The tin polishing lap typically refers to a tool used in gem cutting and polishing. It is a type of lapidary equipment used by lapidaries (people who cut and polish gemstones) to shape and polish gemstones. The term "lap" in this context refers to a rotating diskor wheel used for grinding, cutting, or polishing gemstones.tin polishing lap are particularly useful for polishing gemstones that are softer and more delicate, as they provide a gentle and consistent surface for finishing work. Diamond laps are more commonly used for harder gemstones.It's important to note that lapidarywork requires skill and experience to achieve the desired results, as improper polishing can damage or ruin a valuable gemstone.