Cerium Oxide Polishing Compound-One of the Original Rock Tumbler Polishes

What is cerium oxide polish?

Cerium oxide was one of the first polishing compounds to gain widespread use in tumbled stone polishing. It’s the “go-to polish” for many who work with tumbled stone and various gemstones. Cerium oxide imparts a brilliant luster to agate, jasper, quartz, petrified wood, obsidian, feldspar minerals, and virtually any rock, mineral, and glass processed in a tumbled stone machine.

Cerium is a chemical element that, when combined with oxygen, is known as “cerium oxide,” with the chemical composition CeO. It is best suited for materials with a Mohs hardness between 5 and 8.

Polishing Preparation

Most high-quality tumbled stone rough that has been polished with fine grit (500 or 600 grit silicon carbide) is ready for polishing. When we use cerium polish in a tumbled stone machine, we proceed directly from the fine grit step to the polishing stage.

However, some people prefer to perform an ultra-fine grit step (1000 grit silicon carbide) before polishing. This may improve the luster of the tumbled stone or shorten the polishing time, but excellent results can be achieved even without the ultra-fine grit step.



How long does polishing take?

In a rotary polisher, most materials will reach a bright polish in about seven days after adding cerium oxide. The exception is materials with a Mohs hardness greater than 7, such as topaz, beryl, or tourmaline, which may require an additional two days or longer to achieve a fully polished finish.

In a vibratory polisher, most materials with a Mohs hardness of 7 or lower will reach a bright polish in just two days (materials with a Mohs hardness of 8 may require three to four days). Begin checking the polish after 24 to 36 hours and stop when a bright finish is achieved. Polishing for extended periods generally does not improve the finish and may wear the stone down.

Other Uses for Cerium Oxide:

Cerium oxide is a general-purpose gemstone polish that can be used on grinding wheels and leveling discs covered with leather, felt, canvas, or other common coverings. Apply a slurry of cerium oxide and water to the grinding wheel or disc and keep it moist with a spray bottle during polishing.

In his book, Modern Rock Tumbling, Steve Hart shares that cerium oxide is his “go-to” for most harder rocks tumbled in rotary tumblers. He encourages people to try cerium oxide in vibratory tumbling.

Spending Too Much on Cerium Oxide?

In the 1960s and 1970s, cerium oxide was inexpensive, and its use in rock tumbling and other gemstone processing activities reached its peak.

Today, cerium oxide has a wide range of uses, and demand has increased accordingly. Prices have also skyrocketed! Because cerium oxide is expensive, many people now use aluminum oxide polishes, such as TXP or No. 61 Rapid Polish. These generally produce excellent polishes and are much less expensive.

My Experience Using Cerium Oxide

From the 1960s until around 2010, cerium oxide was my favorite gemstone polish. It worked so well that I never thought I’d use anything else. I used it for tumbling, cabochon cutting, and faceting.

Later, in 2010, I purchased some TXP and 61 Rapid Polish from Val Carver. TXP polished all my tumbled stones exceptionally well. 61 Rapid Polish also performed well on my cabochons and flats. Therefore, due to the high price of cerium oxide, I stopped using it. Now, I am almost always satisfied with TXP and 61 Rapid Polish.

The only exception is if my material has fine cracks. The particles of 61 Rapid Polish are small enough to penetrate these cracks and leave a white line on the stone caused by the accumulation of particles in the cracks. I have learned to use TXP for these materials because of its larger particles (TXP’s particle size distribution is concentrated around 3 microns, while 61’s particle size distribution is concentrated around 0.3 microns).

Various Grades of Cerium Oxide Polish

Cerium oxide comes in several grades. We sell a grade suitable for polishing rocks, minerals, and glass with a polishing machine. Many people also use this grade to polish minor scratches on car windows or automotive glass.

Cerium oxide also comes in high-quality grades used for polishing high-quality lenses, prisms, and telescope lenses. These grades are quite expensive. You don’t have to buy the most expensive grades to make a rock polisher.

A Note on the Color of Cerium Oxide Polish

Pure cerium oxide polish is typically white. As its purity decreases, the color gradually changes from white to yellow, and then to orange or pink.