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How Do I Polish Garnets?

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Garnet, the January birthstone, comes in a wide variety of color, from dark red to bright yellow green. Garnets can be found naturally in parts of Africa, the United States, Canada, India, Madagascar, Sri Lanka and Brazil. The durability and bright colors exhibited by garnets make them a favorite among rock collectors and amateur geologists alike. Polishing a garnet found in the wild can reveal the brilliant color of your gemstone and even make it an attractive jewelry piece.


If you do not own a gemstone and rock tumbler, purchase one from a hobby store or through an online hobby retailer. Purchase a high quality tumbler; garnets have a hardness of 7.5, which is higher than most gemstones. Additionally, you could purchase a phenolic lap for the final polish stage. Phenolic laps can withstand the use of high quality polishing compounds, such as diamond or alumina oxide.

Stages of Grit

Polish your garnets in four stages with different grades of grit. Begin tumbling your garnets in a tumbler with coarse grit for at least one week. Use medium to fine grit in the second stage of tumbling, which should last for at least one week. Use pre-polish for a week and a half in the third stage of tumbling, and leave rocks in the fourth stage to tumble in polishing compound for at least two weeks. Follow manufacturer directions pertaining to the amount of grit to use for each stage.

Normal tumbling guidelines recommend four to six weeks for tumbling, but garnets may need more time due to their hardness. Keep your tumbler two-thirds full with stones and water. Use just enough water to cover your garnets.

Between Stages

Thoroughly wash your tumbling materials, including garnets, between tumbling stages to prevent garnet scratches caused by coarse grit residue. Wash your garnets as soon as you remove them from the tumbler. Remove any garnets that are broken, have sharp edges or are smaller than one-quarter inch.

When washing coarse grit residue, do not use your sink; the coarse grit may clog a drain. Use a mesh material that you can hang from outdoor fixtures such as trees or wooden stakes. Place your garnets on the mesh so they are suspended above ground and spray with a hose. Save some of the mesh material when washing away other grades of grit into your sink.

If possible, remove the barrel from the tumbler and wash it thoroughly. Any residue left from higher grades of grit can damage your garnets during later polishing stages.

Final Polish

Use a different tumbler barrel for the final polishing stage. This will reduce the risk of possibly tainting the final polishing stage with higher grades of grit. Wash your garnets and the barrel thoroughly after finishing the polishing stage. You can refill the barrel with your garnets, warm water and soap or a non-corrosive detergent for a brighter polish. Let these materials tumble for about eight hours.

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