To polish pure elemental iridium, hot hydrochloric acid is suggested, though the user has not yet tried this method. For hobbyists without a lab, simpler methods using common materials are preferred. Silicon Carbide, known for its hardness, is recommended for grinding iridium, with available sandpaper grits ranging from 100 to 600 or finer at hardware stores. Rock tumblers, especially vibratory types, can be effective for polishing various materials, including metals, and are accessible for hobbyists. Many resources online provide information on rock tumblers and polishing techniques. Additionally, a photo of polished iridium indicates that achieving a mirror finish is possible, potentially using a flat lapping machine.