What are Tumbled Stones, How are they Made?

Tumbled Stones Produced in a Rock Tumbler

Tumbled stones are small pieces of rock or mineral that have been smoothed, rounded, and polished.

The process begins when rough pieces of stone of a similar shape and size are placed in a rock tumbler. The barrel or drum is then filled with water, sand, and coarse grit.

As the barrel (or drum) slowly rotates, the stones gradually lose their rough edges and become smoother and more rounded.

The coarseness of the grit determines the smoothness of tumbled stones. Coarse grit is used initially but is then replaced with medium, followed by fine grit.

The grit works like sandpaper. The finer the grit, the smoother the finish.

The final stage in producing tumbled stones involves polishing, which is done by replacing the grit with a polishing agent, usually a fine powder.

The length of time required to produce tumbled stones can vary from a few days to several months, depending on several factors. These include the size of the rock tumbler, which can range from a small hobby machine to an industrial-sized tumbler, as well as the size and hardness of the rocks or minerals being tumbled, how full the barrel is, and the coarseness of the sand or grit.

Using a rock tumbler to produce tumbled stones mimics a natural process. When fragments of rock beneath or near a body of water are gently moved back and forth, the motion of the water causes them to rub against each other and the surrounding sediment.

Sediment consists of small pieces of rock, minerals, and the remains of plants and animals.

Over long periods, rough fragments become smoother and more rounded. The stones we know as beach or river pebbles are essentially tumbled stones.

Most, but certainly not all, tumbled stones tend to be minerals.

Making your own tumbled stones can be fun and rewarding. All the information you need to get started can be found here.

Not all stones being sold as "tumbled stones" have been produced in a rock tumbler. Some are cut and polished by hand. This practice has only started in the last few years.

It's usually quite easy to tell when tumbled stones have been cut and polished by hand because their shapes and sizes are very similar. These stones typically come from India and other countries in Asia.  

Tumbled stones shaped like cubes, spheres, or ovals will not have been produced in a rock tumbler. Rough stones being rotated in a drum or barrel are unlikely to come out perfectly round, oval, or square, possibly with the exception of the odd one or two.

Tumbled stones produced in a rock tumbler are rarely the same shape or size and often have minor surface imperfections and anomalies.

The tumbled stones in this photo would have been cut and polished by hand.
The term "tumbled stone" is now used to describe any stone that looks like a "tumbled stone," regardless of how it's been produced.

Most "tumbled stones" are produced in South Africa, India, Pakistan, and China. Part of the beauty of stones produced in a rock tumbler is that each piece is unique with a slightly more natural appearance.

Tumbled stones cut and polished by hand are far easier to fake than those produced in a rock tumbler. Most fake crystals, rocks, and minerals are produced in China. 

Natural stone, glass, plastic, resin, or any number of other materials can be used to produce fake stones.  Colour, texture, and optical phenomenon such as sparkle or iridescence can be produced or enhanced using a variety of techniques.