long as two months. The amount of time mainly depends upon the type of tumbler that you use, the type of rocks that you are tumbling and how picky you are about producing nicely-rounded stones.
Check our range of stone cutting tools for all of your working needs.
Rotary Tumblers – 4 to 8 Weeks
Most people who do rock tumbling use a rotary tumbler. With the typical rotary tumbler, you seal your rocks in a soft rubber barrel with a grinding compound known as “tumbling grit” and a little water. The barrel then rolls on the tumbling machine for about a week, and the rocks tumble inside of the barrel.
Most rotary tumbling is done using a four-step process: coarse grind, medium grind, fine grind (also called the pre-polish step), and polish. Each of these steps takes about one week. So, rotary tumbling generally takes about four weeks.
Some people who want superbly-shaped stones run the rocks in coarse grit for two, three or four weeks. Others inspect every rock after the first step and rerun any that could be improved with additional tumbling.
We are quite picky about our tumbled stones. We want them nicely rounded, and we want them free of surface blemishes. So, we almost always tumble them at least two weeks in coarse grit, and sometimes as long as a month when we have large pieces of pieces that have ugly shapes at the start.
A rotary tumbler is the most common type of rock tumbler and typically seals your rocks in a soft rubber barrel of which you also combine with your tumbling grit and a touch of water.
Once active, you can begin phase one of your tumbling. The tumbler shall then ”rotate”, tumbling the rocks. This process shall usually last for approximately a week before you move on to phase two.
There are a total of four phases, with each phase of tumbling using a different grit. The four grits should be used as follows: Coarse grind, medium grind, fine grind (pre-polishing) and polish.
Each phase shall last around one week, so you can expect on average for a complete run to take around four weeks before completion.
Some experienced hobbyists prefer to run their rocks in the coarse grit stage for two/three weeks to improve the shaping of their rocks, but this is entirely down to personal preference.
Alternatively, you can check the rocks after each run and pick out the individual rocks that you think could do with another run, while moving the rocks that have reached a satisfactory standard onto phase two.
Vibratory Tumblers – 1 to 2 Weeks
Most vibratory tumblers have a bowl that is rapidly shaken by a motor. This shaking produces a lot of friction between the rocks in the bowl and results in the rapid removal of material.
Most vibratory tumblers are run for 12 to 24 hours with medium grit. Then the spent grit and mud are washed from the rocks. This step is repeated until the rocks are nicely smoothed. This usually takes between three and seven days depending upon the type of rock and their starting condition. The rocks are then processed two or three days in fine grit (also called pre-polish), and two or three days with polish. So, vibratory tumbling generally takes between one and two weeks.
Why then doesn’tdoesn’t everyone use a vibratory tumbler? The first reason is that a vibratory tumbler costs about 50% more than a rotary tumbler. The second reason is that the grinding step of a vibratory tumbler “smooths” the rocks but does not “round” them like a rotary tumbler does (see rock photo at right). People who like rounded rocks use a rotary tumbler. Those who like angular rocks use a vibratory tumbler.
Vibratory tumblers can complete the task of polishing your rocks more quickly than rotary tumblers, but they are considerably pricier.
The majority of vibratory tumblers have a ”bowl” that is shaken by a motor abruptly.
Typically, a vibratory tumbler shall run from between 12 – 24 hours using a medium grit. The rocks are then cleansed, and the process repeated (multiple times) before you have wonderfully smooth rocks.
You can expect for this to take up to seven days, so the process is to be repeated a considerable number of times until you are satisfied that your rocks are ready to be moved onto the next phase.
Next up is the pre-polishing phase (the fine grit) which can take two-three days, and finally the polishing phase, which should take around the same amount of time.
Overall, this usually adds up to about two weeks in total.
While it may sound like an easy decision to opt for a vibratory tumbler, there are a few reasons that rotary tumblers are the most commonly purchased.
Firstly there is the issue of cost. You can expect to pay a significant amount more (think at least an additional 50%) for a decent vibratory tumbler.
Secondly, while a vibratory tumbler will smooth your rocks out, it will not round them the way a rotary tumbler can.
If you are a fan of well-rounded rocks, then you should probably opt for a rotary tumbler to achieve exactly this.
Types and Sizes of Rotary Tumblers
Rock tumblers are made in a wide range of sizes for different types of use. The three basic categories are described below.
