Cerium Oxide PolishOptical grade cerium for use on all quartz, agate and jasper. It also produces a great polish on petrified wood, coral, obsidian and man made glasses including goldstone. Many people prefer cerium for tumbling feldspar materials such as moonstone, labradorite, sunstone and amazonite. 1. 5 microns average particle size. Polish is beige in color. Recommended to use about one tablespoon per pound of rock.