Rock Discoveries

Unlocking The Secrets of Rock Tumbling Grit

Rock Tumbling Grit: Everything You Need to Know

Rock tumbling is a process of transforming rough rocks into smooth, polished stones with the help of an abrasive substance called rock tumbling grit. This grit, which acts as sandpaper, removes rough outer layers of rocks, revealing their inner beauty.

In this article, we will cover everything you need to know about rock tumbling grit, including what it is, its make-up, toxicity, reusability, alternatives, and how to dispose of it. What is Rock Tumbling Grit?

Rock tumbling grit is an abrasive substance that is used to sand and polish rocks during lapidary work. This grit is available in various sizes that represent different levels of coarseness.

The size of the grit refers to the number of granules per square inch. The smaller the number, the coarser the grit.

This granular substance is made of silicon carbide, an artificial abrasive that has sharper edges compared to natural abrasives such as sand or quartz. What is it made of?

The Mohs hardness scale measures the resistance of a mineral to being scratched. The scale ranges from 1 to 10, with 10 being the hardest.

Silicon carbide has a Mohs hardness score of 9-9.5. This means that it can easily scratch minerals with a score of 7 or less, making it effective in removing outer layers of rocks. The artificial nature of silicon carbide gives it sharper edges, which make it more efficient in sanding rocks.


According to the Occupational Safety and Health Administration (OSHA), silicates, which are found in silicon carbide, can cause respiratory diseases such as silicosis. Silicosis is an incurable lung disease caused by inhaling silica dust.

It can lead to nose and eye irritation, pneumoconiosis, tuberculosis, and cancer. As a result, it is important to use protective gear such as masks, gloves, and goggles when handling rock tumbling grit.


Rock tumbling grit can be reused multiple times during the tumbling process. When tumbling rocks, the grit mixes with water and rock particles, creating a slurry-like consistency.

As the grit loses its sharpness and becomes dirty, it is time to move to the next tumbling stage and use a fresh batch of grit. The quality of the grit is determined by its sharpness and consistency, which can be observed using a loupe.

There are many brands of silicon carbide grit available in the market, and Amazon has several grit recommendations based on the type of rock that is being tumbled.


While silicon carbide grit is the most commonly used abrasive for rock tumbling, there are alternatives. The alternative grits can be used as long as they have a higher hardness score than the rock being tumbled.

For example, popular alternatives are chalcedony, quartz, jaspers, agates, carnelians, and petrified wood. Beach sand, silica sand, sinterblast, aluminum oxide, and bauxite ore can also be used as alternatives.

Disposing of Rock Tumbling Grit

The disposal of rock tumbling grit should be done carefully to avoid harming the environment and plumbing blockages. The excess grit should not be dumped in a garden hole because it can suffocate plants.

The dust particles should also not be inhaled because they can cause respiratory problems. The grit can be disposed of in a trash bin, gravel driveway, or be used as fertilizer.

Plumbing blockages can be avoided by flushing the used grit down the toilet while running plenty of water.

Rock Tumbling Stages

Tumbling rocks follow four stages: coarse grit, smoothing, finest grit, and polishing. Each stage has its specific function in the transformation of rough rocks into smooth, polished stones.

Stage One: Coarse Grit

The first stage uses coarse grit, the largest granule size, to remove the rough outer layer of the rock. This stage is ideal for harder and larger rocks and can last for 2-3 days.

Using water in the tumbling bowl helps prevent the dust from accumulating and makes the process more efficient. Stage Two: Smoothing

The second stage reduces the size of the scratches and imperfections left by the rough surface of the rock.

This stage involves using a finer grit size that will decrease the pits and surface cracks. The grinding down of the rough edges also happens in this stage.

Stage Three: Finest Grit

The third stage uses the finest grit size to remove the visible scratches and indentations. The rocks will become very smooth during this stage.

Water is still used in the process to flush away the grit and keep the rocks clean.

Polishing Stage

The last stage adds shine and luster to the rocks through the use of a polishing compound. A plastic pellet is added to the bowl to help prevent the rocks from scratching each other.

The polishing process is fairly quick and replaces the grit slurry with the polishing compound.


In conclusion, rock tumbling grit is a key component of transforming rough rocks into polished stones. The grit’s composition, use, disposal, and safety should be considered when investing in lapidary work.

The four stages of tumbling allow the rocks to go from coarse to polished, revealing their inner beauty. Whether for a hobby or a business, rock tumbling can provide a rewarding and satisfying experience that results in beautiful natural works of art.

In summary, rock tumbling grit is an integral part of the lapidary process, transforming rough rocks into beautiful and polished stones. From its composition to reusability, toxicity, alternatives, and disposal; recyclability, the article has provided an informative guide to rock tumbling grit.

With a detailed account of the four stages of rock tumbling, a beautiful natural work of art is attainable. Here are some of the FAQs on rock tumbling and their answers that will help make the process less intimidating:


Is rock tumbling grit safe to use? Yes, rock tumbling grit is safe to use, but precautionary measures should be taken to avoid respiratory diseases such as silicosis.

2. What are the alternatives to silicon carbide grit?

Other abrasives such as chalcedony, quartz, jaspers, agates, carnelians, petrified wood, beach sand, silica sand, sinterblast, aluminum oxide, and bauxite ore can be used as alternatives to silicon carbide grit. 3.

How many stages does rock tumbling have? Rock tumbling has four stages: coarse grit, smoothing, finest grit, and polishing.

4. Can rock tumbling grit be reused?

Yes, rock tumbling grit can be reused multiple times but its effectiveness decreases with each use. 5.

How should rock tumbling grit be disposed of? Rock tumbling grit should be disposed of in a trash bin, gravel driveway, or used as fertilizer.

Do not dump in a garden hole as it can suffocate plants.

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