In addition to a rock tumbler you will need some rock tumbling supplies. These include: tumbling rough (rocks to tumble), tumbling grit, rock polish, tumbling media (material to cushion the rocks or fill the barrel to the proper level).
All of these are necessary and learning about them will improve your tumbling success and enjoyment.
The photo at right shows the contents of a rock tumbler kit that is sold with all of the needed supplies. Pictured are the tumbler (right), rough rock (front) and bags of grit, and bags of polish and pellets (left).
We provide brief descriptions of these items below with links to more detailed articles and photos.
Rocks for Tumbling (aka Tumbler Rough)
Tumbling rough is crushed or broken rock material that you hope to get polished in a tumbler. The quality of the finished stones that you produce will be mainly determined by the quality of rough rock that you place in the tumbler.
Most rock will not tumble to produce a highly polished gem. You must use the right types of rock. Agates, jaspers, flints and quartz minerals are the most commonly tumbled rocks. These are hard, solid materials that are free from voids and grainy textures. Rocks such as sandstone, siltstones, shales and schists are too friable to tumble. Rocks such as limestone and dolomite will round in a tumbler but will not take a polish. Do research, experiment or ask an experienced person if you are uncertain.
Many people live or travel where good tumbling rough can be collected. If you are one of those people you are very fortunate! Most people live where good tumbling rough is hard or impossible to find so they purchase most of their tumbling rough. It's great to collect your own rough but there is nothing wrong with purchasing it! Even people who can collect their own should buy a little exotic material to bring a little adventure to their hobby. There are many rock shops and internet sites where you can purchase wonderful, colorful varieties of rock that you would probably never find in a lifetime of fieldwork.
Learn more about tumbling rough.
Tumbling grit is an abrasive sand or powder - usually made of silicon carbide. It is placed in the tumbling machine with rough rock. The grit is much harder than the rocks that you tumble. As the rocks move in the tumbler the grit gets caught between them and wears them away. This is an abrasive action similar to sand paper.
Tumbling grit comes in different sizes such as 60/90 (coarse), 120/200 (medium) and 500 (fine). Coarse grit is a sand-size material and is the most abrasive. It is used in the first step of the tumbling process to round the sharp edges off of the rough. Medium grit is the size of fine sand. It is used to smooth the surface of the rounded rocks. Fine grit is a powder-size material that is used as a pre-polish. It removes scratches left by the medium grit and prepares rock surfaces for polishing.
Learn more about tumbling grit.
Rock Polish and Pre-Polish
Rock polish is an abrasive powder that buffs the smooth surfaces of prepared rock to a high polish. It is what produces the shiny luster on the surface of finished tumbled stones. Several different compounds are used as a rock polish. These include: aluminum oxide, tin oxide, cerium oxide, tripoli and others.
These are used as the final step of the rock tumbling process.
Sometimes a 500 grit silicon dioxide or a 500 grit aluminum oxide are referred to as a pre-polish. This step removes all scratches left by the 120/220 grit and prepares the surface of the rocks for the polishing step.
Learn more about rock polish.
Tumbling Media - Pellets, Beads, Etc.
Rocks tumbling in a barrel from several days to a week take a lot of pounding and abuse. The repeated impacts can cause some of the rocks to chip, bruise or crack. This is expecially true if a batch of large rocks is being tumbled with no small rocks between them to buffer their actions. To protect the rocks - especially in the fine grind and polishing steps - plastic pellets or ceramic beads are often added to the tumbling barrel. The soft plastic beads can provide cushion the impacts and the ceramic beads can fill the spaces between the large rocks and provide support.
Learn more about tumbler media.
Other Handy Items:
A number of other items will be needed while tumbling. Here is a list of what we keep on hand or have easy access to while tumbling. You might not need all of them or might add others to the list.
* Paper towels
* Household oil
* Colander or screen
* Old towel
* Measuring tablespoon
* Bar of Ivory Soap
* Rock hammer
* Safety goggles (required for breaking rock and cleaning rocks)
* Gloves (required for breaking rock)
* Heavy cloth (required for breaking rock)
* Extra barrel for polish step
* Extra grit, polish and pellets
* Extra tumbling rough
* Small scale
* Old toothbrushes
Now you are ready for Tumbling Rough
Rock tumbling kits are a very popular and easy way to get started. These kits include the tumbler and all of the supplies that you will need to tumble one or two batches of rock such as grit, polish, and rough rock.
About four pounds of tumbling rough of various sizes and coarse grit ready to load into a six pound tumbler barrel. Tumbling different sizes of rough in the same batch produces better results than tumbling rock of a single size. If we filled the tumbler with the 1 to 2 inch-size rock on the left there would be very few points of contact between the rocks during the tumbling process. Mixing in smaller rock fills the spaces between the large particles, increase the amount of abrasion and delivers grit to all surfaces of the large rock.
Tumbler grit is silicon carbide in granular or powdered form. It is sold in different sizes. The 60/90 grit is normally used in the first step of the tumbling process. It is sand-size silicon carbide used to grind and shape the rough rock. The 120/220 grit is used in the second step. It removes scratches left by the 60/90 grit and does minor shaping. The 500 grit is used as a prepolish. It removes scratches left by the 120/220 grit and prepares the surface of the rock for polishing.
Several different compounds are used for the polishing and pre-polishing steps of the rock tumbling process. tin oxide, tripoli, aluminum oxide and cerium oxide are some of the most commonly used polishing compounds.
Tumbling media is a material placed in a tumbler barrel with rough rock. The purpose of the media is to reduce the intensity of abrasion between the tumbling rocks or to act as a filler when tumbling an amount of rock that is less then the capacity of the barrel. The small round beads in this photo are plastic pellets used for cushioning and the white cylinders are ceramic media used as a filler. The pellets are about 3/16 inches in diameter.