What is Tumbling Rough?
"Tumbling rough" is the name used for the rock material that is placed in a rock tumbler to produce tumbled
stones. Agate, jasper and varieties of quartz are the most commonly used materials. Many other materials
will produce nice tumbled stones. However, nice tumbled stones can only be made using materials with
certain characteristics. Most rocks do not have these characteristics and will not produce nice tumbled
stones. Because of this, tumbling rough must be selected with knowledge and care.
Characteristics of Good Tumbling Rough
The types of rocks that perform best in a rock tumbler are hard, tough rocks with a smooth texture. "Hard"
means that they are not easily scratched. "Tough" means that they are not easily broken. "Smooth texture"
means that the rocks are not granular, porous or internally fractured.
Agate, jasper, and quartz are hard tough rocks. But, before tumbling they must be inspected to remove
pieces with pores and fractures. Tumbling poor quality materials is a waste of time, grit, and
electricity. A rock that sheds particles or carries grit into the polishing step can ruin the polish
on every stone in the barrel.
Some people think that a rock tumbler is machine that will turn junk rock into nice polished stones.
That rarely happens. If you put junk in you will get junk out.
Agate and Jasper - Favorite Roughs
Agate and jasper are two materials favored above all others for rock tumbling. They are favored because
they often have beautiful colors and patterns. Agates and jaspers often have beautiful bands, plumes,
dendrites and other interesting patterns.
Silicified wood (also known as "petrified wood")is a variety of jasper. It is a very popular tumbling rough
and is found in many parts of the United States. It is colorful, often has interesting wood patterns and
produces beautiful tumbled stones.
Agate and jasper usually shape nicely in a rock tumbler and polish to a bright luster. If you use these
rocks in your tumbler and elimiate low quality pieces, you should be rewarded with nice tumbled stones.
Colorful agate and jasper, sized for use in a tumbler, usually sells for about $5 to $10 per pound. Material
with premium color and pattern can cost a little to a lot more. The amount depends upon color, pattern
and the material's popularity.
Varieties of Quartz
There are many types of quartz and it occurs in all colors of the spectrum. These varieties of quartz are
favorites for tumbling: rose quartz (pink), smoky quartz (brown), amethyst (purple), lemon quartz (yellow),
peach quartz (orange) and crystal quartz (clear). The colors are caused by trace amounts of impurities or
defects within the crystal structure of the quartz.
Quartz is hard, tough, and usually has a smooth texture. However, it often requires a little more care during
tumbling than agate and jasper. The care required is to make sure that the pieces are not tumbled roughly.
If there is too much action in the barrel, pieces of quartz can be chipped, bruised or fractured. This damage
can be avoided by filling the tumbler to the proper level and adding small ceramic media or small pieces of
rough to reduce the severity of impacts in the barrel.
Aventurine Quartz and Others
Some specimens of quartz contain inclusions. Aventurine is a good example. It contains tiny particles of mica.
Light that enters the stone strikes the mica particles and reflects from them. This gives aventurine a sparkling
luster. Aventurine has the characteristics of a good tumbling rough and produces nice tumbled stones.
It is usually costs about the same as nice agate and jasper.
Tiger's eye forms when the mineral crocidolite is replaced by quartz. Crocidolite is a fibrous material and the
parallel quartz replacements reflect light. Round polished pieces of tiger's reflect light like a chatoyant
"eye". Many people think these eyes resemble the eyes of a cat. That is how tiger's eye received its name.
The varieties of quartz mentioned above are often seen for sale as tumbling rough. They are usually inexpensive,
costing between $5 and $10 per pound for prepared rough. Rough of premium color and condition can sell for
Size of Tumbling Rough
Pieces of rough used for tumbling usually range in size between 1/4 inch and 3 inches in size. Small tumblers
with a two or three pound capacity barrel work best when tumbling rough up to about 1 1/2 inch in size.
Tumblers with a six to twelve pound capacity barrel can tumble rocks that are up to about 2 1/2 inches in size.
Only two or three large rocks should be added to a load.
Some people collect or purchase large pieces of rough that weigh several pounds each. These large pieces of
hard, tough rock are difficult and dangerous to break. We don't recommend that activity, even to people who
have lots of rock-breaking experience.
We recommend collecting or purchasing rocks that are properly sized for your tumbler. Lots of rock shops and
websites sell rock that is specially sized for tumbling. Nice tumbling rough is also offered for sale at many
gem and mineral shows.
If you have large pieces of rough the best way to reduce their size is to take them to a rock shop with a rock
crusher or a rock trimmer. Some rock shops will crush a few pounds of rocks for a fee of a few dollars. You
will get back a bucket that contains your crushed rock. You can then take it home, wash it, inspect the pieces,
and discard those that are poor candidates for tumbling. Some waste and undersized rock should be expected.
Before You Collect Tumbling Rough
Many people who run rock tumblers enjoy collecting their own rough. Collecting tumbling rough can be a great
activity for family and friends. But, before you go out collecting, you need to know a few things about property
ownership and mineral rights.
In the United States, all land, rocks and minerals are owned by a person, a company, an organization, or the
government. So, before you enter any property, dig, or remove anything be sure that you have explicit permission
for what you plan to do, what you plan to remove, and what you plan to do with anything that you remove. If you do
these things without permission you could be arrested for vandalism or theft.
Rock and Mineral Clubs
There are many rock clubs located in all parts of the United States. These clubs often have organized collecting
trips. Being a member of one of these clubs is a great way to learn and a great way to obtain access to excellent
collecting areas. These clubs often have swap meets where you can bring materials that you collected and trade them
for different materials that another member has collected.
Fee Mining Sites
Finally, across the United States there are dozens of small mines that allow visitors to pay a fee, look for rocks
and minerals, and keep whatever they find. These can be fun places to visit and if you know what you are doing you
might be able to find some really nice specimens. Skill and luck are both important parts of finding nice specimens.
So, while you are there, pay attention the methods of successful people. They are often willing to provide advice
that will improve your collecting skills.
Now you are ready for Rock Tumbling Grit
|About three pounds of tumbling rough. The materials shown here are all quartz and include: tiger's eye, amethyst, green and blue aventurine, rose quartz .
| Don't try to tumble rocks with protrusions, voids or fractures. They usually don't tumble well and they often break during one of the final steps and scratch every other rock in the barrel. Throw them away or break them into smaller pieces.
| Rocks and Minerals Commonly Tumbled