In order to develop smoothly polished sapphires, you'll need to place your rock tumbler in an area where it won't be agitated. Since tumbling any type of rocks can take a few weeks to tumble, you may also need to consider keeping your tumbler in a quiet area of your home, such as your garage. You don't need to buy top quality sapphires when tumbling your stones.
Choose sapphires of varying sizes. Using sapphires that are the same size will cause your tumbler to to make your stones less polished in appearance.
Use a grit that is harder than sapphire on the Mohs scale of mineral hardness, which measures scratch resistance. According to Rock Tumbling Supplies, use silicon carbide, which has a hardness of 9.25 as compared with sapphire's rating of 9.
Load your tumbler with your sapphires. Fill the tumbler with water. Your tumbler should be at least half to three-quarters full of water.
Turn your tumbler on for a week. Check on your tumbler every day to ensure that there isn't any water leaking out. Always ensure that your tumbler remains half full through the tumbling process.
Fill your tumbler with the silicon carbide grit after a week's time has passed. Use four tablespoons of grit. Ensure that your tumbler is half to three-quarters full. Let your sapphires tumble for another five to seven days.
Remove any excess water from your tumbler once the week has passed. Use a hand towel to clean out left over grit within your tumbler. Begin to dig out your tumbled rocks. Discard any rocks that are broken down or cracked.
Check your sapphires for the quality of smoothness. If your rocks have pits or are still rough in appearance, repeat step five.