Toy Rock Tumblers
The smallest and least expensive tumblers are toy tumblers with a plastic body and barrel. These machines typically sell for between $40 and $80 online or in local toy and craft stores. The advantage of these machines is their low price. However, they only tumble a few ounces of very small rocks, they have a very short life before they wear out, and the rocks tumbling in the plastic barrel make a lot of noise – noise is a very common complaint about toy rock tumblers.
Check out our list of the best rock cutting tools in the market.Check out our list of the best rock cutting tools in the market.
Hobbyist tumblers typically sell for between $70 and $300, depending mainly upon their size. Most are made with a metal frame and a quality motor designed to operate for years. They operate quietly because they have a rubber barrel or a metal barrel lined with rubber. They typically tumble between two and ten pounds of rock.
Hobbyist tumblers were first made in the late 1950s. Two brands, Thumler’sThumler’s Tumblers and Lortone are still being manufactured today with very little change to their basic design. Successful products persist in the marketplace. Many people received a hobbyist tumbler by Thumler’sThumler’s or Lortone as a gift when they were a child and are now using that same tumbler with their grandchildren!
Instead of being made with plastic, hobbyist tumblers are made from metal and other durable materials. Thumler’sThumler’s and Lortone parts are still manufactured today. Most of their tumblers can be repaired or refurbished with readily-available parts.
Commercial Rock Tumblers
Commercial tumblers are large machines that can tumble a few dozen to a few thousand pounds of rock at a time. They cost several hundred to many thousands of dollars and are used almost exclusively by people and companies who are in the business of producing tumbled stones.
How to Polish Rocks & Gems Without a Rock Tumbler
Cleaning the Stones
Fill a bucket with hot, soapy water and clean away all the dirt and residue from the rocks. Use an old toothbrush to get into any crevices and to remove stubborn bits of dirt or grime.
Grinding the Stones
Use a handheld rotary tool, often called a Dremel tool, to begin grinding the stones and gems into shape. Make sure you are wearing protective eyewear and gloves for this. Grind down sharp edges and crevices to help make sanding the stones and gems a little easier.
Sanding the Stones
Sand the stones and gems for shaping. Begin with a coarse grain of sandpaper, and moisten the paper with water. Begin sanding until most of the rough edges begin to become smooth and rounded or until you see the desired shape of the rock. Be discriminating with your grain of sandpaper, as some stones and gems are softer than others. You may find that softer gems or stones do not require the coarsest grain of sandpaper.
Sand the stones and gems again to prepare them for polishing. Begin with medium grain sandpaper, and sand the rock down to both its desired shape and smoothness. As you see your desired results, use lighter grain sandpaper, finishing with the ultra-fine grain.
Polishing the Stones
Apply the finishing polish to the stones and gems. Using a heavy fabric such as denim, polish the rocks until they begin to shine or show lustre. At this point, you may choose to either continue polishing with the cloth, or you may coat the stones and gems with mineral oil or commercial rock polish. Allow them to dry.
What Types of Rock Can Be Tumbled?
Most rocks will not perform well in a rock tumbler; however, a few types of rock can be successfully tumbled by a beginner if the rocks are carefully selected. These easy-to-tumble rocks include agate, jasper, chalcedony, and petrified wood. All of these materials are composed of microcrystalline quartz, which is a very hard, tough, and durable material that accepts a very bright polish.
Rocks that are worth tumbling are free of voids, cavities, and fractures. They also have a non-granular texture. Many people are lucky enough to live in a location where these rocks can be collected, always with the permission of the landowner, in streams or beaches or scattered on the surface of the ground. If you do not live in one of these locations, then good material for tumbling can easily be purchased at a rock shop or from a website that sells rock tumblers and rock tumbling supplies.
Most rock tumbler kits are supplied with a small jewellery kit that you can use to make a couple of gift items from your first batch of tumbled stones. Keychains, pendant necklaces and other small jewellery items make great gifts.
Tumbled stones can also be used for many other things. They can be used as accents or ground cover in potted plants, glued around the edges of picture frames, used as game pieces, dressed up with eyes and antennae to make rock critters, used as vase fillers, placed in a bowl and used as a cosmetic brush holder. The accompanying images show a few of the things you can do with tumbled stones.