The Star-shaped Ore is a quest item from The Legend of Zelda: Oracle of Seasons. It is one of five types of ore Link can find in Subrosia. It can be found randomly by digging in Subrosia Seaside and is used to purchase a new Ribbon for Rosa. In gratitude, Rosa goes on a date with Link, during which Link can use her key necklace, allowing him to unlock the door to the Tower of Summer in the Temple of Seasons.
Although they serve no further purpose after obtaining the Ribbon, it is interesting that multiple Star-shaped Ores can be found.