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Cerium Oxide Polishing Compound

One of the Original Rock Tumbler Polishes

Optical grade cerium oxide polish
Optical grade cerium oxide polish

What Is Cerium Oxide Polish?

Cerium oxide was one of the first polishes to be widely used in rock tumbling and many people still use it today as their first choice of polishes. It produces a bright polish on agate, jasper, quartz, petrified wood, obsidian, feldspar minerals and just about every rock, mineral and glass that is processed in a rock tumbler. Cerium is a chemical element and in combination with oxygen it is known as "cerium oxide" with a chemical composition of CeO.

How much to use?

In rotary tumblers we recommend about two tablespoons of cerium oxide per pound of material in the barrel (rough rocks plus ceramic media). In vibratory tumblers we recommend about one tablespoon of polish for every 2 pounds of material in the bowl.

Preparation for polishing:

Most quality tumbling roughs that have been run through a fine grit step (500 or 600 grit silicon carbide) are ready for polishing. When we tumble, we go straight from fine grit to polishing.

However, some people like to run an extra fine grit step (1000 mesh silicon carbide) before polishing. This might improve the luster of your polished stones, or reduce polishing time, but it is possible to get great results without this extra fine grit step.

How long to polish?

In a rotary tumbler most materials will tumble to a bright polish with cerium oxide in about seven days. The exception is materials with a Mohs hardness greater than seven, such as topaz, beryl or tourmaline, which might require extra time to attain a fully-developed polish. In a vibratory tumbler, most materials require just two days to achieve a bright polish. Start inspecting the polish at the end of 24 to 36 hours and stop when the polish is bright. Polishing for extended amounts of time generally does not improve the polish - instead it subjects the rocks to brusing.

Other lapidary uses of cerium oxide:

Cerium oxide is an all-purpose lapidary polish that can be used on wheels and flat laps covered with leather, felt, canvass or other popular coverings. A slurry of cerium oxide and water is applied to the wheel or lap and kept wet during the polish by spritzing with water from a spray bottle. In his book titled "Modern Rock Tumbling," Steve Hart shares that cerium oxide is his "first choice" for most of the harder rocks that he tumbles in a rotary tumbler. He encourages people to try cerium oxide in their vibratory tumbling.

Overspending on cerium oxide?

In the 1960s and 1970s cerium oxide was inexpensive and that is when it reached its peak of use in rock tumbling and other lapidary uses. Today cerium oxide has a lot of competing uses and its price has skyrocketed. Because of its high expense most people now use an aluminum oxide polish such as TXP or #61 Rapid Polish. They produce fantastic results and are much less expensive. We use TXP polish for all of our rotary and vibratory rock tumbling and use #61 Rapid Polish for polishing cabochons on a wheel or a flat lap.

Cerium oxide comes in a wide number of grades. We sell a grade that is appropriate for polishing rocks, minerals and glass in a rock tumbler. The same grade is used by many people for polishing light scratches out of window glass or auto glass. Cerium oxide is also made in grades that are used for polishing high quality mirrors, prisms and telescope lenses. These are extremely expensive. You don't have to buy the most expensive for use in a rock tumbler.

Happy Tumbling!

Article Authored by

Brad Cole Bradley Cole: Bradley is the manager of and has authored much of the content on this website. He also does customer support, photography, maintains the website, and consults with customers about rock tumbler repair and maintenance.
Hobart King Hobart M. King: Hobart is the owner of and has authored much of the content on this website. He has a PhD in geology and is a GIA graduate gemologist. He also writes most of the content for