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 Glossary of Rock Tumbling Terms 

rock tumbling grit and polish

Abrasive: a substance that wears down or rubs away by friction, commonly called tumbling grit.

Amplitude: a measure of voltage indicating motor speed.

Barrel: the barrel or hopper is the part of the rock tumbler where the rocks are contained while being polished.

Bowl: a barrel shaped like a bowl. Usually the barrel of a vibrating rock tumbler.

Burnish: to make smooth by rubbing. Also used to refer to ingredients, such as soap flakes, used in the final polish phase to make the rocks glossy.

Cabochon: a polished rock that curves outward and has no facets. This term, also spelled cabochon, refers to the cut of a rock as well, as in "cabochon cut" (pronounced CAB-a-Shawn).

Capacity: the maximum volume of the inside of the rock tumbler barrel.

Ceramic media: filler made from small bits of ceramic. This type of media is easier to clean because grit does not become embedded in it. Also referred to as rock tumbling media.

Charged Barrel: a loaded barrel.

Contaminant: anything that does not belong in the barrel with the rocks; most commonly it is old or inconsistent grit carried over from reused filler.

Crevice: indentation, crack, cleft, or fissure in the surface of the rock.

Cubic feet: an expression of volume used to measure the inside of the rock tumbler barrel.

Cushion a load: to add filler, such as plastic pellets.

Cyclonic effect: when a vibrating tumbler moves the material around the inside of the bowl and down the center.

Cylinder: a rotating chamber with a cylinder shape. Another name for the barrel.

Drum: the barrel of a rotary tumbler.

Dry polish: to polish stones in a rock tumbler without using water. A polishing agent, such as cerium oxide, might be mixed with oatmeal, for example.

Facet: a flat surface on a stone, usually made by cutting. Facets can occur naturally on crystals.

Faceting: to cut facets on a stone. Sometimes this makes for interesting shapes when done before tumbling.

Filler: a non-rock substance used to balance out the load and cushion the rocks inside the tumbler. Filler media can be plastic, ceramic, or small stones that have the same or lesser hardness as the rocks being tumbled. Also referred to as rock tumbling media.

Finishing: another term to describe polishing.

Fragile stones: stones with a low Mohs hardness, for instance talc, gypsum, and calcite. Fragile stones are not recommended for rock tumbling.

Gem: precious and semi-precious stones and minerals, cut and polished and highly prized. Often worn as jewelry.

Geologist's hammer and pick: specialized hammer and pick tools used to break rocks.

Geology: the study of the earth's crust including, especially, rocks and minerals. A geologist is someone who studies rocks.

Grit: tiny rough granules. Rock tumbling grit is essential. Always use fresh grit because polishing makes it dull and useless.

Hardness: how hard a rock is. This is measured by scratching.

Hopper: a funnel-shaped barrel on a rock tumbler.

Inlet and Outlet rinsing ports: openings in the barrel or bowl which allow water to come in the inlet port and exit through the outlet port. This is convenient because it means that the slurry does not have to be removed in order to rinse the stones being polished in the tumbler.

Jewel: a precious stone or gem.

Kinetic Activity: energy created by motion.

Lapidary: a gemstone dealer, rock polisher, or stone cutter. This word implies precision and refinement and is not formally used for rock tumbling hobbyists who enjoy smoothing out a stone's natural curves.

Load: the contents in the barrel of the rock tumbler, usually consisting of rocks, abrasive, filler, and water. The load must be at least half of the barrel capacity and never more than three-fourths of the capacity.

Lubricant: a substance that reduces friction. Water is most commonly used as a lubricant for rock tumbling.

Media: also called tumbling media, is non-rock substance used as filler to cushion the rocks from the constant impact inside the tumbler barrel.

Mesh: a network-type fabric or structure, as in wire mesh, that acts as a net or screen. Mesh is used to measure the granule size of grit and it is also a term used to describe the size of grit, for instance, a grit mesh of 60/90. Coarse grit falls through larger holes in the mesh than fine grit, so it is said to have a larger grit mesh.

Mohs Hardness Scale: a relative scale of hardness used for rocks. Created by Friedrich Mohs in the early 1800's, it is a list of ten rocks from talc to diamond. If a rock scratches one of the rocks on the list, it is harder than that rock and you have found the same hardness when they scratch each other. Stones with a hardness of 5 to 7 are perfect for polishing, such as agate tumbling rocks (hardness of 7).

Multi-Barrel Polisher: a rock tumbler with two barrels which allows two polishing phases to run concurrently.

Particles: small granules of grit.

Pits: holes or cavities in a rock that range from small pin-prick size to sunken depressions or craters. Rocks with pits will collect the grit in the tumbling process and require extensive cleaning between polishing phases.

Plastic Pellets: a type of filler preferred by some because it can float, allowing for easy separation from the tumbled rock. Rock tumbling pellets should be reused with the same size grit because it becomes embedded in the plastic.

Polishing Compounds: a substance used to smooth and shine the surface of the tumbled rocks. Alumina, Aluminum Oxide, Cerium Oxide, Ferric Oxide, and Tin Oxide are polishing compounds. Soap flakes can also be used.

Polishing stages: there are at least two phases of rock tumbling necessary for a proper polish: the pre-polish stage and the polish stage. It's important to understand how and when to use rock tumbling grit and polish.

Polyethylene: a sturdy resin material used in high-quality kitchenware, containers, and tubing. Rock tumbler barrels made with polyethylene provide an excellent combination solid construction with good shock absorbency.

Preform: a stone that has a shape cut into it before it is polished. This gives some control over the final outcome, for instance, a stone can be cut into a rough tear drop shape and then polished to perfection.

Quarry: a place in the earth that is dug out for the purpose of excavating rocks.

Rating: the number given for grit according to its mesh or particle size. The larger the grit rating or number, the smaller the particles. Grits are often sold as part of rock tumbler kits.

Rinsing Port: a place of entry and exit for water to flow through the barrel and rinse the stones inside.

Rock: a naturally formed mineral matter of varying hardness. This term can be used for large formations as well as the small pieces we collect to polish such as agate and jasper. Interchangeable with stone.

Rock Hound: a nickname for rock collectors who are dogged in their pursuit of good rocks to polish.

Rock tumbling: polishing stones with a rock tumbler.

Rotary Tumbler: a traditional type of rock tumbler, also called a rotary drum tumbler, which is designed to rotate the rocks inside of a barrel.

Rough stones: raw, unpolished pieces of rock. Also called rock for tumbling.

RPM: rotations per minute.

Silicon Carbide: a type of grit made from silicon. It is also known as silicon sand and those in the know often abbreviate it as SiC.

Slurry: the mixture of water, grit, and stones created inside a rock tumbler.

Sonic: using sound waves.

Stone: earthy or mineral matter. A small rock or piece of rock. Interchangeable with rock.

Thermal protected: designed to protect from over-heating.

Tumbler: a container that revolves, rocks, or vibrates in order to polish stones contained within it.

Tumbling rough or tumbling rocks: small, broken rocks waiting to be polished in a tumbler.

Variegated: having streaks or marks of different colors. Agate is a common stone that is variegated.

Vibrating Tumbler: a style of rock tumbler that uses vibration instead of rotation to polish stones. Also called a vibratory tumbler, this style of tumbler completes the polishing phases in less time than the traditional rotary tumbler.

VPM: vibrations per minute.

Weight Allowance: the maximum amount of weight permitted in the rock tumbler barrel for optimum performance.